Binder2 KUL MIS Book

FROM THE FOREWORD . . .“With surgical techniques being the emphasis, a broad range of clinicians can effectivelyimplement various aspects of the book’s contents. Minimally Invasive Spinal FusionTechniques is thus a welcome addition to the professional literature to help advance the surgical understanding and continued progress of this exciting and fast moving field.”

— Dr. Heinz Michael Mayer, Orthopedic Hospital (Müchen, Germany)

ABOUT THE BOOK . . .Several surgery technologies have recently emerged which have led many Spinal Surgeons torethink traditional approaches to reconstructive procedures of the spine. Minimally invasivespinal surgery (MISS) techniques are now aided by computerized navigation systems, alongwith improved and more flexible instrumentation and surgical systems. Minimally InvasiveSpinal Fusion Techniques provides the medical professional with a thorough review of preclin-ical and clinical data while describing and illustrating the most effective surgical techniquesthus far employed. Objectively reviewing the most current treatment methods for patients withdegenerative conditions of the cervical and lumbar spine, this timely reference book spans thebreadth of minimally invasive spinal fusion and related methodologies that have been performed surgically to date, as well as its future as an ongoing medical treatment.

ABOUT THE EDITORS . . .Kai-Uwe Lewandrowski is a Clinical Assistant Professor at the University of Arizona and isin private practice at the Center for Advanced Spinal Surgery of Southern Arizona in Tucsonspecializing in MISS treatments for degenerative conditions, tumor, and trauma. He receivedhis MD from Humboldt University (Berlin, Germany), completed a residency at MassachusettsGeneral Hospital, and a fellowship in Spinal Surgery at the Cleveland Clinic. Dr. Lewandrowskihas served as lead Editor on such medical books as Advances in Spinal Fusion (2003) andSpinal Reconstruction (2006).

Christopher A. Yeung is a practicing Orthopedic Spine Surgeon at the Arizona Institute for Minimally Invasive Spine Care in Phoenix where he specializes in MISS techniques, especially relating to sports related spine injuries. Dr. Yeung received his MD from Universityof Southern California, completed a Orthopedic residency at UC-Irvine, and a Spine fellow-ship at UC-San Diego.

Mark J. Spoonamore is Assistant Professor of Clinical Orthopedic Surgery at the Universityof Southern California in Los Angeles where he specializes in MISS, as well as sports spinalinjuries and rehabilitation. Dr. Spoonamore received his MD from the University of Illinois atChicago, completed an Orthopedic Surgery residency at the University of Iowa, and a SpineSurgery fellowship at USC.

Robert F. McLain is on the staff of the Department of Orthopedic Surgery at the ClevelandClinic Foundation (Cleveland, Ohio). He is a well published authority regarding both micro-surgical and minimally invasive spine techniques. Dr. McLain serves as Associate Editor forthe journal, Spine. Prior to joining Cleveland Clinic in 1997, Dr. McLain was the Director of theSpine Care Center at UC-Davis.

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Common Patient Misperceptions andFears of Spinal Fusion Surgery

1 Kai-Uwe Lewandrowski

n THE EDUCATED PATIENT

Today, lumbar spinal fusion surgery is dramatically different even from 10 yearsago. Countless technical innovations and advances in implants and surgical pro-cedures have drastically changed the way spine surgeons now address degen-erative conditions of the lumbar spine.

Much has changed since the initial description of the posterior lumbarinterbody fusion (PLIF) by Q1Cloward. Due to the advent of pedicle screws andinterbody fusion implants, surgical techniques such as PLIF and transforaminallumbar interbody fusion (TLIF) have gained tremendous popularity due to thesurgeon’s ability to adequately address the patient’s symptoms by decompressionof neural elements, by restoring spinal segmental stability, and by improvingsaggital alignment (1–7).

As a result, the number of single- and multilevel-instrumented PLIF andTLIF procedures has dramatically increased in the past 10 years. However, this alsohas resulted in a surge in the problems and complications associated with theseprocedures. These complications include nerve root injuries, failure of fusion,implant migration and breakage, transition problems at the level adjacent to afusion, and poor restoration of lumbar lordosis. The latter problem of saggitaldecompensation is poorly tolerated by patients.

Patients’ perception of clinical success rates and functional outcomes withlumbar spinal surgery is frequently biased by anecdotal information obtained fromfamily members, friends, and colleagues. Therefore, spine care providers are oftenconfronted with disbelief and skepticism when consulting patients on optimaltreatment of their condition.

Nowadays, patients are frequently well educated about their clinicalcondition, and have done extensive research prior to entering a spine care provider’soffice. They are often deterred by the obvious drawbacks to conventional openposterior approaches to the lumbar spine, such as persistent low-back pain causedby iatrogenic muscle denervation. It is well recognized that this approach-relatedproblem may result in atrophy and decreased trunk extensor strength (8–10).Therefore, patients expect spine surgeons to keep up with the development ofalternative, less aggressive, and minimally invasive procedures similar to othersurgical subspecialties, where endoscopic and mini-open procedures are well

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Kai-Uwe Lewandrowski Center for Advanced Spinal Surgery of Southern Arizona, Tucson,Arizona, U.S.A.

1

established and now are the accepted standard of care. Only this phenomenon canexplain why there is such an ongoing renaissance of mini-open Wiltse-typeexposures, or true percutaneous approaches to spinal pathology (8–14).

n PATIENT EXPECTATIONS AND SATISFACTION POST-PROCEDURE

It has been well documented that patient expectations of a given intervention orsurgical procedure is clearly related to the established success rate of the treatment(15). It is also quite evident that patient satisfaction with their surgical procedure isrelated to their expectations prior to surgery (15–18).

As said above, expectations are dependent on established success rates, thequality of care provided, the extent of patient education prior to surgery,personality traits, the overall health and mood status of the patient, and, last butnot least, information obtained from relatives and friends (16,19–21). In support ofthat statement is research conducted on patients after total joint arthroplasty anddecompression for spinal stenosis. If expectations are unrealistic about the outcomeof the surgical procedure, these patients will have an inferior level of satisfaction(21,22). Conversely, patients with adequate preoperative education and appro-priate level of expectations have been shown to have shorter recovery time,improved health status and function, and a higher level of satisfaction whenundergoing decompression for lumbar herniated nucleus pulposus (15).

n COMMON MISCONCEPTIONS

Although there is no formal analysis of the problem, and a patient’s decision-making process can be very complex, there are some common recurrent concernsthat have been voiced by patients in my practice whenever they are facing spinalsurgery. Realizing that my personal expert opinion represents the lowest level ofscientific evidence, it still seems worthwhile to mention some of these concerns,since they do not seem to be unique to anyone’s spine practice:

n “Spinal surgery is too dangerous, delicate, and complex. . . I much rather livewith the symptoms than exposing myself to the risks of spinal surgery.”

n “Spinal surgery is associated with large amount of blood loss due to longincisions, and lengthy procedures.”

n “ I should not have a spinal fusion since my bone graft harvest site will hurtmore than I hurt now.”

n “At best, spinal surgery only works temporarily and it always seems to snowball into more trouble.”

n “ I know someone who had spinal surgery and he/she is much worse off thanbefore the surgery.”

n “ If I have this fusion surgery now, when will I need the next surgery?”

This list of anecdotal patient concerns could be continued, and many of mycolleagues have heard them in one form or another. Although spine care providersand surgeons may despise patients for critically questioning their clinical decisionmaking (“I am the surgeon and I know what’s best for you”), the fact remains thatthe patient’s fears and apprehension toward spinal surgery are a reflection of theshortcomings of our clinical outcomes with the spinal fusion procedure.

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2 n Lewandrowski

n ADVANCES IN SPINAL FUSION SURGERY

Recognizing patients’ demands, several surgeons have developed minimallyinvasive surgical approaches to the lumbar spine to minimize the approach-relatedmorbidity associated with the procedure (23–29). Today, multiple systems areavailable for percutaneous pedicle screw insertion and rod delivery usingfluoroscopy or navigation technology (28,29).

The METRx± (Medtronic Sofamor Danek) tubular retractor system wasintroduced by Foley and Smith in 1997. This innovative, minimally invasive accessportal to the lumbar spinal initiated the development of a whole array of minimallyinvasive surgeries by allowing for comprehensive decompression of neuralelements. Several important technical advances have been adopted in clinicalpractice (24,25). Of these, percutaneous insertion of pedicle screws and interbodyfusion cages, biplanar fluoroscopy, fluoronavigation, and image guidance naviga-tion techniques are some of the more significant recent advances.

The clinical merit of these new procedures is now emerging in the literature.For example, Isaacs et al. (27) reported their results with percutaneous pediclescrew-rod fixation and interbody cage insertion through a 20-mm tubular access.As expected, several advantages regarding intraoperative blood loss, transfusionrate, and postoperative in-hospital days were demonstrated in comparison withopen, posterior interbody fusion procedures (27).

Patients are increasingly realizing that conventional, open midline ap-proaches produce extensive muscle and soft tissue dissection simply to gain accessto the pathology and in some cases to gain access to anatomical landmarks toidentify the entry points for the insertion of pedicle screws and the disc space. Theyare increasingly aware of the fact that extensive dissection lateral to the facet jointsmay produce fatty degeneration of paraspinal muscles. This has been welldocumented for the multifidus muscle, which Q2has been shown to degenerate bydisruption of its vascular and nervous supply (30–32). This problem may producedecreased trunk extensor strength and, potentially, chronic back pain (29,32).

Although there were attempts at treating spinal pathology with minimallyinvasive techniques in the later 1970s and 1980s, most of these earlier techniqueshad fallen out of favor because of technical limitations, and unacceptable failureand complication rates. This statement holds particularly true for the percutaneouschemonucleolysis (33–35) and other automated percutaneous techniques (36).Today, there is a resurge of minimally invasive techniques largely driven by patientexpectations and technological advances. This trend has stimulated this text whichaims at highlighting some of the key areas of this fast-moving field.

n REFERENCES

1. Boden SD, Andersson GB, Fraser RD, et al. Selection of the optimal procedure toachieve lumbar spinal fusion. Introduction. 1995 Focus Issue Meeting on Fusion. Spine1995; 20 (Suppl. 24):166S.

2. Brantigan JW, Steffee AD, Lewis ML, Quinn LM, Persenaire JM. Lumbar interbodyfusion using the Brantigan I/F Cage for posterior lumbar interbody fusion and thevariable pedicle screw placement system: two-year results from a Food and DrugAdministration investigational device exception clinical trial. Spine 2000; 25:1437–46.

3. Escobar E, Transfeldt E, Garvey T, Ogilvie J, Graber J, Schultz L. Video-assisted versusopen anterior lumbar spine fusion surgery: a comparison of four techniques andcomplications in 135 patients. Spine 2003; 28:729–32.

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Common Patient Misperceptions and Fears of Spinal Fusion Surgery n 3

4. Moskowitz A. Transforaminal lumbar interbody fusion. Othop Clin North Am 2002; 33:359–66.

5. Pradhan BB, Nassar JA, Delamarter RB, Wang JC. Single-level lumbar spine fusion: acomparison of anterior and posterior approaches. J Spinal Disord Tech 2002; 15:355–61.

6. Rosenberg WS, Mummaneni PV. Transforaminal lumbar interbody fusion: technique,complications, and early results. Neurosurgery 2001; 48:569–75.

7. Whitecloud TS 3rd, Roesch WW, Ricciardi JE. Transforaminal interbody fusion versusanterior-posterior interbody fusion of the lumbar spine: a financial analysis. J SpinalDisord 2001; 14:100–3.

8. Elias WJ, Simmons NE, Kaptain GJ, Chadduck JB, Whitehill R. Complications ofposterior lumbar interbody fusion when using a titanium threaded cage device. JNeurosurg 2000; 93(Suppl. 1):45–52.

9. Hee HT, Castro FP Jr, Majd ME, Holt RT, Myers L. Anterior/posterior lumbar fusionversus transforaminal lumbar interbody fusion: analysis of complications andpredictive factors. J Spinal Disord 2001; 14:533–40.

10. Humphreys SC, Hodges SD, Patwardhan AG, Eck JC, Murphy RB, Covington LA.Comparison of posterior and transforaminal approaches to lumbar interbody fusion.Spine 2001; 26:567–71.

11. Kawaguchi Y, Matsui H, Tsuji H. Back muscle injury after posterior lumbar spinesurgery. A histologic and enzymatic analysis. Spine 1996; 21:941–4.

12. Kawaguchi Y, Yabuki S, Styf J, et al. Back muscle injury after posterior lumbar spinesurgery. Topographic evaluation of intramuscular pressure and biology flow in theporcine back muscle during surgery. Spine 1996; 21:2683–8.

13. Sihvonen T, Herno A, Paljarvi L, Airaksinen O, Partanen J, Tapaninaho A. Localdenervation atrophy of paraspinal muscles in postoperative failed back syndrome.Spine 1993; 18:575–81.

14. Weber BR, Grob D, Dvorak J, Muntener M. Posterior surgical approach to the lumbarspine and its effect on the multifidus muscle. Spine 1997; 22:1765–72.

15. Lutz GK, Butzlaff ME, Atlas SJ, et al. The relation between expectations and outcomesin surgery for sciatica. J Gen Intern Med 1999; 14:740–4.

16. de Groot KI, Boeke S, Passchier J. Preoperative expectations of pain and recovery inrelation to postoperative disappointment in patients undergoing lumbar surgery. MedCare 1999; 37:149–56.

17. Iversen MD, Daltroy LH, Fossel AH, et al. The prognostic importance of patient pre-operative expectations of surgery for lumbar spinal stenosis. Patient Educ Couns 1998;34:169–78.

18. Nettleman MD. Patient satisfaction—What’s new? Clin Perform Qual Health Care 1998;6:33–7.

19. Mancuso CA, Altchek DW, Craig EV, et al. Patients’ expectations of shoulder surgery. JShoulder Elbow Surg 2002; 11:541–9.

20. Mancuso CA, Salvati EA. Patients’ satisfaction with the process of total hip arthroplasty.J Healthc Qual 2003; 25:12–18.

21. McGregor AH, Hughes SP. The evaluation of the surgical management of nerveroot compression in patients with low back pain. Part 2: patient expectations andsatisfaction. Spine 2002; 27:1471–6.

22. Haddad FS, Garbuz DS, Chambers GK, et al. The expectations of patients undergoingrevision hip arthroplasty. J Arthroplasty 2001; 16:87–91.

23. Fessler RG, Khoo LT. Minimally invasive cervical microendoscopic foraminotomy: aninitial clinical experience. Neurosurgery 2002; 51(Suppl. 5):S37–S45.

24. Foley KT, Gupta SK. Percutaneous pedicle screw fixation of the lumbar spine:preliminary clinical results. J Neurosurg 2002; 97(Suppl. 1):7–12.

25. Foley KT, Smith MM. Microendoscopic discectomy. Tech Neurosurg 1997; 3:301–7.26. Guiot BH, Khoo LT, Fessler RG. A minimally invasive technique for decompression of

the lumbar spine. Spine 2002; 27:432–8.27. Isaacs RE, Podichetty VK, Santiago P, et al. Minimally invasive microendoscopy-

assisted transforaminal lumbar interbody fusion with instrumentation. J NeurosurgSpine 2005; 3:98–105.

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4 n Lewandrowski

28. Khoo LT, Palmer S, Laich DT, Fessler RG. Minimally invasive percutaneous posteriorlumbar interbody fusion. Neurosurgery 2002; 51(Suppl. 5):S166–S181.

29. Perez-Cruet MJ, Foley KT, Isaacs RE, et al. Microendoscopic lumbar discectomy:technical note. Neurosurgery 2002; 51(Suppl. 5):S129–S136.

30. Kader DF, Wardlaw D, Smith FW. Correlation between the MRI changes in the lumbarmultifidus muscles and leg pain. Clin Radiol 2000; 55(2):145–9.

31. Kawaguchi Y, Matsui H, Tsuji H. Back muscle injury after posterior lumbar spinesurgery. Part 1: histologic and histochemical analyses in rats. Spine 1994; 19(22):2590–7.

32. Parkkola R, Rytokoski U, Kormano M. Magnetic resonance imaging of the discs andtrunk muscles in patients with chronic low back pain and healthy control subjects.Spine 1993; 18(7):830–6.

33. Herkowitz HN. Current status of percutaneous discectomy and chemonucleolysis.Orthop Clin North Am 1991; 22(2):327–32.

34. Diagnostic and therapeutic technology assessment. Percutaneous lumbar diskectomyfor herniated disks. JAMA 1989; 261(1):105–9. Erratum in: JAMA 1989; 261(20):2958.

35. Maroon JC, Onik G, Sternau L. Percutaneous automated discectomy. A new approach tolumbar surgery. Clin Orthop Relat Res 1989; (238):64–70.

36. Helms CA, Onik G, Davis GW. Automated percutaneous lumbar discectomy. SkeletalRadiol 1989; 18(8):579–83.

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Common Patient Misperceptions and Fears of Spinal Fusion Surgery n 5

Nonendoscopic Percutaneous DiscDecompression Treatment of DiscogenicLumbosacral Radiculopathy

2 Michael J. DePalma and Amit Bhargava

n INTRODUCTION

Lumbar pain and sciatica are responsible for a significant portion of health careexpenditure, afflicting approximately 10 million individuals at an estimated cost ofseveral billion dollars in diagnosis, treatment, and lost wages (1,2). A variety ofspinal structures can serve as the source of incapacitating lumbar pain. However,the lumbar intervertebral disc has been demonstrated to be the most commoncause of chronic low-back pain (3). Lower-limb pain in the presence of lumbar painmay be somatically referred from deep spinal structures (4) or may be themanifestation of nerve root insult (5). Intervertebral disc herniation has long beenrecognized as a common source of neural injury (6,7), and can present as lower-limb pain with or without motor or sensory deficits (8). Radicular signs andsymptoms are addressed in a therapeutically different fashion compared to axialdiscogenic symptomatology. These treatment measures have been molded by theprevailing theory of spinal pathophysiology.

Biomechanical compression of neural elements has long been viewed as thesole etiologic factor leading to the manifestation of signs and symptoms (6).However, there is evidence that mechanical influence is not the sole etiologic factor(9–18). There is little correlation between the severity of radiculopathy and the sizeof the disc herniation (10,13,14,19). Resolution of symptoms after conservativetreatment has been observed without a concurrent reduction in disc herniationvolume (13,14). It is probable that, in most instances, biomechanical injury is notthe sole cause of lumbar radicular symptoms related to lumbar intervertebral discherniation (16,17,20–26).

The natural history of radiculopathy due to a herniated intervertebral disctreated conservatively including spinal injections is marked by gradual improve-ment over a period of a few weeks to three to five months (27–34). Over this timeperiod, 50% to 60% of these herniations will resolve to a variable degree(13,14,31,35). Asymptomatic lumbar disc herniations have been documented(9,11,12,36). Thus, the extension of nuclear material through a rent in the annularfibers presumably represents a reversible anatomical abnormality responsible forlimb pain due to nerve root insult. Such an injury results in both biochemical and

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Michael J. DePalma Sheltering Arms Spine and Sport Center, Department of Physical Medicineand Rehabilitation, Virginia Commonwealth University, Richmond, Virginia, U.S.A.Amit Bhargava, University of Maryland School of Medicine, Department of Orthopedics andRehabilitation, Baltimore, Maryland, U.S.A.

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biomechanical harassment of the spinal nerve root. Over a period of time, both oreither of the biomechanical and biochemical insults will abate, allowing forresolution of signs and symptoms of nerve root injury. In this sense, a componentof the disc herniation pathophysiology will effectively reverse. Whether or not theassociated nerve root injury reverses depends on the level of nerve injury(neurapraxia vs. axonotmesis) (37). If symptoms persist despite physical therapy,oral anti-inflammatory medications, and a tincture of time, fluoroscopicallyguided transforaminal epidural corticosteroids (TFESIs) or selective nerve rootinjections (SNRIs) (Fig. 1) are the appropriate next step in the treatment algorithm(28,29,31,32). The majority of patients’ symptoms will improve with one to fourinjections (34,38,39), as the inflammatory response of the herniation is renderedinert. The remaining one-quarter to one-third of patients who do not respond to

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FIGURE 1(A) Fluoroscopic image of a right L5 TFESI. Notice the contrast in spread medial

and cephalad to the right L5 pedicle. (B) Fluoroscopic image of a right L5 SNRI. Notice theperineural outline of the exiting nerve root and spinal nerve. Abbreviations: TFESI,transforaminal epidural steroid injection; SNRI, selective nerve root injection.

8 n DePalma and Bhargava

conservative care and do not appreciate a steroid benefit from TFESIs and/orSNRIs may require mechanical decompression of the offended nerve root(s) inorder to alleviate the neural compression and the source of inflammation (29–32).

Open surgical discectomy has traditionally been the standard of care forpersistent radicular limb pain due to a herniated intervertebral disc (6). Althoughsurgical results have been quite successful (40,41), open surgery is not withoutrisks (42–44). Prospective trials have observed a major complication rate of 1.6%(42) to 13% (43), ranging from major neurologic injury (42) and nerve injury (43),discitis (43), to intraoperative death (42,43). The advent of the microdiscectomytechnique has not decreased the surgical complication rate. Pappas et al. observeda rate of complication of 10.8%, including two vascular injuries, one fatal, and amajor injury in 654 cases (44). Reoperation rates for recurrent disc herniation rangefrom 5% to 21% (45–49). Primary protrusions without an anular defect are morelikely to require revision surgery than extruded or sequestered disc fragments(45,49). Despite the favorable natural history of discogenic radiculopathy (29–31), aprotracted conservative regimen addressing severe radicular symptoms should beavoided to maximize the odds for a successful outcome (50). Treatment for acontained herniation-induced radiculopathy unresponsive to physical therapy, oralanti-inflammatory medications, and spinal injections might best be achieved byone of a variety of percutaneous disc decompressive techniques (51–95). Discdecompression via the percutaneous approach (Figs. 2 and 3) has been pursued asa means by which to decompress a reversible anatomical defect alleviating neuralinjury with less morbidity and mortality than the open surgical approach.

The predominant indication for decompression remains limb pain due to areversible anatomic source (51–54,59,60,69,77,79,81,90–95). Some studies fail to

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FIGURE 2Photograph of patient set-up for lumbar percutaneous disc decompression.

Nonendoscopic Percutaneous Disc Decompression Treatment n 9

differentiate these two symptomatically distinct groups (61,65,68,75,80,88,89); inthese studies, meaningful conclusions regarding treatment efficacy are difficult toformulate. Consequently, the use of percutaneous disc decompressive proceduresto treat solely axial pain remains speculative, with less structured support thansimilar treatment for discogenic radiculopathy. Because of such difficulties, this

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FIGURE 3(A) Anteroposterior, (B) lateral, and (C) oblique views of a schematic of cannula

placement within the L5-S1 intervertebral disc.


chapter will not attempt to discuss the efficacy of nonendoscopic percutaneousdecompressive techniques (Fig. 4) for axial pain, but will focus primarily onefficacy and safety for limb pain.

n EFFICACY AND COMPLICATIONS BY TECHNOLOGY

ENZYMATIC DEGRADATION—CHYMOPAPAINChymopapain is a protease derived from the latex of the papaya tree and was firstisolated by Jansen and Balls 65 years ago (96). The enzyme acts exclusively on thenuclear noncollagen ground substance and reduces glycosaminoglycans andwater, resulting in volume reduction (97). Q1The efficacy of intradiscal chymopapainin treating lumbar radiculopathy due to herniated intervertebral discs was firstreported by Lyman Smith in 1964 who coined the term “chemonucleolysis” (98).

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FIGURE 4(A) Anteroposterior and (B) lateral fluoroscopic views of placement of a 1.5mm

Dekompressor cannula within the central third of the L5-S1 intervertebral disc.


Since this initial investigation, intranuclear injection of chymopapain has becomethe most extensively evaluated and regulated minimally invasive intervention forradicular pain recalcitrant to conservative treatment (99). Despite 42 years ofclinical and basic science research, chemonucleolysis remains a controversialtreatment for discogenic radiculopathy (99).

Five randomized, controlled trials have been performed attesting tochemonucleolysis’ efficacy. Schwetschenau et al.’s initial trial in 1976 (100) foundno statistically significant difference favoring chymopapain. However, this studyhas been criticized for using a therapeutically active placebo, inadequatechymopapain dose, improper needle placement, and improper breaking of therandomization code (51,52).

Four subsequent investigations have since established the therapeuticefficacy of chemonucleolysis (51–54). Javid et al. engineered a much more soundstudy in which 55 patients with persistent signs and symptoms of radiculopathywere randomized to receive 3mL of chymopapain (3000 units/1.5mL) while53 patients were randomized to 3mL of pyrogen-free saline (51). Outcomes weremeasured primarily at six weeks and six months by assessing improvement inradicular signs and symptoms, and subjective improvement as deemed by thepatient and physician. About 82% of the chymopapain patients had a successfulclinical course in contrast to just 41% of the placebo group. The remaining 59%crossed-over to the chymopapain arm, and 91% of these cases were thensuccessfully treated.

Fraser published two-year data after randomizing 30 patients to receive2mL (8mg) of intradiscal chymopapain and 30 patients to receive 2mL ofintradiscal saline (53). Each patient had not responded to 6 to 24 weeks ofconservative care including physical therapy. Outcomes were measured by painrating and the patient’s subjective report of the treatment assessed at six monthsand again at two years, while maintaining blinding of both the investigator andthe patients. All 60 initial patients were evaluated at both follow-up intervals.Seventy-three percent of the chymopapain group versus 47% of the controlgroup felt the treatment was successful at two years. Fifty-three percent of thetreatment group was pain free at two years compared to 23% in the salinegroup. At the time of follow-up, 40% of the saline group and just 20% of thechymopapain group had required laminectomy. Fraser’s work provided the firstprospective, controlled, long-term follow-up data demonstrating a sustainedtherapeutic benefit of chymopapain in the treatment of lumbosacral radiculo-pathy due to disc herniation.

Three years later, Dabezies et al. published the largest prospective,randomized, controlled trial of 173 patients suffering from lower-limb radicularpain recalcitrant to at least two weeks of conservative care (52). Eighty-sevenpatients received 2mL (8mg) of chymopapain, and 86 received an equivalentvolume of cysteine–edetate–iothalamate in a randomized fashion. Patients wereassessed at six weeks, three months, and six months after intervention, andimprovement was defined by subjective improvement in pain, normalization ofneurologic findings, and a return to previous level of occupation. This studycontained an inordinately large number of code breaks as patients requested tobecome unblinded in order to pursue chymopapain treatment once the sponsorannounced it would afford all patients in the placebo arm the opportunity to travelout of the country for treatment. Including the results after the code breaksrevealed a successful outcome in 71% in the treatment arm compared to 45% in the

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control group at six months. These numbers changed to 67% and 44% respectively,if the code-break patients were excluded from data analysis. These findings arecommensurate with previously published studies (51,53).

Gogan and Fraser published 10-year-data of their 60 patients initially studiedat six months and two years (54). All the patients had remained blinded to theidentity of their intervention and were assessed by an independent observer whowas unaware of the original therapy. Eighty percent of the chymopapain patientsand 34% of the saline group found their treatment successful. Of the chymopapaingroup, 53% were completely pain free at 10 years in contrast to 23% of the salinegroup at 10 years. Six of the 30 chymopapain patients eventually underwent opensurgical discectomy at the treated level, but none of these cases occurred two yearsafter treatment. In short, 77% of the chymopapain patients and 38% of the salinepatients achieved a good result at 10 years (54).

The efficacy of chemonucleolysis appears to compare well with that of opensurgical discectomy (55,56). Outcomes at one year were not significantly differentbetween patients treated with chemonucleolysis and those with open surgicaldiscectomy in a randomized, prospective, controlled trial (56). However, this trialdid show a statistically significant difference at six weeks and three monthsin favor of the surgical group (56). In Nordby’s experience, good to excellentresults occurred at six weeks in 80% of 100 patients treated with chemonucleolysis.Eighty-five percent of their 100 surgical counterparts experienced good to excellentresults at six weeks. Although open surgical discectomy was statistically superior(p ¼ 0.13) to chemonucleolysis at six weeks, no statistical difference was measuredat six months or one year (99). In a retrospective review 10 years after treatment,Tregonning et al. observed a minimal difference in efficacy between 145 patientstreated with chymopapain and 91 patients treated surgically (57). Overall, themean success rate of chemonucleolysis has been calculated as 66% compared to77% for open surgical discectomy (55). Taking into account the similar efficaciesbetween chemonucleolysis and open surgical discectomy, the former may be morecost effective in treating discogenic lumbosacral radiculopathy due to the lowerassociated costs (58).

The overall complication rate of chemonucleolysis has been calculated to be3.7%, with the rate of severe complications being 0.45% (101). However, thiscalculation may be an overestimate. Data reported to the Food and DrugAdministration (FDA) revealed 121 adverse reactions in approximately 135,000 pa-tients (102). Of these 121 adverse events (102), 7 cases were fatal anaphylaxis, 24were infection, 32 were hemorrhage, 32 were neurologic deficits (such asparaplegia, paraparesis, hemiparesis, and foot drop), and 15 were miscellaneouscases of cardiac and respiratory complications. The overall mortality rate was0.019% (102). The most common side effect is backache and stiffness ranging from15% (51) to 100% (98). Lumbar muscle spasm or guarding has been observed in36% to 41% of patients treated with chymopapain (51). Discitis (53,54), lower-limbdeep venous thrombosis (54), anaphylactic shock and death (61), acute transversemyelitis (61) [a causal relationship between chymopapain and central nervoussystem could not be substantiated (103)], and cerebral hemorrhage (104) have beenrarely reported. Anaphylaxis was recognized in 1 of 87 patients receivingchymopapain in Dabezies’ 1987 study (52). However, since then, the incidence ofanaphylactic reactions has decreased to 0.25%, due to sensitivity testing andantihistamine administration preinjection (99). No epidural or intraneural fibrosishas been observed (52).

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MECHANICAL DECOMPRESSION—AUTOMATEDPERCUTANEOUS DISCECTOMYAlthough chemonucleolysis has been well studied, with strong evidence attestingto its efficacy, its use has fallen out of favor because of concerns over catastrophiccomplications. By 1994, most centers in the United States had discardedchemonucleolysis as a means to decompress a herniated intervertebral discbecause it was perceived as less effective than standard open discectomy, and theassociated complication rates were higher than could be accepted on the basis ofthis efficacy (105). Consequently, in late 1999, Boots Pharmaceuticals halted themanufacturing and distribution of its chymopapain product (64). Alternativemeans to achieve mechanical decompression of the herniated disc percutaneouslywere pursued. Pioneering investigations of mechanical percutaneous discdecompression initiated in the mid-1970s (62) incorporated large cannulas, withan associated risk of nerve injury, and required involved modified pituitaryforceps, which proved to be cumbersome and time consuming (62,63). In 1984,Onik et al. introduced an automated percutaneous device by which tomechanically remove herniated nuclear material in order to decompress theaffected nerve root (61). Using this technique, a 2-mm, 8-inch long blunted closed-tip probe containing a side port with a reciprocating blade (Fig. 5) is placed withinthe nucleus. Suction is applied through the inner cannula to pull nuclear materialinto the port. The sharpened end of the inner cannula is pneumatically drivenacross the port, severing the aspirated nuclear material from the parent source. Theremoved nuclear material is then aspirated into a collection container (61).

In a prospective study of 518 patients, Davis and Onik (66) demonstrated asuccess rate of 85% at a minimum follow-up of one year after removing a mean of2.1 g of nuclear material. Patients were evaluated at three-month intervals up totwo years after the procedure. However, data from evaluations prior to one yearwere not presented in the paper; yet, the authors did comment that 70% ofsuccessfully treated patients returned to work within two weeks (66). The absenceof the postprocedure data at the three-month intervals prevents an assessment ofthe rate of improvement, which might allow commentary regarding the efficacyof the intervention relative to the natural history of the condition. A regressiontoward the mean analysis might have proven helpful in demonstrating a plateau ofthe patients’ signs and symptoms prior to treatment, since no control group wasavailable for comparison.

In a large prospective study of 1525 patients, Teng et al. found a success rateof 83%: 56% of patients became pain free and 26% of patients greatly improved, at amean follow-up of 18.3 months, with 51 patients being lost to follow-up (106).The authors treated 1289 patients presenting with sciatica and 185 patientspresenting with complaints of primarily low-back pain. These diagnosticcategories were not separated prior to data analysis. Patients had persistentsymptoms after a minimum of two months of conservative care and demonstrateda corroborative disc herniation on MRI or CT.

In a prospective assessment of over 1350 patients treated with automatedpercutaneous lumbar discectomy APLD Bonaldi (68) observed Q2successful out-comes in 67.5% of patients at six months. He found favorable results in certainsubgroups (68). Almost 80% of 83 elderly patients 70 years or older experiencedgood or excellent results, and 78% of 108 postsurgical patients suffering a recurrentdisc herniation at the previously treated level appreciated good or excellent results(68). His technique included the injection of 80mg of methylprednisolone and 1mL

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of 0.5% bupivacaine into the nucleus upon completion of the discectomy. Inpatients with radicular complaints, he injected 40mg of methylprednisolone and1mL of bupivacaine around the offended nerve root. All patients demonstrated acorroborative protruded disc on MRI, CT, or postdiscography CT (68). Bonaldi’sdata suggest that the addition of a corticosteroid and anesthetic does notsignificantly alter the effect of APLD on clinical outcome. However, his patientcohort was not pure and contained patients with both purely axial and radicularpain, thus preventing the assessment of the effect of corticosteroid on clinical signsand symptoms. Yet, his work is the largest investigation of postsurgical patientswith recurrent disc herniation. The 78% success rate in this subgroup approachesfindings in earlier work (66). However, the 9.6% rate of loss to follow-up, shortfollow-up interval, and outcomes measured largely by postal questionnaires wereflaws of the study.

In a prospective, randomized trial, Revel et al. compared APLD tochemonucleolysis in 141 patients with lumbosacral radiculopathy unresponsiveto 30 days of conservative medical treatment (70). Each patient had a corroborativedisc herniation at a single level as detected by MRI, CT, or myelography. Seventy-two patients underwent chemonucleolysis in which 2mL (4000U) of chymopapainwas administered intradiscally into each treated disc. Sixty-nine patients

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FIGURE 5(A) APLD nucleotome device. (B) In contrast to surgical forceps, the side port

allows the reciprocating blade access to the nuclear material. Abbreviation: APLD,automated percutaneous lumbar discectomy.


underwent APLD, but the volume of nuclear tissue removed was not reported.Thirty-two patients did not complete the study and were treated as failures. At sixmonth follow-up, 61% of the chemonucleolysis group and 44% of the APLD groupconsidered the treatment outcome successful. The patient had to consider his orher improvement better than “moderate” to be categorized as a treatment success.In contrast, the investigators judged 77% of the chemonucleolysis group and 83%of the APLD group as successfully treated. At one year post-procedure, 83% of thechemonucleolysis patients and 61% of the APLD patients felt their outcome wassuccessful. The authors did not attribute the low rate of success for APLD to aparticularly low rate of loss to follow-up (3%).

Chatterjee et al. randomized 31 patients to APLD and 40 patients tomicrodiscectomy as treatment for lumbosacral radiculopathy due to a small discprotrusion unresponsive to six weeks of conservative care (71). At six months, 29%of the APLD group, after removal of a mean of 2.1 g of nuclear content, and 80% ofthe microdiscectomy group experienced good or excellent results. Twenty of the 22failed APLD cases elected to undergo microdiscectomy and 13 (65%) achievedgood or excellent results, which is less than the 80% success rate of themicrodiscectomy group. This calculation may underestimate the failure ofmicrodiscectomy in this subgroup of patients if all 22 had undergone surgerywith just 13 successful outcomes, leading to a 59% success rate. Furthermore, the80% success rate observed in the surgical group is less than the 93% success rate ininitial microdiscectomy cases encountered in an independent trial pursued by theinvestigators (64).

Grevitt et al. enrolled 137 patients into a prospective study utilizing Q3VAS,Oswestry Back Disability form, and Short Form 36 as outcome measurement toolsto assess improvement in radicular signs and symptoms after APLD (107). Nopatient improved despite conservative care of physical therapy and epiduralsteroid injections, and the mean duration of preprocedure symptoms was16 months (3–26 months) Q1. Twenty-two patients were lost to follow-up, and17 patients eventually required surgical intervention. At a mean follow-up periodof 55 months, 52% of patients were successfully treated with APLD. If the22 patients lost to follow-up had been successfully treated, successful outcome mayhave been achieved in 64% of patients. Two of the surgical cases had persistentradicular pain due to sequestered disc material at the index level. The majority ofpatients eventually undergoing late surgery were being treated for persistent andprogressive axial lumbar pain. The authors did not report any results of furtherdiagnostic evaluation such as provocative discography or diagnostic facet jointblocks to verify the source of persistent lumbar pain.

After treatment with APLD, most patients will experience mild para-vertebral lumbar muscle spasm or guarding lasting a few days. Rarely are thesespasms severe (65), and they appear to require analgesic medications lessfrequently than after chemonucleolysis (42% vs. 10%) (70) Q1. Discitis occurs with asimilar frequency as in provocative discography, with an observed incidence of0.06% to 0.2% (65,68,106). Rare cases of psoas muscle hematoma have beenreported (65,68). The overall complication rate as observed in large trials hasfallen between 0.06% (106) and 0.95% (68). Permanent injury to neural elements,dura, urinary tract, gastrointestinal system, or major blood vessels is extremelyrare and has not been encountered in large trials (65,66,68,106). However, twoisolated cases of cauda equina injury have been documented as a result of probemisplacement (108,109).

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THERMAL DECOMPRESSION—LASERThe poor performance of APLD compared to conventional open discectomyinterfered with its momentum as a minimally invasive percutaneous decom-pressive technology. In 1986, Choy et al. employed thermal technology to removenuclear contents effectively decompressing the intervertebral disc (110). The term“laser” is an acronym for “light amplification by stimulated emission of radiation”(111). The laser–tissue interaction in biological tissues is determined by the physicalproperties of the laser (wavelength, pulse-length, energy density), and the optical,biomechanical, and biochemical properties (absorption, heat conduction, scatter-ing, reflection) of the targeted tissue. The absorption spectrum of the nucleuspulposus is comparable to other water-containing tissues (111). Therefore, ablatingnuclear tissue by energy absorption is best achieved by utilizing a laser that iswavelength matched to the known absorption bands of water in the visible andinfrared regions (86).

Choy et al. reported their findings after treating 333 patients who hadpersistent radicular symptoms despite three months of conservative care due to acontained lumbosacral disc herniation on MRI or CT (74). Patients demonstratingspondylolisthesis, central or lateral canal stenosis, or advanced disc degenerationwere excluded. At a mean follow-up of 26 months, 78.4% of the 333 patients wereassessed as having good-to-fair results as defined by the Macnab criteria. Theauthors did not differentiate between fair and good responses, which mightrepresent two different clinical outcomes despite being grouped together in thesame category. Although the Macnab criteria for a fair result include no signs ofradiculopathy, patients in this group may be functionally nonproductive and stillrequiring certain medications due to intermittent episodes of mild lumbar orradicular pain. Choy has published his subsequent experiences (75,76) withinhomogeneous patient populations with either radicular or axial pain who wereundergoing treatment at multiple levels, again relying on loosely defined outcomecriteria at long-term follow-up.

McMillan et al. found the short-term improvement of percutaneous laser discdecompression PLDD beneficial, primarily in patients suffering from lumbosacralradicular symptoms rather than axial lumbar pain (77). Each patient underwentPLDD with the Nd:YAG laser in a similar fashion to Choy’s description. Of30 patients with primarily radicular pain at baseline, 24 (80%) demonstratedimprovement, as measured by the American Academy of Orthopedic SurgeonsPain Assessment Questionnaire, and the mean scores improved by 68% betweenbaseline and follow-up. Assessment was completed at follow-up evaluations atthree months, and each patient underwent treatment of one segmental level afterMRI evidence of a corroborative disc herniation with less than 50% reduction indisc height (77). Although flawed by a short follow-up period, McMillan et al.’sstudy utilized an objective measurement tool to document improvement in anendpoint.

Relying on the modified Macnab criteria for assessment, Casper et al. treated222 patients who presented with signs and symptoms of lumbosacral radiculo-pathy (78). Patients who were deemed to be symptomatic due to central or lateralcanal stenosis or disc herniation sequestration were excluded. Each patientunderwent PLDD using holmium:YAG laser with a Sidefire fiber containing a550µm optical fiber (78). Good and excellent results were deemed successful whilefair or poor were unsuccessful. Eighty-four percent of patients were successfullytreated at a follow-up of one year. Of these, 62.5% experienced excellent results and

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37.4% experienced good results. Of the 35 failures, 10 underwent open surgery forsequestered disc fragment, lateral stenosis, or suspected discitis, 12 underwent asecond PLDD at the index level, and 13 experienced fair or poor outcomes.Although the modified Macnab criteria more stringently evaluate postproceduraloutcomes that are impressive, the absence of a control group precludes theconclusion that PLDD was solely responsible for the improvement measured.However the mean duration of preprocedural symptoms was 24.8 months, whichpresumably would have allowed for natural regression toward the mean.

The most common side effect of PLDD is postprocedural paraspinal musclespasm or guarding, which occurs in 10% of cases (84). These symptoms can varyfrom mild stiffness to disabling pain, with the patient listing toward the side oftightness (84). Typically, the lumbar pain dissipates over three to four days andcan be addressed with oral muscle relaxants (84). Infectious and aseptic discitiseach occurs with an incidence of 0.3% per treated disc (76), and in Choy’sexperience, infectious discitis has not occurred since the implementation ofroutine preprocedure intravenous antibiotics (76). Thermal injury of nervoustissue has been observed, with the incidence varying from 0% to 0.8% (76–78)and to as high as 8% in one study (79), and is likely related to incorrect fiberplacement (84). Most cases are transient and resolve over one to five months(78,79), but permanent injury can occur (79). Isolated cases of intestinal injury,sympathetic chain irritation (85), introducer needle heating (84), and dislodge-ment of needle tips have been reported (84). Thermal endplate necrosis has beenreported (69) but has not been encountered by experienced physicians (74–78). Itsoccurrence appears to be operator related and due to rotation of the side-firingprobe in a cephalad and/or caudad direction, thus directing the laser beamtoward an endplate (84).

NONTHERMAL DECOMPRESSION—NUCLEOPLASTYRadiofrequency ablation (RFA) of tissue is the process of applying directedradiofrequency energy to destroy or modify the targeted tissue. RFA has beenapplied to various tissues including tonsillar and pharyngeal tissues (112), cardiacmuscle and nervous tissue (113), and peripheral nerves (114). RFAwas pursued inthe orthopedic arena to shape and remove articular tissue (115). There is anecdotalevidence of more rapid healing of cartilaginous soft tissue with less scarring withRFA when compared to lasers and electrocautery (116). In contrast to its lasercounterpart, RF heating causes less tissue destruction without a similar amount ofinadvertent thermal damage to adjacent tissue. Application Q4of RFA to theintervertebral disc was a logical extension of this new technology.

Nucleoplasty is the percutaneous decompression of an intervertebral disc bythe application of patented Coblation technology, in which RF energy is applied toa conductive medium, causing a focused plasma field to form around theenergized electrodes (Fig. 6). This plasma field contains highly ionized particles ofsufficient energy to cleave organic molecular bonds within tissue, forming achannel (117). The by-products of this nonheat-driven process are the elementarymolecules and low-molecular-weight inert gases, which escape via the introducerneedle (117,118). As the RF probe is withdrawn, the newly created channel isthermally treated, producing a zone of thermal coagulation. Thus, nucleoplastycombines coagulation and tissue ablation to form channels within the nucleus anddecompress an intervertebral disc herniation (119).

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Singh reported improvement in both axial and radicular pain in a smallcohort of patients evaluated postprocedurally at three months (119). However,patients with complaints of either axial lumbar pain or radicular pain wereenrolled in the study. A year later, Sharps and Isaac published their findings againin a cohort of patients with mixed complaints of axial lumbar and radicular lower-limb pain (88). The authors initially enrolled 49 patients and reported a 79%success rate at three months in 41 patients. A successful outcome was defined as agreater than 2-point reduction in VAS score, patient satisfaction, absence of narcoticuse, and return to work. The authors additionally reported a decrease in the meanVAS score of 3.3 points among the 13 patients who were assessed at 12 months afterthe procedure. The authors, however, did not report the narcotic utilization, returnto work, or patient satisfaction data (88). Later in 2002, Singh et al. prospectivelystudied 80 patients with either lumbar or radicular pain (89). Sixty-nine patientswere available for follow-up evaluation at 12 months by either telephone interviewor clinical encounter. Seventy-five percent of these 69 patients reported a reductionin their pain scores that were statistically significant, with 54% of patients reportingrelief of 50% or more. Compared to baseline, nearly half of the patients reportedstatistically significant improvement in their sitting, standing, and walkingcapabilities (89). However, this was an uncontrolled study, and the assessment ofimprovement can only be suggested to be attributable to the intervention, anddifferent diagnostic categories, axial versus radicular, were evaluated similarly.

In the largest clinical trial investigating nucleoplasty in the lumbar spine,Alexandre et al. studied 1390 patients presenting with either axial or radicular paindue to a contained disc herniation demonstrated by advanced imaging studies (90).The symptoms had been ongoing for a minimum of three months despiteappropriate conservative care. At 12 months, 55.8% of the treated patients achievedexcellent (total resolution of symptoms, full return of function) results and 24.9%good (fairly total symptom resolution, good quality of life) results. However, theauthors did not confirm how many subjects were available at follow-up. Noprospective, controlled trials investigating nucleoplasty’s utility in treatingspecifically lumbosacral radiculopathy have been published. A multicenter trialassessing nucleoplasty’s efficacy versus therapeutic SNRIs for lumbar radicularpain due to contained disc herniations is underway.

The most common side effect of lumbar nucleoplasty is localized soreness at theprocedure site; thiswas observed at 24 hours in 48%of 150 patients treated at The PennSpine Center (120). Axial lumbar pain can be a complaint in 5% of patients for up to 10(90) to 14 days (120). Less commonly, at 24 hours, 9% of patients reported new areas ofinconsequential leg pain and 8% new areas of lumbar pain. No permanent neurologic,vascular, or orthopedic injury has been observed (88–93). Intradiscal temperatures

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FIGURE 6Nucleoplasty wand.


exceeding60˚Chavebeenmeasuredwithin3 to4mmof thenucleoplastyprobe tip (91).However, histologic studies have not found gross or microanatomical evidence ofextreme tissuedamage (121,122).Within thenucleus, a small 1.0mmchannel is created,which is surrounded by intact fibrocartilage cells and collagenmatrix. No alteration oftheproteoglycanorcollagenstructure,norendplatedamagehasbeenobservedtooccur(121,122). Furthermore, no damage of the neural elements has been documented(88–93,121,122). If the applicator is maintained at a distance of 3 to 4mm from anycritical structure, unintentional thermal damage may be avoided (91).

MECHANICAL DECOMPRESSION—DEKOMPRESSORIn January 2001, the FDA approved the clinical use of a new 1.5mm percutaneouslumbar discectomy probe, the Dekompressor probe, for the treatment of containedintervertebral disc protrusions (94). The device is a disposable handheldinstrument driven by a battery-powered subminiature DC motor connected toan implant grade precision ground titanium probe with a helical auger as its distaltip (Fig. 7) (123). A 17-gauge outer cannula provides access to the disc via anextrapedicular approach. When activated, the auger tip (Fig. 8) rotates at 12,000rotations per minute, creating localized suction, which removes nuclear materialand aspirates it through the cannula into a collection chamber using anArchimedes’ pump principle (94,95,123). The thixotropic nature of the nucleus,due to which nuclear material becomes less viscous when in motion, provides anideal application for the Archimedes’ pump mechanism employed by theDekompressor probe (123). The helical auger tip is relatively inactive whenengaged in the more fibrous annular tissue (123).

The first human application—the successful treatment of a 36-year-old malesuffering from contained 4.5mm herniation at L4-L5 and 9.5mm herniation atL5-S1— was reported in 2003 in an open forum. Alo et al. then pursued aprospective study of 50 consecutive patients with stringent inclusion and exclusioncriteria (94). Each patient presented with lumbosacral radicular signs andsymptoms of at least a six-month duration due to a corroborative contained disc

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FIGURE 7Handheld Dekompressor device: the black handle contains the battery-powered

motor. Once nuclear material reaches the clear plastic collection chamber, 2 cc of nuclearcontents have been aspirated.


herniation ≤ 6mm in size. Conservative care including physical therapy, oralanalgesic and anti-inflammatory medications, and transforaminal epiduralcorticosteroid and anesthetic injection did not provide lasting relief. Subsequentto these failed therapeutic injections, each patient underwent confirmatorydiagnostic selective nerve root blocks with 0.5 to 1.5 cc of anesthetic; a positiveresponse was defined as a > 80% reduction in the preblock radicular pain level forthe duration of the pharmacologic effect of the anesthetic. Twelve patientsunderwent percutaneous decompression at two levels, and outcomes wereassessed at six months regarding VAS rating, analgesic usage, patient satisfaction,and functional improvement. Patient satisfaction and functional improvementwere assessed subjectively by asking each patient if these parameters hadimproved. During decompression, 0.75 to 2.0 cc of nuclear material was removed.At follow-up, 74% of patients had reduced their analgesic intake, 90% reportedimprovement in their functional status, and 80% reported an overall satisfactionwith their treatment, and the reduction in the mean VAS rating was 60.25%, whichwas significant (p < 0.001). Six patients experienced zero radicular pain at sixmonths. No remark was made regarding surgical intervention of any of thetreatment failures, and objective, validated outcome measurement tools for patientsatisfaction and function were not utilized, and the follow-up interval was short.

In a subsequent study reported by Amoretti et al., 10 patients wereretrospectively reviewed at 6 to 10 months after percutaneous disc decompressionusing the Dekompressor probe (95). Each patient had a history of recalcitrant“sciatica” related to a corroborative contained intervertebral disc herniation onMRI that did not improve despite CT-guided periradicular “infiltration” and anymedical therapy. The authors did not reveal the volume of tissue removed, andthey assessed outcome by VAS ratings and analgesic usage. At a mean follow-up of8.6 months (6–10 months), eight patients (80%) were satisfactorily treated, with adecrease in VAS rating of more than 70% and complete elimination of medicaltherapy. The two failed cases initially experienced improvement, with oneundergoing open discectomy for an extrusion that may have been misinterpretedon initial MRI evaluation, and the second responded to medical treatment. Thiswas a small retrospective study without validated outcome measures other thanVAS ratings that suggests improvements may be stable beyond six months.Although no other clinical trials have been published, our experience in using

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FIGURE 8The helical auger tip of the Dekompressor probe aspirates nuclear contents

without disrupting annular fibers.


Dekompressor to treat lumbar radiculopathy due to contained disc herniationsafter no prolonged benefit from transforaminal epidural steroid injections ortherapeutic SNRIs mirrors the results of Alo et al. and Amoretti et al.

Among the 60 published Dekompressor cases, no complications have beenreported (94,95). Complications were not specifically reported by Alo et al., butAmoretti et al. remarked that no complications were encountered at any point inthe postprocedure period. Nuclear tissue removed in Alo et al.’s study reportedlydid not reveal evidence of tissue injury in any of the samples (94). Direct andintentional operation of the device against annular fibers did not visually affect orremove annular tissue in lamb cadavers (123). In our experience, a minority ofpatients will report localized soreness at the insertion site that eventually resolvesover five to seven days. Equally commonly, patients may experience mild,transient paresthesias in the distribution of the previously affected nerve rootabout seven days after the procedure that eventually resolve over the ensuing 7 to10 days. The first author has encountered one case in which a patient developedsevere radicular pain 24 to 28 hours after the decompressive procedure that wassubsequently abolished within 24 hours of the completion of a transforaminalepidural steroid injection at the index level. Among all the cases published andperformed by ourselves, we are not aware of any infections, vascular injury,viscous injury, or injury of neural elements. Presumably, the risk of infection wouldbe similar to that of discography.

n CLINICAL APPLICATION OF NONENDOSCOPIC PERCUTANEOUSDISC DECOMPRESSION

In the hierarchy of research methodology, randomized, controlled trials areuniversally accepted as providing evidence of the highest grade. In contrast,observational studies have less validity and are predisposed to overestimatingtreatment effects (124). The Agency for Health Care and Policy Research (AHCPR)has utilized a rating schema composed of five levels of evidence to evaluate thestrength of published articles in determining management guidelines. The fivelevels are as follows: level I (conclusive): research-based evidence with multiplerelevant and high-quality scientific studies; level II (strong): research-basedevidence from at least one properly designed randomized, controlled trial ofappropriate size (≥ 60 patients in each arm), and high-quality or multiple adequatescientific studies; level III (moderate): evidence from well-designed trials withoutrandomization, single group pre–post cohort, time series, or matched case–controlstudies; level IV (limited): evidence from well-designed nonexperimental studiesfrom more than one center or research group; and level V (intermediate): opinionsof respected authorities, based on clinical evidence, descriptive studies, or reportsof expert committees.

Level I evidence exists proving both short- and long-term efficacy ofchemonucleolysis in treating lumbosacral radiculopathy due to a contained discherniation (51–54). Level II–III evidence has been generated supporting chemonu-cleolysis as being as effective as open surgical discectomy (56,99). Level IIIevidence has been collected demonstrating that chemonucleolysis is safe, with alower incidence of major complications compared to open surgery (101,102,125).Despite compelling evidence, chemonucleolysis has been abandoned as apercutaneous disc decompression treatment modality because injection of the

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proteolytic enzyme is less controlled and target specific and has led to severe andpersistent lumbar pain. Major complications such as anaphylaxis can be minimizedwith pretreatment and testing, and misplacement of the probe and injection ofchymopapain can be improved with advancement in operator skill and experience.An interesting and perhaps promising intervention is the combination ofchemonucleolysis and mechanical decompression. Endoscopic decompressionafter pretreatment with low-dose chymopapain has yielded impressive results inlarge trials (126,127). Conceptually, this combined intervention is appealing as itallows a more controlled desiccation and cicatrical process, by injection of a lowerchymopapain dose, followed by a quick attrition of these effects by removal of aportion of the proteolyzed nucleus and the proteolytic enzyme. Whether the sameresults can be achieved by nonendoscopic decompression subsequent tochemonucleolysis needs further examination.

By virtue of limited, uncontrolled clinical trials, mechanical decompressionby Dekompressor and Coblation technologies are suggested to be effective by levelIII–IV evidence (88–95). Mechanical decompression with Dekompressor may bebetter supported currently by clinical work that has investigated its utility in well-defined patient populations suffering from lumbosacral radiculopathy due todefined disc herniation who have been confirmed to be unresponsive to selectivespinal injections. However, conclusive evidence is lacking, precluding a definitiveconclusion regarding Dekompressor’s efficacy compared to placebo or opensurgery. The utility of Coblation decompression in the cervical spine may be bettersupported than in the lumbar region (92,93), as trials investigating the efficacy ofCoblation in treating defined cervical radiculopathy have been pursued. Incontrast, less well-defined studies have been engineered in the lumbar spine(88,89). Further investigation via controlled trials are warranted to better define therole of these technologies in percutaneously decompressing disc hernia, becausetheir safety has been well documented (91–94,120).

Percutaneous laser disc decompression and automated percutaneousdiscectomy have been more widely studied due to their maturity but conclusiveevidence is lacking as no controlled trials have been published or presented.Although large, prospective, observational studies have demonstrated success-ful results (65), APLD was less successful at treating radiculopathy thanchemonucleolysis in a well-designed study (70). In a smaller study, opensurgery achieved better results than APLD (71). Hence, level II–III evidenceexists against APLD compared to chemonucleolysis or open surgical discect-omy. Furthermore, observational studies utilizing valid outcome tools havefound disparate results (106,107). Altogether, level III evidence supports APLD,but stronger evidence suggests that APLD is less effective than chemonucleo-lysis. Cervical automated percutaneous decompression data are sparse (68),which precludes a definitive statement regarding the efficacy of this technologyin the cervical spine.

Prospective, observational investigations of PLDD have demonstratedvariable success rates. Most studies have utilized loosely defined criteria ofsuccessful outcome (74–79), and studies using structured outcome tools have ashort follow-up interval (77). Therefore, level III–IVevidence has been generated tosupport PLDD. Cervical laser disc decompression has been employed to treat bothcervical radicular and axial symptomatology (80), with loosely defined outcomemeasures (81,82). Hence, again only level III–IVevidence exists supporting cervicallaser decompression.

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A confounding variable in a cohort of these studies (68) has been thetreatment of disc reherniation at a previously surgerized level. In this scenario, theintervertebral disc is more degenerated than a comparable herniation in a virginspine. Hence, a more fortuitious mechanical debridement may be necessary toachieve clinical success. Automated percutaneous lumbar discectomy has beenmost thoroughly investigated in this patient population, with a success rateapproaching 80% (68). Decompressive efforts with Coblation, laser, and chymo-papain may not be able to effect a more degenerate herniated intervertebral disc.The nuclear substrate in this scenario is more fibrocartilaginous and may be moreresilient to thermal, enzymatic, and nonthermal treatment. Manual decompressionwith the Dekompressor warrants further investigation based on this concept.Currently, APLD appears best suited to alleviate persistent radicular symptomsdue to a reherniation after previous open surgical discectomy.

Nonendoscopic percutaneous disc decompression (NEPDD) with chymopa-pain is effective in treating lumbosacral radiculopathy (51–54). Its safety has beencontested, but new concepts may provide a mechanism by which these rarecomplications are further reduced. NEPDD with other modalities have achievedsuccessful outcomes in 52% to 85% of inspected cases. Despite the methodologicalflaws inherent in someof these audits,NEPDDrepresents aviable,minimally invasiveintervention primarily indicated for treatment of radicular signs and symptoms.

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Caveats of Monitored Anesthesia forPercutaneous Transforaminal EndoscopicSpinal Surgery

3 Alexander Godschalx

n INTRODUCTION

Spinal surgery procedures are increasingly performed in surgery centers and othertypes of outpatient settings. Therefore, advances in local anesthesia, regionalblocks, and conscious sedation techniques have become very attractive to spinalsurgeons. This trend toward increased use of sedation-anesthesia is supported byimproved delivery techniques and newer, short-acting drugs suitable for sedation.Sedation techniques in combination with local or regional anesthesia can improvepatient comfort, safety, and satisfaction during surgery. Close cooperation with theanesthesiologist administering the sedation analgesia is required for adequatesedation and monitoring of patients.

In this chapter,writtenbyananesthesiologist for spinal surgeons, theobjectivesand technical caveats of providing anesthetic care for the patient undergoingtransforaminal endoscopic surgery (TES) are discussed. With the objective ofimproving the understanding of the technical caveats of effective conscioussedation and analgesia for TES, recommendations for intraoperative monitoringand relevant use of adjuvant drugs, such as sedative-hypnotics, anxiolytics, andanalgesics, are reviewed (1).

n DEFINITION

The most commonly accepted definition of sedation-analgesia is from TheAmerican Society of Anesthesiologists (ASA) (2). Q1They have introduced what isknown as monitored anesthesia care (MAC), where anesthesiologists are called onto provide local anesthesia services to a particular patient undergoing a plannedprocedure. The aim of the MAC is to ensure maximum safety of and minimumdiscomfort to the patient undergoing a procedure under local anesthesia, forexample the TES procedure. The policy of the ASA states that the same standard ofcare should be provided by an anesthesia practitioner during MAC as for generalor regional anesthesia (3). The ASA emphasizes the selection of appropriatepatients for sedation, complete medical evaluation, appropriate facilities, equip-ment, dietary precautions, monitoring, documentation, personnel, and a postseda-tion guideline.

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37

n ADVANTAGES

The TES procedure is performed using local anesthesia and adequate analgesia/sedation as defined by the MAC. Q2The ambiance in the operating theatre must besuch that it induces calmness in the patient. No unrelated or recreational talkingshould occur in the operating theatre. The surgeon must be trained in performingprocedures with patients under sedation-anesthesia. Gentle surgical techniquesshould be used, with careful tissue handling. If these are kept in mind, theadvantages for patient and surgeon are numerous when using MAC.

The advantages for the patient and surgeon are listed in Figure 1 andFigure 2.

n SEDATION

One of the primary goals of MAC during the TES procedure is achieving amaximum level of safety, comfort, and satisfaction for the patient. Adequatesedation during local anesthesia is often desirable to diminish anxiety and fearassociated with the operation room (OR) activity and surgical preparation. Studieshave shown that patients prefer surgery under local anesthesia with sedationover local anesthesia only (4). To help relieve the discomfort associated with theTES procedure, a low dose of sedative drugs can be given. The objective is toproduce a level of sedation in which the patient is relaxed and calm, and rationalverbal communication is continuously possible. Administration of sedativedrugs results in a continuum from drowsiness to deep sleep and can progressquickly to unconsciousness or general anesthesia, as is shown in Figure 3(Kaplan) Q3(4).

The level of sedation that is required during the TES procedure is conscioussedation or sedation- analgesia. This is a medically controlled state of depressedconsciousness in which (i) protective reflexes are maintained, (ii) the patient retainsthe ability to independently maintain a patent airway, and (iii) there is anappropriate response to physical stimulation or verbal commands (“open youreyes”) (6).

The objectives of conscious sedation as outlined by Scamman et al. (7) are asfollows:

1. To relieve anxiety and produce amnesia. These goals are accomplished bymeans of good preoperative communication and instruction, low levels of visual

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Reduced patient anxiety (comfort and satisfaction)Less pain on the initial injection of local anestheticReduced deep traction pain during surgeryGreater patient tolerance of long procedures (position on the table)Avoidance of risk associated with general/spinal anesthesiaAmnesia for the surgical or procedural eventMore streamlined recovery room process with faster patient dischargeFewer postoperative complications compared to general/spinal anaesthesia

FIGURE 1Sedation ± analgesia: Advantage for the patient.

38 n Godschalx

and auditory stimuli in the OR, maintenance of patient warmth and covering,and adequate choice of drugs (midazolam).

2. To provide relief from pain. Opioid analgesics are given in order to supplementlocal anesthetics.

3. To achieve adequate sedation with minimal risk. Sedative medication shouldnot interfere with the patient’s ability to communicate verbally, and the usualmonitoring devices and emergency systems must be available.

Patients’ responses to sedative agents vary considerably. It is thereforeimportant that the same monitoring facilities used for safe general anesthesia areapplied to sedation-analgesia. Close contact between the anesthesiologist and thepatient is essential. Acceptably safe sedation is up to and including sedationlevel 3, Q4in which the patient’s eyes are closed but the patient can be roused oncommand (Fig. 4, sedation scale) (8).

n ASSESSMENT

Comprehensive preoperative patient assessment is as important in a patientundergoing MAC during the TES procedure as it is for those undergoing generalanesthesia. A practical streamlined system is outlined in Figure 5.

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Protective reflexes maintainedPatent airwayResponds appropriately

AwakeConscioussedation

orSedation and

analgesia

Deepsedation

Generalanesthesia

Cardiopulmonary arrest

Loss of reflexesUnable to maintain airwayImpaired response

FIGURE 3The spectrum of sedation.

Optimal operating conditions for surgery can be achieved, with improved patient toleranceReduced sympathic response to surgeryOperating time can be reduced with a cooperative patientSurgeon is more at ease with a cooperative patient

FIGURE 2Sedation ± analgesia: Advantage for the surgeon.

Caveats of Monitored Anesthesia n 39

Before surgery, patients should receive written information relating to thesafety aspects of MAC. Instructional videos both on information pertaining to theday of surgery and on sedation choice are also useful. The assessment process canbe streamlined by the use of a health questionnaire, which will facilitate patientassessment.

A fully informed patient who has received a thorough preoperativeexplanation will have less preoperative anxiety on the day of surgery, and it willbring about a better rapport between patient, surgeon, and anesthesiologist. Thiswill also assist the informed consent process.

Preoperative visits should be made by the anesthesiologist responsible for theprocedure. The anesthesiologist must evaluate if the patient is suitable for MAC. Inuncooperative patients, particularly those who have extreme anxiety, significantpsychiatric problems, and severe learning disabilities, sedation can be difficult. It isvery important for the anesthesiologist to see the patient in a more or less normalsituation, to make contact with the patient, and to discover topics for theintraoperative dialogue. It is also important for the patient to get accustomed to theanesthesiologist and to build up a working relationship. We believe that thispreparation enables an optimal medical and psychological interaction with the

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AwakeDrowsyEyes closed but rousable to commandEyes closed but rousable to mild physical stimulatioEyes closed and unrousable to mild physical stimulation

FIGURE 4Sedation scale.

Surgeon:Type of anesthesia raised, discussion with patient as required.

Pre-admission assessment by trained nurse:Assessment of patient’s general healthPlays instructional videos (if available)

Answers patient’s questions

Anesthesist:Provides verbal and written information about MAC

Expectations and anxieties discussedInformed consent

FIGURE 5Streamlined preoperative patient assessment.

40 n Godschalx

patient throughout the procedure. Pasquet introduced the term “vocal anesthesia,”which perfectly describes the importance of a good dialogue setting between theanesthesiologist and the patient (9).

Special attention is given to the following topics during the preoperativevisit: positioning on the side, sedation level, lying still for a longer period,temperature, and the possibility of two or three painful moments during the TESprocedure. Our message to the patient is as follows: we are prepared for almosteverything and are able to handle every kind of discomfort you might experience.If you feel a problem, tell us and we will do our best to solve it, but don’t try to do iton your own!

The anesthesiologist must consider the patient’s needs and choice ofsedation. Discussion with patients about their expectations has been shown toimprove patient satisfaction. The preoperative assessment allows appropriatesedation drugs and techniques to be tailored to the patient’s needs, and patientscan be reassured about any concern they may have. The needs of every patientmust be assessed individually. In Figure 6, the patient’s needs and choices ofsedation are elucidated.

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Suggested questions for patient choice in sedation anesthesia

Patient question

Do you wish to be awake?Do you wish to be drowsy?Do you wish to have no memory of events? (amnesia)Do you want to control your own sedation?Do you want the anesthetist to control your sedation?Do you have any particular concerns or fears relating to your sedation anesthesia?(a) lack of personal control(b) fear of going to sleep(c) fear of pain(d) fear of the unknown(e) fear of seeing the operating room(f) fear of witnessing surgery(g) fear of overhearing conversation related to the surgery

On entering theoperatingtheatre

During localanestheticadministration

Duringsurgery

FIGURE 6Suggested questions for patient choice in sedation anesthesia.


Q5From our experience, it is clear that during the TES procedure, the patientshould be sedated, is calm and not frightened, has a good form of analgesia, and isimmobile when lying on the table. When using techniques and drugs that influencethese parameters, we try to create ideal conditions in the OR so that the patient,while being operated upon, has no fear, is cooperative, obeys verbal commands, ismoderately sedated, has no pain, maintains airway reflexes, and is hemodynami-cally stable.

During the preoperative visit, the anesthesiologist should explain clearly thatthe patient will never be put to sleep during the TES procedure. The patient isobliged to warn the surgeon when feeling pain in the leg. This patient “painfeedback mechanism” gives a clear warning that the surgeon is possibly too closeto the nerve root. When the patient is sedated too much, this “pain feedbackmechanism” is no longer available.

n PROCEDURE

To help achieve the goals of adequate sedation and analgesia during the TESprocedure, we use two drugs, midazolam (benzodiazepine) and remifentanil(opioid). Administration should be individualized to the patient’s level of dis-comfort, as well as to the patient’s drug and medical history. Both drugs are potentand rapid acting and have steep dose–response curves, and thus they should becarefully titrated by variable-rate continuous infusions and/or intermittent bolusdoses (10,11).

Midazolam has properties that make it desirable to use it for MAC duringthe TES procedure. It produces profound perioperative dose-dependentanxiolysis, sedation, and amnesia. It has no active metabolites, permitting rapidpatient recovery. Midazolam can be given both orally and intravenously. Carefultitration to the desired clinical effect will minimize side effects from inadvertentoverdosage. However, there is a wide variation in patient sensitivity tomidazolam (12).

In addition to sedative drugs for anxiolysis and amnesia, supplementalanalgesic opioid agents (remifentanil) are useful in controlling pain during the TESprocedure. Remifentanil decreases back pain secondary to lying in a lateralposition with a pillow in the waist, diminishes the pain at the initial injection oflocal anesthetic, and can help prevent typical painful moments during the TESprocedure. There are two typical moments during the procedure that can beexperienced as painful. The first moment occurs after the placement of the guidingwire when the soft tissue is stretched by the conical tubes. The second painfulmoment is when raising the facet joint.

Remifentanil is the opioid of choice in the TES procedures. It is uniqueamong the opioid analgesics because of its extremely short half-time (three to fiveminutes). Remifentanil is a new opioid in the fentanyl family. Rapid onset andmetabolism make it an easy drug to control for achieving the desired depth ofanesthesia (13). Remifentanil infusions must be carefully titrated to avoid excessiverespiratory depression especially when combined with centrally active drugs suchas midazolam. We often notice when using remifentanil in higher concentrationsthat it has sedative effects that potentiate the action of midazolam. Carefulmanagement of both drugs is necessary to avoid respiratory depression, airwayobstruction, and apnea (14–16).

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42 n Godschalx

The ASA Standards for Basic Intraoperative Monitoring has thereforespecified that the standard for basic monitoring during MAC by the anesthesiol-ogist is the same as for general anesthesia (3). It applies to objective measurementsof the patient’s oxygenation, ventilation, circulation, and body temperature. It alsomakes provisions for “qualified anesthesia personnel” to be present in the room. Itmust be pointed out that monitoring is an extension of the physical examinationand that being in close contact with the patient (feeling the pulse, observingrespiration, watching the operative field, assessing the depth of sedation) is ofgreat importance during the TES procedure.

Q5In addition to improving the safety of MAC, communicating with andtouching the patient (feeling pulse, holding hand) help us to stay in close contactwith the lightly sedated patient. And the patients themselves are the mostimportant sources of feedback when trying to improve the MAC during the TESprocedure.

On the evening before the procedure, a dose of 1.5mg of lorazepam foranxiolysis is given. On the day of surgery, 45 minutes before the start of anesthesia,the patient orally gets 7.5mg of midazolam, and for preemptive analgesia, wechoose a combination of acetaminophen/diclofenac orally. An intravenous line isplaced in the arm opposite to the operation side, and through this line, an antibiotic(cephalosporin) is given. After placing the patient as comfortably as possible in thelateral position on the OR table, the patient is covered in warm blankets. Thepatient is lying in lateral decubitus on the unaffected side on a radiolucent table.The waist should be supported by a small cushion or roll. The patient’s legs shouldbe bent to release lumbar lordosis. The patient’s position is secured with a beltaround the hips. The patient is given a nasal cannula with an oxygen flow rate notbelow 4L/min. After connecting the patient to the monitoring, we start thecontinuous infusion of remifentanil. This infusion should commence at least twominutes before the injection of local anesthetic, which is approximately the onset ofthis opioid. Patients vary in their needs for sedation and amnesia. Some patientswill be comfortable with very light sedation and the role of the anesthesiologistwill be simply to observe and, if feasible, communicate with the patient (this can berecreational). Others will need much deeper sedation, which can be solved bygiving an incremental dose of midazolam. This situation may change during theprocedure and the anesthesiologist needs to titrate drugs according to the changingsurgical stimuli.

The anesthesiologist must also differentiate between pain and anxiety. Painshould be treated by an increasing infusion dose of remifentanil. Anxiety is besttreated with midazolam.

A common pitfall in sedation is to induce a confusional state, when thepatient is a long way along the sedation continuum line. If the anesthesiologistgives additional sedative drugs, this will further contribute to the patient’sdisorientation. Failure to distinguish between the common causes of agitation mayresult in inappropriate therapeutic decisions. The anesthesiologist must haveexperience in sedation techniques to recognize this “risky state.” Failure to do sowill compromise patient care. It is essential to have an experienced anesthesiologistto monitor and maintain safe levels of sedation. He/she should be sensitive topatient requirements and titrate appropriate drugs to reduce anxiety and pain inresponse to surgical events.

As has been stated before, during the TES procedure, there are two specificpainful surgical moments: the dilatation of the soft tissue and the raising of the

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facet joint. The anesthesiologist has to follow the operation closely to anticipatethese painful moments. As stated before, the onset time of remifentanil is twominutes; therefore, it is useless to raise the pump rate the moment the patientexperiences pain: it should have been done “the onset time” earlier. Close contactbetween surgeon and anesthesiologist is as important in MAC as in generalanesthesia.

In Figure 7, the dosage of remifentanil is shown in relation to the differentsurgical stages during the TES procedure. These doses are not rigid, but subject topatient’s needs.

The level of sedation should not be deeper than 4 on the sedation scale (eyesclosed but rousable to mild physical stimulation). During the whole surgicalprocedure, the patient should be able to notify the surgeon if any pain in the leg isfelt. Q5The TES procedure has a low rate of complication probably because the patientwill advise immediately if the surgeon gets too close to the nerve root. This “safetyfeedback mechanism” has to be present during the complete procedure. This is animportant reason why close monitoring of the level of sedation is of greatimportance and should never be below 4 on the sedation scale. This means closeverbal and visible contact between anesthesiologist and patient (Fig. 8).

n POSTOPERATIVE COURSE

One of the principal aims in the recovery room monitoring is to asses the residualeffects of drugs administered intraoperatively and to determine when the patient isfit to be discharged. Recovery facilities and discharge criteria are the same as forgeneral anesthesia, but patients may satisfy these criteria much faster with MACand the TES procedure (17). The low incidence of postoperative pain after the TESprocedure requires no large-scale analgesic therapy. We have noticed two minorpostoperative side effects when using remifentanil for analgesia during the TESprocedure: postanesthetic shivering and nausea and vomiting. Shivering after theTES procedure mostly lasts no longer than half a hour and can be treated with alow dose of pethidine. Nausea and vomiting are relatively common side effects ofopioids and can successfully be treated by antiemetics.

The recovery period after a TES procedure is approximately 1.5 hours. Mostpatients have stable vital signs and are alert and fulfill the recommended dischargecriteria and can go home. Discharge of the patient is authorized by theanesthesiologist and surgeon. The patient must be transferred to the care of a

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Stage 1: IncisionStage 2: Local injectionStage 3: The dilatation of the soft tissueStage 4: Fraising of the facet jointStage 5: Removing the herniaStage 6: Closing

0.1 µg/kg/min0.2 µg/kg/min0.3 µg/kg/min0.3 µg/kg/min0.1 µg/kg/min0.0 µg/kg/min

FIGURE 7Dose of remifentanil in relation to TES surgical stages.

44 n Godschalx

responsible adult to whom written and verbal instructions should be given. This isimportant because in spite of the patient’s apparent alertness, amnesic drugs suchas midazolam may prevent patients from remembering instructions on discharge.

n DIFFICULT PATIENT GROUPS

Particular care should be taken when administering MAC in the following cases.The elderly patient: Respiratory depression can sometimes occur when using

MAC for a TES procedure. This risk is increased by a combination of sedative andanalgesic drugs. The potential for compromising the respiratory system resultsfrom depression of esophageal and laryngeal reflexes, upper airway obstruction,and depression of central hypercarbic and hypoxic ventilatory responses. Theseadverse drug reactions can be minimized by slow administration, careful titration,and assessing the effect before supplementing the dose of drugs. Closecommunication and careful monitoring are required (18).

The sleep apneic patient: Obstructive sleep apnea is a common condition. Thisis made worse when sedative drugs are administered. The anesthesiologist mustbe aware that early airway obstruction can occur before a deeper level of sedationis achieved and vigilant monitoring is required. If the patient has a personal nasalcontinuous positive airway pressure mask, this should be brought to on the day ofsurgery and used perioperatively (19).

A survey by the Federated Ambulatory Surgery Association found higheroverall complication rates after ambulatory surgery with combined local

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FIGURE 8Close contact (visual and verbal) between anesthesiologist and patient during

the surgical procedure.


anesthesia and intravenous sedation (1:106) compared to general (1:120), regional(1:277), and local anesthesia alone (1:268) (20). The poor safety profile attributed tosedation is largely due to people without anesthetic skills administering sedation.If sedation is given by a skilled anesthesiologist and titrated to maintain safesedation levels, and if there is vigilant monitoring, morbidity should be minimal.

n SUMMARY

MAC has become the anesthetic procedure of choice for the TES procedure. Theadministration of sedative and analgesic drugs to enhance patient comfort requirescareful titration and adequate monitoring to achieve the desired goal withoutcompromising patient safety. The effective use of an MAC technique can providehighly acceptable patient comfort while optimizing intraoperative conditions.Patient cooperation, effective local anesthesia, and gentle surgical technique are allessential elements for the successful application of MAC during the TES procedure.

Vigilant monitoring, use of supplemental oxygen, and availability of resus-citation equipment are all essential elements for the safe practice of MAC.

Furthermore, the overall cost of theMAC technique during the TES procedureis less than those of either general or regional anesthesia, thus contributing to thecost effectiveness of the TES procedure and hence to the popularity of this new typeof TES (21,22).

n REFERENCES

1. Sa Rego MM, Watcha MF, White PF. The changing role of monitored anesthesia care inthe ambulatory setting. Anesth Analg 1997; 85:1020.

2. American Society of Anesthesiologists (ASA). Position on Monitored Anesthesia Care.Directory of Members. Park Ridge, IL: American Society of Anesthesiologist, 1997,p. 413.

3. Q6American Society of Anesthesiologists (ASA). Standard for Basic Anesthetic monitor-ing. Directory of Members. Park Ridge, IL: American Society of Anesthesiologists, 1997,p. 394.

4. Lundgren S, Rosenquist JB. Amnesia, pain experience, and patient satisfaction aftersedation with intravenous diazepam. J Oral Maxillofac Surg 1984; 42:646.

5. Q7Guidelines for monitoring and management of pediatric patients during and aftersedation for diagnostic and therapeutic procedures. Pediatrics 1992; 89:1110–14.

6. Q8Practice guidelines for sedation and analgesia by non-anesthesiologist. Anesthesiology1996; 84:459–71.

7. Scamman FL, Klein SL, Choi WW. Conscious sedation for procedures under local ortopical anesthesia. Ann Otol Rhinol Laryngol 1985; 94:21.

8. Mackenzie N, Grant IS. Propofol for intravenous sedation. Anaesthesia 1987; 42:3–6.9. Pasquet A. Combined regional and general anesthesia for craniotomy and cortical

exploration. Part II: anesthetic consideration. Reprint of a lecture given 1953. InternAnesthesiol Clin 1986; 24:1–11.

10. White PF, Vasconez LO, Mathes SA, et al. Comparison of midazolam and diazepam f orsedation during plastic surgery. J Plast Reconstr Surg 1988; 81:703.

11. Egan TD, Lemmens HJ, Fiset P, et al. The pharmacokinetics of the new short-actingopioid remifentanil (g187085B) in healthy adult male volunteers. Anesthesiology 1993;79:881.

12. Dundee JW, Wilson DB. Amnesic action of midazolam. Anaesthesia 1980; 35:459.13. Rosow C. Remifentanil: a unique opioid analgesic. Anesthesiology 1993; 79:875.

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14. Bailey PL, Pace NL, Ashburn MA, et al. Frequent hypoxemia and apnea after sedationwith midazolam and fentanyl. Anesthesiology 1990; 3:826–30.

15. Westmoreland CL, Hoke JF, Sebel PS, et al. Pharmacokinetics of remifentanil and itsmajor metabolite in patients undergoing elective inpatient surgery. Anesthesiology1993; 79:893–903.

16. Gold MI, Watkins WD, Sung YF, et al. Remifentanil versus remifentanil/midazolam forambulatory surgery during monitored anesthesia care [clinical investigation].Anesthesiology 1997; 87(1):51–7.

17. White PF. What is new in ambulatory anesthesia techniques? Ann Refresh Course Lect1997; 411:1.

18. Solomon SA, Kajla VK, Banerjee AK. Can the elderly tolerate endoscopy withoutsedation? J R Coll Phys Lond 1994; 28:407–10.

19. Davies RJ, Stradling JR. Acute effects of obstructive sleep apnoea. Br J Anaesth 1993; 71:725–9.

20. Federated Ambulatory Anesthesia Association (FASA). Special study I, Number 520,1986.

21. Watcha MF. Cost minimization, cost-benefit and cost-utility analyses. In: White PF, ed.Ambulatory Anesthesia and Surgery. London: WB Saunders, 1997, p. 648.

22. Birch BRP, Anson KM, Miller RA. Sedoanalgesia in urology: a safe, cost-effectivealternative to general anesthesia. A review of 1020 cases. Br J Urol 1990; 66:342–5.

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Lumbar Posterolateral (Transforaminal)Selective Endoscopic Discectomy:The Yess Technique

4 Christopher A. Yeung, Victor M. Hayes,Farhan N. Siddiqi, and Anthony T. Yeung

n INTRODUCTION

The open posterior approach to the lumbar spine is the current gold standard foraccessing and removing herniated discs and decompressing the spinal canal.However, the posterior (transcanal) approach has an inherent morbidity andapproach-related limitations with regard to accessing the disc space. This midlineapproach requires significant muscle and ligament stripping, prolonged muscleretraction, partial facet and lamina resection, both nerve root and dural retraction,which promote epidural scarring, and regional or general anesthesia.

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Christopher A. Yeung, Victor M. Hayes, Farhan N. Siddiqi, and Anthony T. Yeung, are all at theDesert Institute for Spine Care, Phoenix, Arizona, U.S.A.

TABLE 1

Lumbar Endoscopic Posterolateral (Transforaminal) Approach: Key Starting Points

The patient is positioned to obtain true anteroposterior and lateral views prior to needleplacement; this will avoid radiographic parallax error and malpositioning of the needle, cannula,and endoscope.The initial needle trajectory and placement is crucial because it will ultimately determine theendoscopic field of view. The optimum needle position is determined based on the pathology orregion being addressed (Fig. 1). The bony constraints of the iliac crest and foramen (facets andlateral vertebral body) will restrict needle and scope trajectory especially at L5-S1; therefore,perfect trajectory and placement is crucial.Use fluoroscopy to confirm instrument location if there is any uncertainty about anatomy orlocation during surgery.Start the endoscopy using the “inside-out” Yeung endoscopic spine surgery (YESS) technique(Fig. 4) (6), accessing the intervertebral disc first, which is always safe! This technique isespecially important during the initial learning curve. Beginning the endoscopy before reachingthe disc annulus can make recognition of foraminal anatomy more difficult and can increase thelikelihood of nerve root injury, except in special situations where the patient’s anatomy and/or thepathoanatomy justify an alternate technique. Examples of specific situations that require an“outside-in” technique are removal of the lateral facet to get into the L5-S1 or a large far-lateraldisc sitting on the exiting nerve root and pushing it into the foramen.It is recommended that the patient be awake and alert until the endoscope is within the discspace to avoid nerve injury. Avoiding excessive sedation prior to this point in the procedure iscrucial, especially during needle insertion, and dilator and cannula passage. We recommendagainst the use of a general anesthetic such as propofol.

49

Although minimally invasive posterior techniques can have smaller incisionsutilizing dilators and tubular retractors that reduce muscle retraction, they stillrequire the same amount of bone resection and dural retraction to expose the discor pathology safely. Hence, even minimally invasive posterior approaches do notremove the morbidity associated with bony resection (i.e., instability) or nerve rootretraction (i.e., neuropraxia), nor do they avoid epidural scarring, which can makerevision surgery difficult. The morbidity and limitations associated with openposterior approaches have motivated surgeons to develop alternative approachesand treatments for disc pathology.

The least invasive of all posterolateral intradiscal techniques is the injectionof chymopapain, a treatment option validated by at least two large prospective,randomized, double-blind studies and numerous cohort studies (1,2). The clinicaluse of chymopapain was widespread in the 1970s, but lost popularity after a fewreports of complications as severe as anaphylactic shock and transverse myelitis(3). These complications may have had more to do with the improper placement ofthe injection rather than the drug itself. Regardless, the manufacturer haltedproduction of the drug, and it is currently not available for use in the United States.There are efforts to bring it back for clinical use however.

The concept of indirect decompression of the spinal canal via a posterolateral,extracanal approach was introduced by Q1Kambin in 1973 using a Craig cannulafor limited nucleotomy in combination with a transcanal approach (4). In 1975,

Q2Hijikata reported the first stand-alone nonvisualized posterolateral percutaneouscentral nucleotomy (5).

Kambin went on to describe the safe triangular working zone (Kambin’striangle) (Fig. 1) and results of arthroscopic microdiscectomy, in which arthroscopic

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FIGURE 1Kambin’s triangular working zone is the site of surgical access for posterolateral

endoscopic discectomy. It is defined as a right triangle over the dorsolateral disc. Thehypotenuse is the exiting nerve root, the base (width) is the superior border of the caudalvertebra, and the height is the dura/traversing nerve root.

50 n Yeung et al.

visualization of the herniation via the posterolateral approach was used for dis-cectomy of contained herniations (4,6–11).

Yeung introduced a unique rigid rod-lens spinal endoscope with anintegrated working channel in 1998 for even more flexibility in accessing the disc,traversing and exiting nerve roots, and epidural space. The endoscope configura-tion offers significant visual improvement and the complementary instrumentsystem improves the ability to perform a true endoscopically visualizeddiscectomy for more than just contained herniations. The specialized slotted andbevel-ended tubular access cannulas enlarged the available working area andallow for same-field viewing of the intradiscal space, annular wall, and epiduralspace. This design allows for improved access to the posterior disc for visualizedfragmentectomy, improved access to the undersurface of the superior articularfacet for foraminal decompression (foraminoplasty), and protection of the neuralstructures by rotating the cannula (12,13).

Yeung expanded on the principles pioneered by Kambin and developed theYeung endoscopic spine surgery (YESS) technique to address intradiscal andforaminal pathology (12–15). This technique uses an “inside-out” protocol, firstsafely accessing the disc, then selectively removing disc tissue from the base of theherniation, and pulling the extruded nucleus back within the disc and out via thecannula. Then the cannula can be manipulated to access the epidural space, lateralfacets, and foramen, and inspect the traversing and exiting nerve roots.

For most spine surgeons, the transforaminal approach is unfamiliar. Accessto this region through an open posterior approach requires significant dissection,bony resection, and soft tissue retraction (usually via a TLIF Q3approach), while stilllimiting visualization of lateral foraminal anatomy (the lateral Q4SAP), frequentlyimplicated in failed back-surgery syndrome. Technological advances and newinstruments have now expanded the scope of pathology that can be addressedusing a transforaminal endoscopic approach in the lumbar spine. This chapter willdescribe the YESS technique and its use to safely access the lumbar spine via anendoscopic transforaminal approach. We will also discuss the indications for,benefits of, and pitfalls in using this approach to access the disc, foramen, andspinal canal.

n BACKGROUND OF SCIENTIFIC TESTING

Current peer-reviewed literature on outcomes of endoscopic transforaminal spinalprocedures are available for discogenic pain from annular tears, discitis, lumbardisc herniations, recurrent lumbar disc herniations, central and lateral spinalstenosis, and failed back surgery syndrome (14–18). Surgical outcomes ofposterolateral endoscopic discectomy for contained lumbar disc herniations arecomparable with those for traditional open transcanal microdiscectomy(6,14,15,18), but with lower surgical morbidity and faster recovery time.

There are two prospective randomized studies comparing transforaminalendoscopic discectomy to posterior microdiscectomy. Hermantin et al. reportedsatisfactory results from video-assisted arthroscopic microdiscectomy in 97% ofpatients compared to 93% in traditional microdiscectomy with an average of31 months follow-up (6). The arthroscopic group had less narcotic use and less timeoff from work. There were 30 subjects in each group. Mayer and Brock also showedpromising results in a prospective randomized study comparing percutaneous

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Lumbar Posterolateral (Transforaminal) Selective Endoscopic Discectomy n 51

discectomy with microscopic discectomy for contained or slight subligamentousherniations (18). The percutaneous group showed comparable or superior results.Long-term disability, defined by return to work status, produced statisticallysignificant differences. In the percutaneous group, 95% returned to their previousoccupation compared to 72.2% in the microdiscectomy group. Each group had20 subjects.

n INDICATIONS/CONTRAINDICATIONS

Current indications for the use of an endoscopic posterolateral approach to thelumbar spine include foraminal and far-lateral disc herniations, contained centraland paracentral disc herniations (19), small nonsequestered extruded discherniations, recurrent herniations, symptomatic annular tears, synovial cysts,biopsy and debridement of discitis, decompression of foraminal stenosis with orwithout spondylolisthesis, visualized total nuclectomy (prior to nucleus replace-ment), visualized discectomy, and endplate preparation prior to interbody fusionor total disc replacement implantation.

Perhaps the ideal lesions for posterolateral selective endoscopic discectomyare the foraminal and extraforaminal disc herniations. The cannula inserts directlyat the herniation site and the exiting nerve is routinely visualized and protected.This approach requires less manipulation of the exiting nerve root than theparamedian posterior approach.

Any herniation contiguous with the disc space not sequestered and migratedis amenable to endoscopic disc excision if the bony anatomy permits anunobstructed approach. This utilizes an “inside-out” technique, where theherniation is grasped from its base within the disc space, pulled back into theworking intradiscal cavity, and removed via the cannula. The size and types ofherniations chosen by the surgeon for endoscopic excision will depend on the skilland experience of the surgeon. Certainly, all contained disc herniations areappropriate for endoscopic decompression. With experience, extruded herniationscan be routinely addressed. This approach is especially attractive for recurrentherniations after a traditional posterior approach since the surgeon can avoid thescar tissue from the previous surgery.

The posterolateral endoscopic approach requires only tissue dilation toaccommodate a 7mm working cannula. Q5This tissue-sparing approach provides forearlier surgical timing when approach-related risk/benefit ratios are factored inafter patients fail conservative treatment and continue to have debilitating painwithout neurologic deficit. Quality-of-life issues and functional issues associatedwith chronic discogenic pain can be addressed with this minimally invasivesurgical option. Therefore, small disc herniations with predominant leg pain,central disc herniations with predominant back pain, Q6IDD, and annular tearscausing chemical sciatica are amenable to disc surgery by endoscopic means.

The discectomy decompresses the disc, alleviating pressure on the annulus,and removes any unstable degenerated disc fragments that could herniate further.Radiofrequency energy can be applied to the annular tears under directvisualization to contract the collagen and ablate ingrown granulation tissue,neoangiogenesis, and sensitized nociceptors. Frequently, interpositional nucleartissue is seen within the fibers of the annular tear preventing the tear from healing.This tissue can then be removed to allow the tear to heal.

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52 n Yeung et al.

Endoscopic foraminoplasty (foraminal decompression) can be readilyachieved with bone trephines/rasps, the side-firing holmium–YAG laser, andendoscopic high-speed drills (20). The roof of the foramen is formed by theundersurface of the superior articular facet. This is easily visualized and accessedvia the endoscope and the previously mentioned tools are utilized to remove boneand enlarge the foraminal opening. Studies by Osman et al. have demonstratedthat decompression through the foramen can be more effective than posteriordecompression for foraminal stenosis. The removal of the posterior one-third of themedial facet produces more instability than posterolateral foraminal decompres-sion (21). Synovial cysts can also be visualized and removed.

In cases of discitis, the posterolateral endoscopic approach will provide arobust biopsy for culture diagnosis, and the infected/necrotic disc tissue can bethoroughly debrided to reduce the bacterial load and accelerate healing (22).Surgeons are often hesitant to perform open debridement in the absence ofneurologic deficits due to the morbidity of the open approach, creation of deadspace and devascularized tissue, and the risk of the infection spreading in thespinal canal. Since only tissue dilation is used, no dead space is created that wouldallow the infection to spread.

Since the technique utilizes local anesthesia with mild sedation, patients withthe afore-stated pathologywho are considered “too high risk” for general anesthesiacan receive treatment safely via this approach and are excellent candidates.

Contraindications include any pathology not accessible from the poster-olateral endoscopic approach. This may include some extruded sequestered discherniations, extruded migrated disc herniations (migrated > 20% of vertebral bodysuperiorly or inferiorly), recurrent or virgin disc herniations with associatedepidural scarring, moderate-severe central canal stenosis, and hard calcifiedherniations. Q7These contraindications are relative, being dependent on the surgeon’stechnical experience and comfort level. More experienced endoscopic surgeons cangain greater access to the pathology by utilizing advanced techniques for boneremoval of osteophytes, stenosis, and the posterolateral corner of the vertebralbody prior to addressing the pathology. Other relative contraindications includeinadequate support staff or equipment to successfully perform the procedure anduncooperative patients.

n SURGICAL EQUIPMENT

The endoscopic posterolateral (transforaminal) approach to the spine is bestaccomplished by using a specially designed endoscope and instruments. There area couple of competing endoscopic systems available, but the most widely used andthe authors’ preferred system is the YESS system from Richard Wolfe MedicalInstruments (Vernon Hills, IL, U.S.A.) (Fig. 2). The current outer diameter of thecannula is 7mm, which is well within the dimensional constraints of foraminalanatomy (Fig. 5). The rigid endoscope houses a 3.1mm working channel (which iscapable of accepting specialized instruments), an irrigation channel, a light source,and a video camera. Specialized instruments include straight and hinged pituitaryrongeurs, straight and flexible suction-irrigation shavers for mechanical tissueremoval, a flexible bipolar radiofrequency probe ( Q8Ellman International trigger-flexbipolar probe) for hemostasis, tissue modulation, and manual probing, and a side-firing holmium–YAG laser (Trimedyne) for precise tissue and bony ablation.

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A standard arthroscopic tower and monitor are also required to visualize theendoscopy. Equipment for capturing video and still pictures is optional.

n STEP-BY-STEP OPERATIVE TECHNIQUE (TABLE 1)

PATIENT POSITIONINGThe patient is made to lie prone on a hyperkyphotic frame with a radiolucent table.The endoscope should be on one side of the patient and the fluoroscopic unit onthe opposite side (Fig. 3).

ANESTHESIAAlthough some experienced international endoscopic surgeons prefer generalanesthesia, the authors recommend mild sedation and local anesthesia so that thepatient is awake and responsive throughout the procedure. The patient can thenprovide real-time feedback in case of nerve irritation from instrument pressureor retraction, adding a layer of safety and allowing the surgeon to adjustthe instruments accordingly. Q9We utilize versed and fentanyl for sedation andrecommend against using general anesthetics such as propofol, which can producetemporary total analgesia, eliminating the patient’s responsiveness to any nervestimuli. The skin, needle tract, and annulus are anesthetized with 0.5% lidocaine.This allows anesthesia without motor block of the nerve roots.

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FIGURE 2Partial instrument set for the Richard Wolf YESS system.

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PROTOCOL FOR DETERMINING OPTIMAL NEEDLE INSERTION SITEOptimal needle placement is the most crucial step of the procedure and is based on the typeof pathology being addressed (Fig. 4). Utilizing a thin metal rod as a radio-opaquemarker and ruler, lines are drawn on the skin to mark surface topography forguidance using biplane c-arm needle placement. These surface markings helpidentify three key landmarks for needle placement: the anatomic disc center, theannular foraminal window (centered within the medial and lateral borders of thepedicles), and the skin window (needle entry point).

n Utilizing a metal rod as a radio-opaque marker and ruler, draw a longitudinalline over the spinous processes to mark the midline on the posteroanterior view.

n Draw a transverse line bisecting the targeted disc space to mark the transversedisc plane on the posteroanterior view. The intersection of these two lines marksthe anatomic disc center.

n On the lateral view, draw the disc inclination plane from the lateral disc center tothe posterior skin. This line should bisect the disc and be parallel to theendplates. This line determines the cephalad/caudal position of the needle entrypoint. When drawing this disc inclination line, the tip of the metal rod should beat the lateral anatomic disc center. The distance from the rod tip to the plane ofthe posterior skin is measured by grasping the rod at the point where theposterior skin plane intersects it.

n This distance is then measured on the posterior skin from the midline along thetransverse plane line.

n At the lateral extent of this measurement, a line parallel to the midline is drawnto intersect the disc inclination plane line. This intersection marks the skin entrypoint or skin window for the needle.

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FIGURE 3Proper operating room set-up.


n The skin window’s lateral location from the midline determines the trajectoryangle into the foraminal annular window. A 45� needle trajectory to the discshould place the needle tip in the true anatomic disc center. If you are attemptingto access the posterior one-third of the disc (which is the typical case), then theoptimum skin window is more lateral (1–2 cm) and the needle trajectory angle is

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FIGURE 4A–F Protocol for optimal needle placement. (A) PA fluoroscopic view enables

topographic location of the midline and the transverse disc plane. The intersection of theselines is the PA anatomic disc center. (B) Lateral fluoroscopic view enables topographiclocation of the disc inclination plane. (C) The inclination plane of each target disc is drawnon the skin from the lateral disc center. (D) The distance from the lateral disc center to theposterior skin plane is measured along the inclination plane. (E,F) This same distance ismeasured from the midline along the transverse disc plane for each target disc. At the endof this measure, a line parallel to the midline is drawn to intersect the disc inclination line.This is the skin entry point or “skin window” for the needle. Abbreviation: PA,posteroanterior.

56 n Yeung et al.

less acute (25–30� in the coronal place). This lateral insertion point should belocated where the skin surface is transitioning from a horizontal surface to avertical surface.

n Alternatively, one can place the rod tip at the anterior portion of the disc whenmeasuring the disc inclination plane. This produces a longer measurement to theposterior skin plane, thus placing the skin window more lateral. This is actuallythe preferred method. This coordinate system of finding the optimal anatomicallandmarks for instrument placement will help decrease the steep learning curvefor needle placement and eliminate the less accurate “down the tunnel” methodfavored by radiologists and pain management physicians.

n The positive disc inclination plane of the L5-S1 disc is noteworthy. A steeppositive inclination line (lordosis) will position the optimal skin window morecephalad from the transverse plane line, avoiding the “high iliac crest.” Aflatly inclined L5-S1 disc will position the optimal skin window with the iliaccrest, obstructing the trajectory of the needle. The skin window will have tostart more medial to avoid the iliac crest, and sometimes the lateral one-quarter of the facet joint must be resected to allow for posterior needleplacement in the disc.

n The first neutrally aligned vertical disc inclination plane is usually at L4-L5 orL3-L4. A neutrally aligned disc inclination plane is in the same plane as thetransverse plane line, and thus the skin window is in line with the transverseplane line. A negatively inclined disc, often at L1-L2 and L2-L3, places the skinwindow caudal to the transverse plane line.

NEEDLE PLACEMENTOnce the starting point and needle trajectory is determined, the skin window andsubcutaneous tissue is infiltrated with 0.5% lidocaine. A 6-inch long, 18-gaugeneedle is then inserted from the skin window at the desired trajectory (coronalplane) and passed anteromedially toward the anatomic disc center. Infiltrating theneedle tract with 0.5% lidocaine as you are advancing the needle will anesthetizethe tissue tract, avoiding pain when the dilator is passed later in the procedure. Tiltthe c-arm beam parallel to the disc inclination plane (the Ferguson view) whileadvancing the needle toward the disc to avoid parallax error. At the first bonyresistance or before the needle tip is advanced medial to the pedicle; turn the c-armto the lateral projection. Avoid advancing the needle tip medial to the pedicleduring the initial approach, because doing so risks inadvertent traversing nerveroot and dural puncture.

Most frequently (and ideally), the first bony resistance encountered is thelateral facet. Increase the trajectory angle to aim ventral to the facet and continuethe approach toward the foraminal annular window. Turning the needle bevel toface dorsal helps the needle tip skive off the undersurface of the facet, but if theneedle then deflects too much, reversing the bevel may allow the needle tofenestrate the ventral facet capsule and hug the bony facet when the exiting spinalnerve is irritated in the course of needle placement. If the trajectory is less thanideal when visualizing the trajectory angle, the skin window can be adjusted toapproximate the ideal trajectory angle. The c-arm lateral projection should confirmthe needle tip’s correct annular location. In the lateral view, the correct needle tipposition should be just touching the posterior annulus surface. In the poster-oanterior view, the needle tip should be centered in the foraminal annular window.

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The above two views of the c-arm confirm that the needle tip has engaged the safezone, the center of the foraminal annular window.

While monitoring the posteroanterior view, advance the needle tip throughthe annulus to the midline (anatomic disc center). Then check the lateral view. Ifthe needle tip is in the center of the disc on the lateral view, you have a centralneedle placement, which is good for a central nucleotomy. Ideally the needle tipwill be in the posterior one-third of the disc, indicating posterior needle placementif you are attempting to access herniations.

EVOCATIVE CHROMODISCOGRAPHYPerform confirmatory contrast discography at this time. The following contrastmixture is used: 9 cc of Isovue 300 with 1 cc of indigo carmine dye. Thiscombination of contrast ratio gives readily visible radio-opacity on the discographyimages, and intraoperative light-blue chromatization of pathologic nucleus andannular fissures, which help guide the targeted fragmentectomy.

INSTRUMENT PLACEMENTInsert a long, thin guide wire through the 18-gauge needle channel. Advance theguide wire tip 1 to 2 cm deep into the annulus, and then remove the needle. Slidethe bluntly tapered tissue-dilating obturator over the guide wire until the tip of theobturator is firmly engaged in the annular window. An eccentric parallel channelin the obturator allows for four-quadrant annular infiltration using small,incremental volumes of 0.5% lidocaine in each quadrant, enough to anesthetizethe annulus, but not the nerves. Hold the obturator firmly against the annularwindow surface and remove the guide wire.

The next step is the through-and-through fenestration of the annular windowby advancing the bluntly tapered obturator with a mallet. Annular fenestration isthe most painful step of the entire procedure. Advise the anesthesiologist toheighten the sedation level just prior to annular fenestration. Advance theobturator tip deep into the annulus and confirm on the c-arm views. Now slide thebeveled access cannula over the obturator toward the disc. Advance the cannulauntil the beveled tip is deep in the annular window, with the beveled openingfacing dorsally. Remove the obturator and insert the endoscope to get a view of thedisc nucleus and annulus. The subsequent steps depend on the goal of theprocedure and pathology being addressed. The basic endoscopic method to excisea noncontained paramedian extruded lumbar herniated disc via a uniportaltechnique is described here. Different steps are utilized for other pathologies andare beyond the scope of this chapter.

PERFORMING THE DISCECTOMYFirst, enlarge the annulotomy medially to the base of the herniation with a cuttingforceps. The side-firing holmium–YAG laser can also be utilized to enlarge andwiden the annulotomy. This is performed to release the annular fibers at theherniation site that may pinch off or prevent the extruded portion of the herniationfrom being extracted. Directly under the herniation apex, a large amount of blue-stained nucleus is usually present, which is likened to the submerged portionof an iceberg. The nucleus here represents migrated and unstable nucleus.

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The endoscopic rongeurs are used to extract the blue-stained nucleus pulposusunder direct visualization (Fig. 5). The larger straight and hinged rongeurs areused directly through the cannula after the endoscope is removed. Q10Fluoroscopyand the surgeon’s instinct guide this step. By grabbing the base of the herniatedfragment, one can usually extract the extruded portion of the herniation. Initialmedialization and widening of the annulotomy reduce the prospect of breaking offthe herniated nucleus and retaining the apex of the herniation in the spinal canal.The traversing nerve root is readily visualized after removal of the extrudedherniation.

Next, perform a minimal bulk decompression by using a straight and flexiblesuction-irrigation shaver (Endius MDS). This step requires shaver-head c-armlocalization before power is activated to avoid nerve/dura injury and anteriorannular penetration. The cavity thus created is called the working cavity. Thedebulking process serves two functions. First, it decompresses the disc, reducingthe risk of further acute herniation. Second, it removes the unstable nucleusmaterial to prevent future reherniation.

Inspect the working cavity. If noncontained extruded disc fragments are stillpresent—by finding blue stained nucleus material posteriorly—then thesefragments are teased into the working cavity with the endoscopic rongeurs andthe flexible radio-frequency trigger-flex bipolar probe (Ellman) and removed.Creation of the working cavity allows the herniated disc tissue to follow the path ofleast resistance into the cavity. The flexible radio-frequency bipolar probe is usedto contract and thicken the annular collagen at the herniation site. It is also used forhemostasis throughout the case.

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FIGURE 5Uniportal technique for selective endoscopic discectomy. Rongeurs are used for

visualized fragmentectomy. The beveled cannula can be positioned to view the intradiscalcavity, annular wall, and epidural space in the same field of vision.


The vast majority of herniations can be treated via the uniportal technique.Sometimes, for large central herniations, the disc needs to be approached from bothsides, a biportal technique. This allows the use of larger articulating instrumentsthat fit through the contralateral 7mm access cannula under direct endoscopicvision.

n POSTOPERATIVE CARE

Since it is recommended that this technique be performed under local anesthesia,most procedures that use the approach can be performed as an outpatientprocedure, with same-day patient discharge. Most patients require only a briefpostoperative monitoring depending on the amount of sedation given. Thepostoperative restrictions are dependent on the pathology being addressed. Smallannulotomies are made during the scope insertion into the disc, and therefore,postoperative activity restrictions should be similar to those of an openmicroscopic lumbar discectomy. This activity modification will allow adequatetime for scar formation over the annulotomy defect and to prevent herniation/reherniation.

n COMPLICATIONS AND AVOIDANCE

Since the transforaminal endoscopic approach passes adjacent to the exiting spinalnerve root and Q11DRG, there is the potential for nerve irritation (dysesthesia) or overtnerve damage. Dysesthesia occurrence is 5% to 15% and is almost always transient.This rate of occurrence is similar to dysesthesia rates in posterior open discectomy,but in the latter situation, since the dysesthesia affects the retracted traversingnerve root that was already the source of radiculopathy, the transient persistent orincreased postoperative dysesthesia is generally not considered a complicationafter posterior discectomy. Both situations, however, are transient most of the time.Routine injection of steroid medication at the conclusion of the endoscopicdiscectomy has reduced the rates of dysesthesia significantly.

There is peer-reviewed literature on complication rates associated with spinalsurgery performed via an endoscopic transforaminal approach (14–17). Thepotential complications of the endoscopic transforaminal approach include nervedysesthesias (5–15% transient), persistent sensory deficit (1%), deep infection(0.65%), discitis (0.05%), dural tear (0.3%), thrombophlebitis (0.65%), bowel injury(0.004%), vascular injury (0%), and respiratory distress requiring intubation (0%) Q12.

Complications can be avoided by strictly adhering to the details in the KeyPoints section and principles of the YESS technique listed in Figures 4 and 6.Avoidance of complications is enhanced by the ability to clearly visualize normaland pathoanatomy, the use of local anesthesia and conscious sedation rather thangeneral or spinal anesthesia, and the use of a standardized needle placementprotocol (Fig. 7). The entire procedure is usually accomplished with the patientremaining comfortable during the entire procedure and should be done withoutthe patient feeling severe pain except when expected, such as during evocativediscography, annular fenestration, or when instruments are manipulated past theexiting nerve. Local anesthesia using 0.5% xylocaine allows generous use of thisdilute anesthetic for pain control and still allows the patient to feel pain when the

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60 n Yeung et al.

nerve root is manipulated. Thus, the awake and aware patient serves as the bestindicator to avoid any nerve irritation/damage. Dural tears can be treated with avisualized blood patch and observation because there is no “dead space” for CSFcollection/drainage.

n DISCUSSION/CONCLUSIONS

The endoscopic transforaminal approach (Fig. 8) is safe and efficacious as aminimally invasive alternative to posterior open discectomy, but does require aunique combination of skills not typically possessed by spine surgeons. Most spinesurgeons are unfamiliar and uncomfortable with the endoscopic transforaminal

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Technical “Pearls” and basic principles of the YESS technique:

1) Use the “Inside-out” technique: Start the endoscopy by first entering the disk and then address thepathology accordingly.

2) Sometimes (especially at L5/S1) partial lateral facetectomy may be required prior to entry into thedisk. Dock the long or short beveled cannula on the facet, resect the SAP undersurface from 3o’clock to 12 o’clock (right sided approach) or 12 o’clock to 9 o’clock (left sided approach) untilyou can gain safe entry into the disk space. Protect the existing nerve with the cannula, then use thestandard “Inside-out” technique.

3) The disk is the safest and best starting point. Both the disk and bone are safe harbors, you candock on these structures initially.

4) It is of extreme importance to use the specially designed cannulas with a penfield-like extension(Figure 7) to protect the exiting nerve when working in the foramen.

5) The patient is awake so use this to your advantage!! If significant leg pain is experienced, stopand re-evaluate the patient; ask them about the distribution of the pain and re-assess position usingfluoroscopy to prevent complications.

6) When bleeding is encountered advance the scope back into the disk and slowly pull back thescope cauterizing the bleeders from inside to out.

7) Use the “Inside-out” technique to your advantage: Once you are within the disk, the herniationis between you and the affected nerve, this is advantageous because it protects the nerve fromiatrogenic injury. When possible remove the herniation by pulling the herniation into the diskspace and then out the cannula.

Avoidance of potential complications.

FIGURE 6Technical “pearls” and basic principles of the YESS technique.

FIGURE 7Beveled cannulas allow a greater working area and enhance the ability to extract

extruded fragments and improve foraminal stenosis. The beveled Q13lip can also be rotatedand used to protect the exiting nerve root.


approach, and therefore the learning curve is a major obstacle to more widespreaduse of this technique. Prior experience with discography, transforaminal epiduralinjections, and arthroscopic experience is helpful in reducing the learning curve.Some surgeons feel that the potential for inferior outcomes that is associated withthe learning curve of this approach may not be justified when open posteriorapproaches dictate high success rates and outcomes. Perhaps this is why thistransforaminal approach is seldom utilized by the spinal surgeons despite the factthat the technique was first described by Kambin in 1991 (9,23). Advances inendoscopic instrumentation, optics, and working tools have made this approachsafer, easier to learn, and a versatile option not only for contained and foraminaldisc herniations, but for moderately extruded herniations, recurrent herniations,symptomatic annular tears, synovial cysts, foraminal stenosis, and infectiousdiscitis. The benefits of using muscle-spreading techniques under local anesthesia(avoiding general anesthesia) to access the foraminal anatomy and disc spacecannot be denied.

n FUTURE CONSIDERATIONS

Perhaps the best new indication for the use of this technique and approach is in therealm of motion preservation (nucleus replacement) or minimally invasive anteriorstabilization. One advantage of this approach stems from its ability to approach thedisc through the foramen, avoiding the morbidity associated with dural scarringencountered in revision lumbar surgery. The presence of scar tissue makestraditional posterior lumbar interbody fusion techniques difficult or impossible,

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Lumbar endoscopic posterolateral (Transforaminal) approach

Advantages Disadvantages

No general anesthesia Learning curve

No muscle stripping Size constraints of foraminal approach

No dural/root retraction (reducing epidural scarring) Expense of instruments/scope

No routine bony resection to access foraminal pathology Limited access to epidural space and

sequestered free fragments

Directly visualized nuclectomy or discectomy Limited endoscopic field of view

No anterior or posterior approach related morbidity Increased X-ray exposure (fluoro use)

Ease of exposure to lateral foraminal pathology Working in foramen near the DRG*

Reduced dead space for hematoma formation Initial unfamiliarity with endoscopic anatomy

*DRG= Dorsal Root Ganglia (of exiting nerve root)

FIGURE 8Lumbar endoscopic posterolateral (transforaminal) approach.

62 n Yeung et al.

but an interbody fusion via an endoscopic transforaminal approach would avoidthis issue. A biportal endoscopic fusion technique can be used to perform a radicaldiscectomy with burring of the endplates under direct visualization andsubsequent delivery of a cage and bone graft or a trans-sacral approach with theaxial-LIF technique. Transforaminal anatomy will limit the size of implant that canbe delivered; however, this problem can be overcome by using expandableinterbody or graft-containment devices.

This approach is also applicable as a vehicle for visualized total nuclectomywith endplate preservation and delivery of a nucleus replacement prosthesis.Endoscopic nuclectomy can be performed under direct visualization prior toimplanting an expandable nucleus replacement or possibly a disc replacement.Expandable nucleus replacement devices such as the Disc Dynamics DASCORnucleus replacement prosthesis and the Replication Medical Nudisc are well suitedfor this route of delivery.

n REFERENCES

1. Gogan WJ, Fraser RD. Chymopapain. A 10-year, double blind study. Spine 1992; 17:388–94.

2. Javid MJ, Norby E. Safety and efficacy of chymopapain (chymodiactin) in herniatednucleus pulposus with sciatica—results of a randomized, double blind study. JAMA1983; 249:2489–94.

3. Smith L. Chemonucleosis. Personal history, trials, and tribulations. Clin Orthop 1993;287:117–24.

4. Kambin P, Gellman H. Percutaneous lateral discectomy of the lumbar spine.A preliminary report. Clin Orthop 1983; 174:127–132.

5. Chaffin DP, Anderson GBJ. Occupational Biomechanics. New York: Wiley Interscience,1984, pp. 369–412.

6. Hermantin FU, Peters T, Quartararo L, Kambin P. A prospective, randomized studycomparing the results of open discectomy with those of video-assisted arthroscopicmicrodiscectomy. JBJS 1999; 81A:958–65.

7. Kambin P, Sampson S. Posterolateral percutaneous suction-excision of herniatedlumbar intervertebral discs. Report of interim results. Clin Orthop 1986; 207:37–43.

8. Kambin P, Brager MD. Percutaneous posterolateral discectomy. Anatomy andmechanism. Clin Orthop 1987; 223:145–54.

9. Kambin P, Schaffer JL. Percutaneous lumbar discectomy. Review of 100 patients andcurrent practice. Clin Orthop 1989; 238:24–34.

10. Kambin P. Arthroscopic microdiscectomy. Arthroscopy 1992; 8:287–95.11. Kambin P, O’brien E, Zhou L, Schaffer JL. Arthroscopic microdiscectomy and selective

fragmentectomy. Clin Orthop 1998; 347:150–67.12. Yeung AT. The evolution of percutaneous spinal endoscopy and discectomy: state of art.

Mt Sinai J Med 2000; 67:327–32.13. Yeung AT. Minimally invasive disc surgery with the Yeung endoscopic spine system

(YESS). Surgical Technology International VIII 1999; 1–11.14. Tsou PM, Yeung AT. Transforaminal endoscopic decompression for radiculopathy

secondary to non-contained intracanal lumbar disc herniation. Spine J 2002; 2:41–8.15. Yeung AT, Tsou PM. Posterolateral endoscopic excision for lumbar disc herniation. The

surgical technique, outcome and complications in 307 consecutive cases. Spine 2002; 27:722–31.

16. Jang JS, An SH, Lee SH. Transforaminal percutaneous endoscopic discectomy in thetreatment of foraminal and extraforaminal lumbar disc herniations. J Spinal DisordTech 2006; 19(5):338–43.

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17. Ahn Y, Lee SH, Park WM, Lee HY. Posterolateral percutaneous endoscopic lumbarforaminotomy for L5-S1 foraminal or lateral exit zone stenosis. Technical note. JNeurosurg 2003; 99 (Suppl. 3):320–23.

18. Mayer HM, Brock M. Percutaneous endoscopic discectomy: surgical technique andpreliminary results compared to microsurgical discectomy. J Neurosurg 1993; 78:216–25.

19. Lee SH, Uk Kang B. Operative failure of percutaneous endoscopic lumbar discectomy: aradiologic analysis of 55 cases. Spine 2006; 31(10):E285–E290.

20. Knight MTN, Goswami AKD. Endoscopic laser foraminoplasty. In: Savitz MH, Chiu JC,Yeung AT, eds. The Practice of Minimally Invasive Spinal Technique, 1st edn.Richmond, VA: AAMISMS Education, LLC, 2000, vol. 42, pp. 337–40.

21. Osman SG, Nibu K, Panjabi MM, Marsolais EB, Chaudhary R. Transforaminal andposterior decompressions of the lumbar spine. A comparative study of stability andintervertebral foramen area. Spine 1997; 22(15):1690–95.

22. Ito M et al. Transforaminal surgery for pyogenic thoracolumbar spondylodiscitis. Paperpresented at the American Academy of Minimally Invasive Spinal Medicine andSurgery 3rd World Congress, Dec 8–11, 2002, Phoenix, Arizona.

23. Schaffeer JL, Kambin P. Percutaneous posterolateral lumbar discectomy and decom-pression with a 6.9-millimeter cannula: analysis of operative failures and complications.JBJS (AM) 1991; 73:822–31.

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Percutaneous Transforaminal EndoscopicDiscectomy: The Thessys Method

5 Menno Iprenburg

n INTRODUCTION

Lately, both doctors and patients have shown a growing interest in minimallyinvasive spine surgery. This kind of procedure has proven to be a reliable treatmentfor several spinal disorders.

In the 1970s, Kambin (12), Kambin and Gellman (13), and Hijikata et al. (7)started to use specifically designed cannulas for performing a percutaneousdorsolateral nucleotomy and reported a satisfactory outcome of 75% with theirpatients. Later, Yeung and Tsou (19), Knight et al. (14), San Ho Lee Q1(1), andHoogland et al. (8–10), as well as others (2,5,6,21 Q2,15,16,18), used more laterallylocated entrance points with the help of smaller-caliber rod lens fiberoptics.

The procedure described below has been developed by Dr ThomasHoogland in cooperation with JoiMax in Germany. It has been practiced by mesince August 2004.

A special lateral transforaminal endoscopic entrance is used for the removalof herniated intervertebral disc material. This entrance has turned out to be lesstraumatic for the patient than the usual dorsal approach. Using the dorsalapproach, it is not always possible to avoid extensive sacrifice of vital stability. Themethod described here allows access to all herniated discs, except those that aredorsally dislocated.

After having gone through the learning curve, the documented recurrencerate with this method is low (3,4,6, 11,15,16,18). After gradual widening of theforamen in a step wise fashion with specially designed reamers, sequestrated discmaterial can be removed directly through the foramen. The patient, who can bepositioned in both the lateral and the prone position, can be addressed during thewhole procedure. Sedation is administered intravenously, individually adjusted,and also adjusted to the separate stages of the operation. I personally prefer thelateral position, although in the beginning, it might be rather difficult for surgeonswho are used to operating patients in the prone position.

The advantages of the lateral position are obvious. By placing a pillow underthe patient’s side, the foramen will slightly open up. Particularly with obesepatients, the pressure on the abdomen and the spine will be lower and the chancesof bleeding will be less. The lateral position allows both the anesthesist and thesurgeon a better view of the patient, thus enabling them to appreciate possible painreactions more effectively. The Laseque test can be carried out intraoperatively andthe patient can be asked to move the leg freely to see if the pain can still be evoked.

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65

The procedure can be performed in any outpatient surgical center, and thepatient usually leaves the clinic after two hours, walking! Q3Driving home as apassenger (with the back of the car seat at an angle of 45˚) is possible, if the journeyhome does not take longer than a few hours. The patient is then, however, advisedto walk a little every 30 minutes.

n INDICATION

Depending on the surgeon’s experience, this technique can be applied for anyinvasive surgical procedure for a herniated intervertebral disc. After some practice,even the L5-S1 level is possible. Sequestrated caudal disc material and usually alsothe cranial material can be carried out via this procedure under local anesthesiawith intravenous sedation. Dorsally sequestrated disc material is preferablyremoved through a dorsal entrance.

Recurring hernias in patients who have been dorsally operated before arerather operated via the lateral entrance through the foramen, so that existing scartissue does not hamper the surgeon. The treatment of foraminal stenosis, seen moreand more with older patients and with often considerable comorbidity, is very wellpossible with this technique.

n OPERATING TECHNIQUE

Positioning the patient well is essential. It must be possible, with the help of theimage intensifier, to view the spine closely in two directions (anteroposterior andlateral) at an angle of exactly 90˚. My personal preference, after approximately300 patients, would be the lateral position. Confirmation of the position of theannular tear, protrusion, and/or sequestrated disc material can be obtained byintraoperative discography.

The course of the operation is now explained using intraoperative images.The patient is lying on the left side (Fig. 1). The position of the iliac crest is marked

51525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100 FIGURE 1

66 n Iprenburg

and a line is drawn across the spinous processes. Depending on the patient’sposture, a line is drawn 14 to 15 cm from the center in case of a herniation at theL5-S1 level. The L4-L5 and L3-L4 levels each take 1 cm, respectively 2 cm less Q4.

Local anesthesia is administered at the place of entrance (Fig. 2). The needleis set and its position is checked by means of the image intensifier (Fig. 3). After the

101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150

FIGURE 2

FIGURE 3

Percutaneous Transforaminal Endoscopic Discectomy: The Thessys Method n 67

needle has reached the right position—the place with the largest prominence of thehernia—a guiding wire is introduced (Figs. 4 and 5).

Now, a first conical rod is introduced over the guiding wire and,consequently, the first, second, and third conical tube, in order to stretch the softparts. Afterwards, the second and third conical tubes are removed and the firstreamer is brought in, counter-clockwise (Fig. 6).

While conscientiously checking the image intensifier, a reaming is carried outup till 1 mm medially from the medial interpedicular line at the most Q5. Then, thefirst reamer, conical tube, and rod are removed. However, the guide wire remainsin place under all circumstances. For the patient, the first reaming is often the mostpainful. At the L5-S1 level, the procedure is usually carried out close to the iliaccrest. Passing the iliac crest might be painful, and it is recommended to extra-anesthetize the iliac crest locally as well.

Over the guide wire, a second conical rod is introduced up till the requiredlevel (check with the image intensifier), then the second conical tube, and thesecond reamer. The same applies for the third conical rod, tube, and reamer.

The patient is told to tell the surgeon if he or she experiences pain in the caseof L4-L5 and L5-S1 herniations under the knee. Sometimes, some pain is felt in thegreater trochanter region during reaming or even some radiating pain in theproximal lateral upper leg. Usually, however, the patient is comfortable and havinga conversation with the anesthesist (vocal anesthesia) (Fig. 7).

151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200

FIGURE 4 FIGURE 5

68 n Iprenburg

201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250

FIGURE 6

Q12

FIGURE 7


The working cannula can be introduced over the third conical rod. Its tipshould be located on the hernia (Figs. 8 and 9).

To achieve sufficient depth, it is often necessary to use the hammer for thelast stage after removing the guiding wire and the third conical rod (Figs. 10– 12).

251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300

FIGURE 8 FIGURE 9

FIGURE 10 FIGURE 11

70 n Iprenburg

The image intensifier is used continuously to check the position of theworking cannula.

Now the foraminoscope can be introduced and the hernia removed.Sometimes, a big sequester can be wholly removed immediately, but in mostcases, the “crabmeat” of the degenerated intervertebral disc has to be taken outwith a small pair of tongues, rongeurs, and a lot of patience (Fig. 13).

Intraoperatively, the patient can be asked to move the leg. After removing thehernia, the working cannula is also removed, and the skin is closed with an

301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350

FIGURE 12

FIGURE 13


intracutaneously dissolving stitch. Usually two hours after the operation, thepatient leaves the clinic (Figs. 14 and 15).

Our check-ups consists of a telephone call on the first postoperative day andafter two weeks. Then also physiotherapy is started Q6. A final consultation takesplace in the clinic after approximately six weeks. Further checks are carried outwith the help of the Swedish National Spine Register (20) preoperatively, after sixweeks, one year, and two years.

n Preoperative data: age, sex, smoking habits, working conditions, sick listing,consumption of analgesics and walking distance

n VAS Q7on back and leg painn Oswestryn SF 36n EuroQol questionnairesn Roland Q8

n OWN RESULTS

In the Wilhelmina Hospital in Assen and after 01.01.07 exclusively in RugkliniekIprenburg in Heerenveen, Netherlands, 300 patients were operated with thisprocedure between August 2004 and April 2007. Q9

Mostly they were patients with a herniation; some had foraminal stenosis,and some of the latter group also had a foraminal herniation. We retrospectivelyanalyzed the first 176 operated patients: 73 females and 103 males, average age45 ± 14 years (17 to 83 years).

LOCATION OF THE HERNIA

351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400

FIGURE 14 FIGURE 15

L3-L4 8L4-L5 63L5-S1 78Recurrent L4-L5 9Recurrent L5-S1 6HNP with foraminal stenosis 7Foraminal stenosis 5

72 n Iprenburg

De VAS scores for the back and the leg, the Roland and Oswestry scores were sentto all patients; 72% replied (127 patients). From these patients, the ones with firsthernias were picked (149 patients). They were 62 females and 87 males; age43 ± 12 years (17 to 82 years).

AGE DISTRIBUTION

05

101520253035404550

<20 20–30 30–40 40–50 50–60 60–70 >70

RADIAL COMPLAINTS

METHOD

RESPONDING VERSUS NONRESPONDING PATIENTS

n Responding patients are older (44 ± 12 years vs. 40 ± 13 years).n There were no other differences.

PROBLEMS AND COMPLICATIONSTotal group—176 patients:

n Eight recurrent complaintsn Ten reoperationsn Five microscopic discectomyn Four percutaneous transforaminal endoscopic discectomy (PTED)n One conversion in microscopic discectomyn All > 90% pain reductionn Two headaches (small dura leakage in medially located HNP)n One transient nerve palsy (resolved in 10 weeks)

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Right 65Left 80Medial 4

Status research 149 patientsResults questionnaires 106 patients (71%)


COMPLICATION VERSUS EXPERIENCE

In all cases, p¼0.103 In re-operations, p¼0.032.

QUESTIONNAIRES: WORK

0

5

10

15

20

25

30

35

40

Work

HeavyMediumLightUnemployedRetired

QUESTIONNAIRES: WALKING

01020

4030

5060708090

<100m100–500m500–1000m>1000m

QUESTIONNAIRES: PAIN

0

10

20

30

40

50

60

leg back

NoneStrong reductionSome reductionEqualWorse

451452453454455456457458459460461462463464465466467468469470471472473474475476477478479480481482483484485486487488489490491492493494495496497498499500

Q11

1–80 >101 Total

Headache 0 2 2Nerve palsy 0 1 1Reoperation 7 3 10

74 n Iprenburg

QUESTIONNAIRES: WORK POSTOPERATIVE

0

10

20

30

40

50

60

70

Work

Old job

Lighter

Sick leave

Unemployed

Retired

QUESTIONNAIRES: SATISFACTION

0

10

20

30

40

50

60

70

80

Much

Somewhat

Not

No opinion

OSWESTRY DISABILITY SCORE

0

10

20

30

40

50

60

70

80

Num

ber

Min Max

Minimal disability

Moderate disability

Severe disability

Bed bound

501502503504505506507508509510511512513514515516517518519520521522523524525526527528529530531532533534535536537538539540541542543544545546547548549550


ROLAND DISABILITY SCORE

0

5

10

15

20

25

30

Num

ber

3 5 8 11 13 15 17 19 21 23

Min Max

VAS BACK PAIN

0

10

20

30

40

50

60

70

80

Num

ber

0–20

20–40

40–60

60–80

80–100

Min Max

VAS LEG PAIN

0

10

20

30

40

50

60

70

80

Num

ber

0–20

20–40

40–60

60–80

80–100

Min Max

551552553554555556557558559560561562563564565566567568569570571572573574575576577578579580581582583584585586587588589590591592593594595596597598599600

76 n Iprenburg

EXPERIENCE VERSUS DURATION OF RADIATION EXPOSURE

P<0.00010

0,5

1

1,5

2

2,5

3

3,5D

urat

ion

(min

)

Experience

<80>80

p < 0.0001.In April 2007, after approximately 300 cases, the average time we use the

image intensifier in an L4-L5 case is 0.7 minutes, and in an L5/S1 case, 1.4 minutes.In October 2005 the Swedish National Spine Register published a report (20)

with the one-year follow-up results in microscopic disc herniation of 2796 patients.We compared the results of our endoscopically operated patients with the Swedishmicroscopically operated patients.

VAS: DUTCH ENDOSCOPIC SURGERY VERSUS SWEDISH MICROSCOPICSURGERY

0%10%20%30%40%50%60%70%80%90%

100%

PTED Sweden PTED Sweden

80–10060–8040–6020–400–20

Back: p ¼ 0.155; leg: p ¼ 0.018.

WALKING: DUTCH ENDOSCOPIC SURGERY VERSUS SWEDISHMICROSCOPIC SURGERY

P<0.001

0%10%20%30%40%50%60%70%80%90%

100%

PTED Sweden

>1000m500–1000m100–500m<100m

p < 0.001.

601602603604605606607608609610611612613614615616617618619620621622623624625626627628629630631632633634635636637638639640641642643644645646647648649650


SATISFACTION: DUTCH ENDOSCOPIC SURGERY VERSUS SWEDISHMICROSCOPIC SURGERY

0%10%20%30%40%50%60%70%80%90%

100%

PTED Sweden

No opinionNotSomewhatMuch

P=0.025

p < 0.025.

n FUTURE POSSIBILITIES

A B-Twin Cage placed as interbody spacer using the THESSYS system as accessand placement technology as well is shown in Figures Q1016 to 19*.

651652653654655656657658659660661662663664665666667668669670671672673674675676677678679680681682683684685686687688689690691692693694695696697698699700 FIGURE 16

78 n Iprenburg

701702703704705706707708709710711712713714715716717718719720721722723724725726727728729730731732733734735736737738739740741742743744745746747748749750

FIGURE 17

FIGURE 18


n CONCLUSIONS

We achieved good clinical results with our PTED under local anesthesia on anoutpatient basis; we got highly satisfied patients, and in most parameters, we hadbetter results than the Swedish register data.

As in every surgical intervention, the right diagnosis is essential for theresults. Patients with a hernia at the L4-L5 level are doing better than those withone at the L5-S1 level. Most likely, the results of L5-S1 will improve in time withincreased experience. At the L5-S1 level, we now have to ream twice or even threetimes to reach the medially located hernia.

The advantages are the following: only local anesthesia, reduced risk ofinfection, reduced risk of instability, less subsequent scars, open door surgery, andshort rehabilitation time. The disadvantages are the following: long learning curve,two-dimensional view, and initial expense.

The results with regard to patients with a foraminal stenosis are not asexcellent as those with regular disc herniations, but they are still rewarding.

The endoscopic method is not a simple one: it requires good three-dimensional imaginative powers; and for those who have no experience withendoscopic procedures, it will be harder to master.

It seems sensible to start performing the procedure under experiencedguidance after an adequate cadaver workshop, using slim patients with a discprolapse or herniation at the L4-L5 level.

The author holds the firm opinion that the PTED under local anesthesia on anoutpatient basis, as it has been developed by Dr Thomas Hoogland in Munich, willbe the golden standard in the future.

751752753754755756757758759760761762763764765766767768769770771772773774775776777778779780781782783784785786787788789790791792793794795796797798799800

FIGURE 19Source: Images courtesy of Dr Rudolf Morgenstern, Barcelona.

80 n Iprenburg

n REFERENCES

1. Ahn Y, Lee SH, Park WM, et al. Posterolateral percutaneous endoscopic lumbarforaminotomy for L5-S1 foraminal or lateral exit zone stenosis. Technical note.J Neurosurg 2003; 99(Suppl 3):320–3.

2. Alfen FM. Endoscopic transforaminal nocleotomy (ETN). Program Abstract at the 3rdDubai Spine Conference, Dubai, 2005.

3. Alfen FM, Lauerbach B. Technique and results of endoscopic transforaminalnucleotomy (ETN). Program Abstract at the 13th Congress of the InternationalMusculoskeletal Laser Society, Barcelona, 2006.

4. Gastambide D. Endoscopic posterolateral foraminotomy with instruments or laser forlateral lumbar stenosis. Program Abstract at the 17th Annual Meeting of theInternational Intradiscal Therapy Society, Munich, 2004.

5. Gibson A. Surgery for lumbar disc prolapse: evidence from the 2004 Cochrane review.Program Abstract at the 17th Annual Meeting of the International Intradiscal TherapySociety, Munich, 2004.

6. Hellinger J. Technical aspects of the percutaneous cervical and lumbar laser-disc-decompression and laser-nucleotomy. Neurol Res 1999; 21:99–102.

7. Hijikata S, Yamagishi M, Nakayama T, et al. Percutaneous nucleotomy. A new treatmentmethod for lumbar disc herniation. J Toden Hosp 1975; 5:5–13.

8. Hoogland T. Transforaminal endoscopic discectomy with foraminoplasty for lumbardisc herniation. Surg Techn Orthop Traumatol 2003; 55-120-C-40.

9. Hoogland T. Percutaneous nucleotomy of thoracic discs. Program Abstract at the 17thAnnual Meeting of the International Intradiscal Therapy Society, Munich, 2004.

10. Hoogland T, Godon T, Wagner C. Die endoskopische transforaminale Diskoplastik beiuberwiegend lumbalen Ruckenschmerzen. Program Abstract at the 52. Jahrestagungder Vereinigung Suddeutscher Orthopaden, Baden-Baden, 2004.

11. Iprenburg M. Percutaneous transforaminal endoscopic discectomy; the learning curveto achieve a more than 90% success rate. Program Abstract at the 19th Annual Meetingof the International Intradiscal Therapy Society, Phoenix, 2006.

12. Kambin P. Arthroscopic microdiscectomy: lumbar and thoracic. In: White AH,Schoffermann JA, eds. Spine Care, vol 2. St. Louis: Mosby, 1955, pp. 1002–16.

13. Kambin P, Gellman H. Percutaneous lateral discectomy of lumbar spine, a preliminaryreport. Clin Orthop 1983; 174:127–32.

14. Knight M, et al., eds. Endoscopic laser foramninoplasty. A two year follow-up of aprospective study on 200 consecutive patients. In: Gunzberg, Spalski, eds. LumbarSpinal Stenosis. Lippincott Williams and Wilkins, 1999, pp. 244–54.

15. Krzok G. Early results after posterolateral endoscopic discectomy with thermalannuloplasty. Program Abstract at the 17th Annual Meeting of the InternationalIntradiscal Therapy Society, Munich, 2004.

16. Levinkopf M, Caspi I, et al. Posterolateral endoscopic discectomy. Program Abstract atthe 18th Annual Meeting of the International Intradiscal Therapy Society, San Diego,2005.

17. Parke WW. Clinical anatomy of the lower lumbar spine. In: Kambin P, ed. ArthroscopicMicrodiscectomy, Minimal Intervention in Spinal Surgery. Baltimore: Urban andSchwarzenberg, 1991, pp. 11–29.

18. Schubert M, Hoogland T. Endoscopic transforaminal nucleotomy with foraminoplastyfor lumbar disc herniation. Oper Orthop Traumatol 2005; 17:641–61.

19. Yeung A, Tsou P. Posterolateral endoscopic excision for lumbar disc herniation. Spine2001; 27(7):722–31.

20. Stromqvist B, Jonsson B, Fritzell P, Hagg O, Larsson BE, Lind B. Results One-yearReport of the Swedish National Spine Register. Acta Orthop 2005; 76(Suppl 319).

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Use of Navigation-Assisted Fluoroscopyto Decrease Radiation Exposure DuringMinimally Invasive Spine Surgery

6 Choll W. Kim

n INTRODUCTION

Lumbar spinal fusion is a procedure performed for spinal instability, spondylo-listhesis, trauma, and symptomatic degenerative disc disease. The purpose ofspinal fusion is to eliminate motion at a painful and/or unstable motion segment.It is now possible to achieve greater than 90% successful fusion withcircumferential fusion techniques such as transforaminal lumbar interbody fusion(TLIF) (1–3). However, this technique most commonly employs open exposures,which may involve extensive muscle stripping and aggressive, prolongedretraction. It is known that these events damage muscle tissue and inhibit musclefunction (4–7). This may lead to extended hospital stay, prolonged disability, andsuboptimal long-term clinical outcomes (8). The use of minimally invasive spine(MIS) surgical techniques strives to avoid the collateral damage associated withopen surgery. The concept of MIS surgery rests on the tenet of minimizing softtissue disruption. Although the incision size of MIS procedures tends to be lessthan that of open procedures, it is the decreased muscle stripping and retractionpressure that constitutes less invasive surgery. This is best accomplished bylimiting the exposure to the necessary surgical corridor and employing specializedretractors that distribute pressures evenly.

n RADIATION EXPOSURE DURING MIS SURGERY

Although numerous MIS systems have been developed, MIS surgery remainstechnically challenging. The learning curve is difficult and most surgeons incurrent practice have no formal training in MIS surgery (9). As a consequence,most spine surgeons have been reticent to adopt these techniques into standardpractice. An equally important drawback of MIS surgery is the need for real-timeintraoperative fluoroscopy. Intraoperative fluoroscopy is required to localize thecorrect level, expose the surgical corridor, and guide insertion of implants.Intraoperative fluoroscopy may also be used to assess the extent of decompression,discectomy, and placement of interbody implants. During this portion of theprocedure, the entire surgical team (surgeon, assistant surgeon, and scrub nurse)must remain at the surgical field, directly adjacent to the image intensifier. While it

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Choll W. Kim Department of Orthopaedic Surgery, University of California San Diego and theSan Diego VA Medical Center, San Diego, California, U.S.A.

83

is routine to wear lead gowns, the use of thyroid shields, protective eyewear, andprotective gloves is uncommon.

The National Council on Radiation Protection and Measurements (NCRP)has established annual limits of exposure to areas of the body (10). The limit for theskin, extremities (hand), and body organs is 50 rem per year. For the eye, it is 15rems per year. A spine surgeon using three minutes of fluoroscopy will reach thelimit of 50 rems per year with slightly over 200 cases. This is well within theparameters of current practice for most active spine surgeons engaged in MISsurgery (11). For the eye, this will be less. Unless surgeons begin using thyroidshields, protective glasses, and gloves, many will exceed the recommended limitson a regular basis. Furthermore, newer minimally invasive procedures such askyphoplasty and vertebroplasty use significantly more radiation (12). In terms ofrelative risk, a spine surgeon performing MIS procedures such as kyphoplastyusing a lead gown will be at 50 times greater risk of fatal cancer compared to a hipsurgeon (12). Furthermore, it is important to emphasize that tolerance limits arederived from laboratory experiments in animals such as Drosophila (fruit flies) andmice. For humans, most data are extrapolated from high-dose exposures over shortperiods of time. There are no good data on the risk of long-term, repetitive, low-dose radiation exposure. The handbook from the NCRP states that “extrapolationof risks from exposures at high doses, in addition to the inherent experimentalerrors in the data, is most likely the predominant uncertainty in the estimate of riskat low doses” (10). This uncertainty can lead to anxiety and stress, which bythemselves itself can be considered health hazards. The use of intraoperativefluoroscopy is also cumbersome and inconvenient. The surgical team must donprotective equipment such as lead aprons and thyroid shields. Protective eyewearand gloves are also recommended but are rarely used by spine surgeons (10). Thisgear can be extremely uncomfortable. Furthermore, the c-arm encroaches upon thesurgical field and often forces the surgical team to work in awkward positions.

n USE OF IMAGE GUIDANCE FOR MIS SURGERY

Image-guided spine surgery using computer-assisted navigation is a promisingtechnique that addresses many of these concerns. Image-guided surgery relies onglobal positioning technology to orient the spine in three-dimensional space(13–17). Using tools that are in turn registered to the image-guidance system,instruments can be navigated to the proper location and trajectory on the spine.Thus, the need for intraoperative fluoroscopy can be greatly reduced.

Despite the fact that navigation has been available for clinical use since theearly 1990s, it has not yet gained wide acceptance by spine surgeons. The reasonsfor this lack of interest are several. First, a high-resolution CT scan reconstruction isneeded for image registration. As most spine surgeries are performed withoutpreoperative CT imaging, this requires the spine surgeon to obtain a separate,previously unnecessary test. This new burden also exposes the patient toadditional ionizing radiation. Second, the step of pinpointing fudicials is timeconsuming and adds an element of subjectivity. Relying on intraoperativeidentification of fudicial points seems dichotomous to the highly objective tasksperformed by the navigation computer. Finally, most spine surgeons did not relyon intraoperative fluoroscopy at the time navigation was introduced. In the early1990s, most spine surgeries were performed open with clear anatomic landmarks.

51525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100

84 n Kim

Radiography was mainly used at the beginning of the case to localize the levels andat the end to confirm satisfactory implant position. Thus, even with the advent ofmore simplified forms of navigation, such as virtual fluoroscopy or three-dimensional fluoroscopy using the Iso-C device, there was simply no clinicalneed. With the emergence of MIS surgery, the need for intraoperative fluoroscopyhas increased considerably. With MIS surgery, fluoroscopy is required to guidesurgical dissection and insertion of spinal implants within a limited field of view.This makes MIS surgery without fluoroscopy extremely challenging andpotentially dangerous. This increased reliance on intraoperative fluoroscopy, alongwith its associated exposure to ionizing radiation, now makes the use of navigationtechnology attractive and worthwhile.

n NAV-MIS TLIF TECHNIQUE

Navigation-assisted fluoroscopy can be used for any MIS surgery. The mostpopular MIS technique is TLIF. A convenient application of navigation-assistedfluoroscopy is described for this procedure, termed “NAV-MIS TLIF.” With thepatient prone on a radiolucent table, the patient reference tracker is inserted intothe posterior superior iliac spine (PSIS). The PSIS is manually palpated and a 5mmfluted pin is tamped into place using a sleeve guide (Fig. 1A). A standard 9-inchc-arm (OEC 9800, GE Medical Systems) is fitted with the navigation tracker toallow image capture by the navigation computer. Multiple images of the lumbarspine are obtained and stored in the navigation system. At least one trueanteroposterior (AP) and lateral image as well as oblique images in line with thepedicle are obtained. During image acquisition, the surgical team can step awayfrom the surgical field and behind lead shielding. No lead aprons are worn by thesurgical team.

Once the desired images are obtained, the c-arm is taken out of the surgicalfield. Surgery is now performed using the stored images from the navigationsystem. The navigation pointer is used to plan the incision. The entry point to apath directly in line with the disc space on the lateral image and down the lateralaspect of the facet joint on the AP and oblique images is marked (Fig. 1). A 3.5 cmincision is made. This localization is performed solely with the images stored in thenavigation terminal. No fudicial points or other registration methods are used. Thepatient tracker placed previously on the iliac crest serves as the reference point tosynchronize the virtual image with the anatomic spine.

The incision site is infiltrated with 0.25% marcaine and epinephrine(1:100,000 dilution). The skin and dorsal fascia are incised and blunt fingerdissection is performed between the multifidus and longissimus muscles. Thelateral border of the superior articular process is palpated and the navigationpointer is used to confirm the correct level. Q1An expandable retractor (QuadrantSystem, Medtronic Sofamor Danek, Memphis, TN) is deployed, using thenavigator pointer to position the retractor directly over the facet joint and in linewith the disc space. Gentle electrocautery is used to expose the pedicle entrypoints. The pedicle is entered using the navigation awl (or drill with a universalnavigation attachment), blunt pedicle probe, and tap (Fig. 1). Using a split-screenmonitor, four separate images can be viewed simultaneously (Fig. 2). The trajectoryin both AP and lateral planes, along with the desired screw diameter and length, isdetermined. The pedicle screw of the appropriate size is inserted using the

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Use of Navigation-Assisted Fluoroscopy n 85

navigation screw driver (Fig. 3). All screws are placed prior to the discectomy. It isimportant to perform all critical navigation steps prior to the discectomy. Afterdiscectomy, the motion segment becomes hypermobile and thus changes itsposition relative to the original images.

The navigation pointer is used to locate and guide the exposure of theinferior articular process, lamina, and pars intereticularis of the cephalad level.A complete facetectomy is performed using a high-speed burr and Kerrisonrongeurs. The exiting and traversing nerve roots are identified and carefullydecompressed back to the base of the cephalad and caudad pedicles, therebyobtaining a “pedicle-to-pedicle” exposure. Blood vessels within Kambin’s triangleare gently coagulated with bipolar electrocautery. Care is taken to avoid unduemanipulation of the dorsal root ganglion of the exiting nerve root. A complete

151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200

FIGURE 1Use of a navigation probe to plan incision and exposure. All images are captured in

the navigation system at the beginning of the procedure and the c-arm is taken out of thesurgical field during surgery. The navigation computer stores all images as virtual images.Various navigation instruments can now be used with the virtual images, which are overlaidonto the image of the navigation tracking device. The navigation probe (white arrow) isplacedon theskin toplan thecenter of the incisionand the trajectoryof theapproach (A,C,D).A universal tracking handle can accommodate various additional tools needed for pediclescrew insertion, including awls, pedicle probes, and taps (B). In the anteroposterior plane,the tip of the probe is docked lateral to the pedicles (C). In the lateral image, the probe isdirectly in linewith thedisc space (D). The tip canbeextendedby thenavigation system toaidin alignment. The probe is pictured in purple and the extension in red (C,D).

86 n Kim

decompression of the central canal and contralateral nerve roots is obtained byundercutting the spinous process and contralateral lamina using the MISlaminoplasty technique as described by Weiner et al. and McCulloch et al. (18–21).

A subtotal discectomy is performed using a combination of periostealelevators, curettes, and pituitary rongeurs. If necessary, a navigation osteotome isused to remove the overhanging rim of the posterior vertebral endplate (Fig. 3C).Navigated, angled curettes are used to remove disc from the contralateral side(Fig. 3D). The navigation pointer can be used to determine the extent of thediscectomy anteriorly (Fig. 3E). A bulleted interbody spacer is inserted and tampedto the anterior aspect of the disc space. The general position of the spacer can bedetermined using the navigation pointer. Bone graft is placed within the cage andpacked behind the cage. Final c-arm images are obtained to confirm satisfactoryimplant position and spinal alignment. Again, the surgical team steps away fromthe operative field during image acquisition.

TIPS AND PEARLS OF THE NAV-MIS TLIF PROCEDUREThe placement of the patient tracker plays a key role in the accuracy of thenavigation system. The PSIS is used since its location can be easily palpated

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FIGURE 2Use of simultaneous, multiplanar views during surgery. Using a four-panel split-

screen format, anteroposterior, lateral, and oblique views of the spine can be visualizedsimultaneously. Trajectories in the anteroposterior (A) and lateral (B) plane can ensureoptimum screw position. Oblique views provide additional information to help preventpedicle breaches (C). The contralateral oblique (D) is not necessary for screw insertion,and thus alternate images can be used, such as another lateral image at a distantsurgical level.


without the need for fluoroscopy (Fig. 1A). The patient tracker must be placedstrategically to avoid obscuring the surgical field. If placed too close to the incisionsite, one may encounter difficulty with instruments such as curettes, which arelong and often need to be angled in various directions. Similarly, the tracker should

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FIGURE 3Use of navigation for pedicle screw insertion and discectomy. Once all pedicle

screws are inserted (A,B), subtotal discectomy is performed using various navigationinstruments such as osteotomes (C) and angled curettes (D). The navigation pointer isused to determine the extent of discectomy anteriorly (E) and location of the interbodyspacer relative to the midline (F).

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not obscure the field during c-arm imaging. Placement of the tracker at the PSISangled slightly cephalad makes it caudal to the incision site and thus avoids bothof these potential difficulties.

It is important to consider that the pelvis and the lumbar spine have thepotential of moving relative to each other during surgery. Therefore, it isimperative that patient position not be perturbed once the images are downloadedinto the navigation system. Since the image on the navigation computer is a virtualimage, care must be taken to avoid manipulating the spine or moving its positionwhen applying pressure on instruments such as the awl or tap. The position on thenavigation screen is best obtained with no stress or moments on the instrumentwhen it is engaged in the spine. The navigation image should be examined withthe instrument “where it lies.” Intermittent verification of navigation instrumentsby checking known anatomic landmarks during surgery provides confirmatoryinformation. For example, the edges of the transverse processes, the lateral borderof the pars intereticularis, the inferior border of the cephalad pedicle, and thesuperior border of the caudad pedicle can be readily visualized both anatomicallyand fluoroscopically. If at any time during the procedure, the navigation imagedoes not coincide with the expected anatomic landmarks, the c-arm should bebrought back into the field and a fresh set of navigation images obtained.

Studies show that the accuracy of screw placement using navigation-assistedfluoroscopy is approximately 1 to 2mm up to the level of L2 (17,22,23). This degreeof variability is not well suited for procedures that require exquisite precisionsuch as odontoid screws. However, employing other surgical cues, such as tactilefeedback and visualized anatomic landmarks, can aid in the safe placement of

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FIGURE 4 Q1Cadaveric study comparing MIS TLIF using navigation-assisted fluoroscopy(NAV, black bars) versus standard fluoroscopy (FLUORO, white bars). A statistical analysiswas performed using one-way ANOVA with p <0.05. Standard deviations are shown withvertical lines. Statistically significant differences were found for the SET-UP time (minutes)and C-ARM time (seconds). The remaining parameters showed no statistically significantdifferences. Abbreviations: MIS, minimally invasive spine; TLIF, transforaminal lumbarinterbody fusion.


pedicle screws. For example, the pedicle entry point can be directly visualized,the cephalad and caudal borders of the transverse process palpated, thepars intereticularis visualized, and the inner walls of the pedicle palpated with aball-tip feeler.

CADAVERIC STUDY OF NAV-MIS TLIFEighteen unilateral TLIFs were performed on four cadaveric specimens from L1-L2through L5-S1 as described previously ( Q2Schwender et al. and Ozgur et al.). Eachlevel and side was randomized using a latin-square design prior to examination ofthe cadavers. Two disc space levels were omitted due to severe disc space collapse.A navigation-assisted fluoroscopy system (FluoroNav, Medtronic Navigation,Louisville, CO) was used to perform nine separate TLIF procedures as describedbelow (NAV group). Q3The comparison group underwent MIS TLIF using standardfluoroscopic techniques (FLUORO group). In the FLUORO group, the c-arm (OEC9800) was used in the AP position to guide a parasagittal incision analogous to theNAV group. Once the retractors were deployed over the surgical target, the c-armwas arced under the surgical table to obtain lateral images. Using an anatomictechnique, the entry point of the pedicle was created with a small burr. The pediclewas entered with a gear-shift probe, tapped, and the screw inserted usingintermittent, lateral fluoroscopic imaging.

Specified steps in the procedure were timed by a separate observer. Set-uptime begins at the completion of draping and lasts until the skin incision is made.For the NAV group, this includes insertion of the patient reference device (tracker)and acquisition of all the images necessary for the remainder of the surgery.Approach time is from skin incision until the retractor is fully deployed. Exposuretime begins once the retractor is deployed and ends when the facet, hemilamina,and pedicle entry points are exposed. Screw insertion time is averaged for twoscrews. Facetectomy time begins immediately after the last screw is inserted andlasts until the entire facet joint is removed and the nerve roots are fullydecompressed. The spinous process and contralateral lamina are undercut vialumbar laminoplasty technique until the contralateral dural edge can be visualizedas described by McCullough et al. (20,21). Discectomy time is from annulotomy toinsertion of the interbody cage. Surgery time is the total time for the procedure andbegins when draping is complete and lasts until the locking nuts are tightened withthe torque wrench. Radiation detection badges were worn by the surgeon on theoutside of the lead protective gear, directly anterior to the thyroid. A separatebadge was worn for each procedure and analyzed by an independent lab(Landauer, Glenwood, IL). All procedures were performed by a single surgeon(the author).

For most key steps, the times were similar between the NAV group and theFLUORO group. No statistically significant differences were obtained forapproach, exposure, screw insertion, facetectomy/decompression, and totalsurgical times. Statistically significant differences were obtained for the set-uptime and total fluoro time. The set-up time for the NAV group averaged9.67 minutes [standard deviation (SD)¼ 3.74] compared to 4.78 minutes(SD¼ 2.11) for the FLUORO group (p¼ 0.034). However, the total fluoro timewas higher for the FLUORO group compared to the NAV group (41.9 seconds vs.28.7 seconds, p ¼ 0.042). Total surgery time for the NAVand FLUORO groups were50.2 minutes (SD¼ 10.2) and 46.8 minutes (SD¼ 4.8), respectively (p¼ 0.39).

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Radiation exposure is undetectable when navigation-assisted fluoroscopy is used(NAV group). In contrast, an average 12.4 mREM of radiation exposure is deli-vered to the surgeon during unilateral MIS TLIF procedure without navigation(FLUORO group).

CLINICAL STUDIES OF NAV-MIS TLIFTen patients underwent treatment of grade 1 spondylolisthesis via NAV-MIS TLIF.Intraoperative and perioperative parameters were obtained prospectively. Timesfor specific steps of the procedure, including time for each screw insertion, weremeasured by an independent observer (Table 1). Surgery time, estimated blood loss(EBL), intraoperative and perioperative complications, and hospital stay wereassessed. The total fluoroscopy time was determined from the internal timer of thec-arm. In addition, eight patients undergoing MIS TLIF using standard fluoro-scopic technique without navigation were retrospectively studied. Information ontotal operation room (OR) time, EBL, hospital stay, and complications wereobtained from chart review. Total fluoro time was obtained from a radiation logsheet used to monitor c-arm use. These values are also obtained from the internaltimer of the c-arm.

The clinical results of the 10 patients undergoing the NAV-MIS TLIFprocedure were assessed prospectively. Table 1 shows specific times for set-up,exposure, screw insertion time, facetectomy/decompression, discectomy/cageinsertion, and total surgery time. All procedures were performed by a singlesurgeon (the author) using the same c-arm. The set-up time was 18.0 minutes(SD¼ 6.8, range 5–26). This time began when the patient was fully draped andincluded the time for the patient tracker to be inserted into the PSIS, acquisition ofall the c-arm images into the navigation system, and the start of the incision.The approach time was 22 minutes (SD¼ 11.9, range 6–45). The average time forscrew insertion was 10.3 minutes per screw (SD¼ 5.7, range 2–24). All screws werein satisfactory position as determined from postoperative radiographs indepen-dently evaluated by a musculoskeletal radiologist. The time for facetectomy and

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TABLE 1 Summary of Intraoperative and Perioperative Clinical Results

Navigation assisted Fluoro

Set-up time 18 (±6.8 SD)

Approach 24.3 (±10.8 SD)

Facetectomy 55.0 (±24.5 SD)

Discectomy 27.6 (±8.1 SD)

Cage insertion 14.0 (±8.2 SD)

Screw insertion 10.3 (±5.7 SD)

Total OR time 67.9 (±37.4 SD) 293.4 (±62.9 SD)Fluoro time (sec) 57.1 (±34.5 SD) 147.0 (±73.3 SD)EBL (mL) 200 (±77.7 SD) 206.2 (±78.8 SD)Hospital stay (days) 3.6 (±0.7 SD) 3.4 (±0.5 SD)Complications None CSF leak (n ¼1)

Abbreviations: CSF, cerebrospinal fluid; EBL, estimated blood loss; OR, operation room; SD, standard

deviation.


contralateral decompression using the MIS laminoplasty technique was 54.9 min-utes (SD¼ 22.7, range 27–94). The time for discectomy was 28.5 minutes (SD¼ 7.9,range 17–39).

Table 1 compares NAV-MIS TLIF with MIS TLIF without navigation for totalfluoroscopy time, total OR time, and hospital stay. No statistically significantdifferences are noted for OR time, EBL, and hospital stay. There is a statisticallysignificant decrease in total fluoro time with navigation. The total fluoro time forthe NAV group was 57.1 seconds (SD¼ 37.3, range 18–120) compared to147.2 seconds (SD¼ 73.3, range 73–295) for the FLUORO group (p¼ 0.02). Noinadvertent durotomies, postoperative weakness, or new radiculopathy werenoted in the NAV group. One inadvertent durotomy was encountered in theFLUORO group, which was repaired intraoperatively without clinical sequelae.

n CONCLUSIONS

Navigation-assisted fluoroscopy is a promising method for decreasing radiationexposure during MIS surgery. The NAV-MIS TLIF method is simple andstraightforward, with an acceptable clinical safety profile. This techniquespecifically addresses the original drawbacks of navigation as they pertain tospine surgery. First, no significant deviation from standard techniques is required.Many of the concepts of MIS surgery remain unchanged. Second, no additionalpreoperative images are necessary. There is no need for fudicial readings to “matchup” the navigation image with a CT scan. In fact, fudicial readings are unavailablein MIS surgeries where the spine is not fully exposed. Third, the navigation imagesare similar to the fluoroscopic images obtained during standard MIS surgery. AP,lateral, and oblique images are used to guide instruments into the pedicle. A majoradvantage of navigation-assisted fluoroscopy is that four images can be viewedsimultaneously. Furthermore, since all navigation images are obtained at thebeginning of surgery, there is less repositioning of the c-arm. This can beadvantageous when the fluoroscope technician is inexperienced and/or uninter-ested. The computer’s versatile programming function offers numerous otheradvantages. Desired screw sizes and rod lengths can be readily determined. Theextent of the discectomy and the position of the interbody graft can be assessed.Operating room ergonomics is also improved. With a clear surgical field, surgeonscan assume a comfortable position during surgery. The operating microscope canbe brought in without interference from the c-arm. The need for heavy, restrictiveprotective gear is eliminated since all navigation images are obtained while thesurgical team steps away from the path of radiation scatter.

Although there is a preconception that use of navigation-assisted fluoroscopyadds time-consuming tasks to the procedure, our cadaveric studies show thatoverall surgical times are not affected. There is additional time needed at thebeginning of the procedure to acquire and download all the images into thenavigation computer. This step can be perceived as excessively long, particularly tothe expeditious spine surgeon. However, overall fluoroscopy time is decreasedwith navigation. During standard fluoroscopic MIS surgery, the c-arm must bebrought in and out of the surgical field during surgery. With each repositioning,several images must be taken to reestablish the original views. By avoiding thesesteps, the additional time spent for navigation set-up is offset by the time needed totake additional images and for the fluoroscope technician to reposition the c-arm.

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Further decreases in surgical time are anticipated as surgeon experience increasesand improved navigation instruments designed for MIS surgery are developed.The use of navigation is the first part of a stepwise progression of appliedadvanced technology for MIS surgery. Further advancements will include thecoordinated use of neurophysiologic monitoring, real-time three-dimensionalimaging, and robotics.

n REFERENCES

1. Salehi SA, Tawk R, Ganju A, LaMarca F, Liu JC, Ondra SL. Transforaminal lumbarinterbody fusion: surgical technique and results in 24 patients. Neurosurgery 2004;54(2):368–374; discussion 74.

2. Lauber S, Schulte TL, Liljenqvist U, Halm H, Hackenberg L. Clinical and radiologic2–4-year results of transforaminal lumbar interbody fusion in degenerative and isthmicspondylolisthesis grades 1 and 2. Spine 2006; 31(15):1693–8.

3. Hackenberg L, Halm H, Bullmann V, Vieth V, Schneider M, Liljenqvist U.Transforaminal lumbar interbody fusion: a safe technique with satisfactory three tofive year results. Eur Spine J 2005; 14(6):551–58.

4. Gejo R, Matsui H, Kawaguchi Y, Ishihara H, Tsuji H. Serial changes in trunk muscleperformance after posterior lumbar surgery. Spine 1999; 24(10):1023–28.

5. Kawaguchi Y, Matsui H, Tsuji H. Back muscle injury after posterior lumbar spinesurgery. Part 1: histologic and histochemical analyses in rats. Spine 1994; 19(22):2590–97.

6. Kawaguchi Y, Matsui H, Tsuji H. Back muscle injury after posterior lumbar spinesurgery. Part 2: histologic and histochemical analyses in humans. Spine 1994; 19(22):2598–602.

7. Zhao WP, Kawaguchi Y, Matsui H, Kanamori M, Kimura T. Histochemistry andmorphology of the multifidus muscle in lumbar disc herniation: comparative studybetween diseased and normal sides. Spine 2000; 25(17):2191–99.

8. Datta G, Gnanalingham KK, Peterson D, et al. Back pain and disability after lumbarlaminectomy: is there a relationship to muscle retraction? Neurosurgery 2004; 54(6):1413–1420. discussion 20.

9. Newton PO, Shea KG, Granlund KF. Defining the pediatric spinal thoracoscopylearning curve: sixty-five consecutive cases. Spine 2000; 25(8):1028–35.

10. NCRP R. Limitation of Exposure to Ionizing Radiation. Bethesda: National Council onRadiation Protection and Measurements, 1993.

11. Rampersaud YR, Foley KT, Shen AC, Williams S, Solomito M. Radiation exposure to thespine surgeon during fluoroscopically assisted pedicle screw insertion. Spine 2000;25(20):2637–45.

12. Theocharopoulos N, Perisinakis K, Damilakis J, Papadokostakis G, Hadjipavlou A,Gourtsoyiannis N. Occupational exposure from common fluoroscopic projections usedin orthopaedic surgery. J Bone Joint Surg Am 2003; 85A(9):1698–703.

13. Schlenzka D, Laine T, Lund T. Computer-assisted spine surgery. Eur Spine J 2000;9(Suppl. 1):S57–S64.

14. Kalfas IH. Image-guided spinal navigation. Clin Neurosurg 2000; 46:70–88.15. Glossop ND, Hu RW, Randle JA. Computer-aided pedicle screw placement using

frameless stereotaxis. Spine 1996; 21(17):2026–34.16. Merloz P, Tonetti J, Pittet L, et al. Computer-assisted spine surgery. Comput Aid Surg

1998; 3(6):297–305.17. Foley KT, Simon DA, Rampersaud YR. Virtual fluoroscopy: computer-assisted

fluoroscopic navigation. Spine 2001; 26(4):347–51.18. Weiner BK, Walker M, Brower RS, McCulloch JA. Microdecompression for lumbar

spinal canal stenosis. Spine 1999; 24(21):2268–72.19. Weiner BK, Fraser RD, Peterson M. Spinous process osteotomies to facilitate lumbar

decompressive surgery. Spine 1999; 24(1):62–6.

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20. McCulloch JA, Weiner BK. Microsurgery in the lumbar intertransverse interval. InstrCourse Lect 2002; 51:233–41.

21. McCulloch JA, Snook D, Kruse CF. Advantages of the operating microscope in lumbarspine surgery. Instr Course Lect 2002; 51:243–45.

22. Rampersaud YR, Pik JH, Salonen D, Farooq S. Clinical accuracy of fluoroscopiccomputer-assisted pedicle screw fixation: a CT analysis. Spine 2005; 30(7):E183–E190.

23. Holly LT, Bloch O, Johnson JP. Evaluation of registration techniques for spinal imageguidance. J Neurosurg Spine 2006; 4(4):323–28.

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Pedicle-Targeting Techniques for MinimallyInvasive Lumbar Fusions

7 Mark J. Spoonamore

n INTRODUCTION

Although many areas of surgery have seen revolutionary advances over the last 20to 60 years, spinal surgery has seen the majority of changes since the millennium,particularly in the realm of minimally invasive spinal surgery. Refined techniquesfor percutaneous placement of pedicle screws became available in 2000 (1–3), andcontinue to make strides of improvement as each year goes by. Initially, thetechniques involved placement of screws through an open, Wiltse approach (Fig. 1)or a less-invasive modified Wiltse approach, but the surgery was not trulypercutaneous or minimally invasive.

Now, many instrumentation systems exist that allow for screws to bepercutaneously placed by using fluoroscopic guidance. However, as techniquesbecome refined, new skills and competencies must be learned and mastered by thesurgeons who perform them. Nearly all spinal surgeons practicing today are welltrained and well versed in the placement of pedicle screws using an opentechnique, yet the majority of surgeons have minimal or no experience in thepercutaneous placement of pedicle screws. This chapter explains in detail specificsurgical techniques for fluoroscopic pedicle targeting and accurate percutaneousplacement of pedicle screws.

n INDICATIONS

Percutaneous pedicle screw systems are indicated for patients requiring single- ormultiple-level instrumentation for stabilization of posterior fusion (4–6).Indications also include patients requiring posterior instrumentation with fusionas an adjunct for anterior interbody fusion. Simultaneous multilevel laminectomyand percutaneous pedicle screw instrumentation and fusion may be relativelycontraindicated since this is technically demanding, and multiple large incisionsmay lead to skin/tissue bridging necrosis.

n OVERVIEW

There are two commonly utilized techniques to insert pedicle screws via aminimally invasive, percutaneous approach. The most common method is the

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Mark J. Spoonamore, Department of Orthopaedic Surgery, Keck School of Medicine, University ofSouthern California, Los Angeles, California, U.S.A.

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anterior–posterior (AP) technique, wherein the guidance pins, wires, and screwsare placed primarily with the c-arm in the AP position. The second technique, andthe author’s preferred technique, is called the bull’s-eye technique, in which theguidance pins, wires, and screws are placed with the c-arm in the oblique position,so as to have a fluoroscopic view directly down the pedicle being targeted. Whenthe pin is perfectly in the middle, it resembles a bull’s-eye, hence the name “bull’s-eye technique.”

There may be other techniques to place pedicle screws under fluoroscopicguidance; however, there are none described in the medical literature to date. Mostsurgeons performing percutaneous pedicle screw fixation utilize one of the twoabove described techniques, or a combination of the two. The importance ofchecking the oblique (bull’s-eye) view, however, cannot be overemphasized. It isthe most reliable image to verify that a pedicle has been accurately penetrated andthat a breach, particularly a medial wall breach, has not occurred.

n POSITIONING AND SET-UP

Both methods involve identical patient positioning and preparation (Fig. 2).A general anesthetic is required, and many surgeons prefer to have a patientadequately paralyzed so as to ensure a patient will not move at all during thesurgery. If continuous Q1EMG and/or pedicle screw stimulation is to be utilized

FIGURE 1Wiltse paraspinal muscle-splitting approach between multifidus, longissimus,

and iliocostalis.

96 n Spoonamore

(Fig. 3), a patient must not be paralyzed but yet the patient must be very deeplyanesthetized so that there is no movement during the surgery.

The patient must be placed in the prone position on a radiolucent operatingtable, such as a Jackson table (Fig. 2). Great care must be taken to be sure the patient

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FIGURE 2The two most common methods of targeting pedicles are best done on a

radiolucent operating-room table with the patient in a prone position. In the AP technique,the guidance pins, wires, and screws are placed primarily with the c-arm in the APposition. The second technique, and the author’s preferred technique, is called the bull’s-eye technique, and is used to describe the method of placing the guidance pins, wires, andscrews with the c-arm in the oblique position, so as to have a fluoroscopic view directlydown the pedicle being targeted. Abbreviation: AP, anterior–posterior.

FIGURE 3Electromonitoring may be of use during the surgery. If so desired by the surgeon,

paralyzing agentsmay not be used during surgery. The patient should not move at all duringthe surgery. A patient must not be paralyzed, yet he/she must be deeply anesthetized ifcontinuous electromyogram (EMG) and/or pedicle screw stimulation is to be utilized (above;probe on a tower attached to a percutaneously placed pedicle screw insulated by an outerinsulating plastic sleeve).

Pedicle-Targeting Techniques for Minimally Invasive Lumbar Fusions n 97

is perfectly prone and not tilted or shifted to one side, as this can jeopardize thefluoroscopic imaging. All of the Q2EKG leads, Foley catheter, etc., must be securelytaped to the side of the table so that there is no obstruction crossing the spinalregion in the standard AP and lateral planes. These are two crucial steps that arevery difficult to accomplish after the surgery has started, so they must be doneprior to patient preparation and draping. Patients who are allergic to Betadineshould be prepared using Hibiclens solution, and Ioban should not be used.Typically, an additional cutout of the spine cover drape should be done so thatalmost the entire back region is visible to the surgeon, not just the midline.

After a cutout is made, Ioban strips (3–4 inches) should be cut and placedalong the edges of the cover drape to seal the skin and sterile field region. A fullIoban drape should not be placed, because it will typically result in small piecesgetting caught in the guidance needles and/or tube systems, as well as fragmentsbeing deposited in the wound.

n OPTIMIZING THE IMAGE

An AP fluoroscopic image is obtained and the vertebrae being targeted should beseen in the middle of the intensifier screen (Fig. 4). Care should be taken that the

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FIGURE 4An AP fluoroscopic image should show the vertebrae being targeted in the

middle of the intensifier screen. The spinous process should be in the center of thevertebral body equidistant from a line drawn between two ipsilateral pedicles (line A).Abbreviation: AP, anterior–posterior.

98 n Spoonamore

correct level is identified, and a lateral image may also be required if there is anyuncertainty as to which level is visualized. The first step in fluoroscopic pedicletargeting is to obtain a perfect, en face view of the targeted vertebrae. Therefore, thesuperior endplate should be observed (Fig. 5). If the endplate does not appear tobe a flat, dark line, then the c-arm cantilever requires adjustment Q3so that it is theendplate is perfectly level. The second step requires the surgeon to ensure a truemidline view is obtained. The spinous process should be in the middle, and alsobe equidistant from the sides of the vertebral body and pedicles. The c-armover–under adjustment should be made to correct this if needed.

n NEEDLE LOCALIZATION

Q4After the targeted pedicle and vertebral body is perfectly visualized, a long,curved tonsil clamp can be used to make a marking on the skin over the pedicle(Fig. 6). The c-arm will typically have to be readjusted for each vertebral level,and then the markings can be made. A vertical line should be drawn connecting

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FIGURE 5A perfect en face view of the targeted vertebrae should be obtained. Therefore,

the superior endplate should be observed. If the endplate does not appear to be a flat,dark line, then the c-arm cantilever requires adjustment so that the endplate is perfectlylevel. A line connecting the two pedicles should intersect with the superior endplate of itsrespective vertebral body (line B). Abbreviation: AP, anterior–posterior.


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FIGURE 6After the targeted pedicle and vertebral body is perfectly visualized, a long,

curved tonsil clamp can be used to make a marking on the skin over the pedicles to beinstrumented.

FIGURE 7The A lines drawn on the AP view do no represent the incision lines. The next

step is to obtain a perfect bull’s-eye view of the targeted pedicle—this can be done byadjusting the c-arm over–under to the oblique view, usually 5˚ to 15˚ depending on thepedicle trajectory. A vertical line is drawn connecting the pedicles and is called line C, theincision line. Abbreviation: AP, anterior–posterior.

100 n Spoonamore

the pedicles, which is line A (step 3; Fig. 4). A horizontal line should also bedrawn connecting the pedicles, to be called line B (step 4; Fig. 5). Please note thatthese are not the incision lines, but are used as a reference when the guidancepins and wires are placed. The next step is to obtain a perfect bull’s-eye view ofthe targeted pedicle—this can be done by adjusting the c-arm over–under to theoblique view, usually 5˚ to 15˚ depending on the pedicle trajectory. A vertical lineis drawn connecting the pedicles and is called line C, the incision line (step 5;Fig. 7). The pedicle entry sites and trajectories for pedicle cannulation arechecked on a lateral view (Fig. 8).

AP FLUOROSCOPIC TECHNIQUE

n The AP technique involves using primarily the AP fluoroscopic image whenplacing and advancing the Jamshidi needle. The lateral view is also used, butexpert interpretive skills are needed to determine the appropriate placement ofthe Jamshidi needle and guide wires because only two views are being used toevaluate the position and the trajectory of a small needle in three dimensions.

n A small incision is made, usually 2 to 4cm, along line C. The incision is carriedsharply through the skin and subcutaneous tissue. Electrocautery may be used ifany bleeding is encountered. Typically, a Jamshidi type needle or trocar is thenplaced within the incision, in line with lines A and B (Fig. 9). Under fluoroscopicguidance using the AP view, the needle is directed obliquely (lateral to medial)and docked on the targeted pedicle. The ideal entry point of the pedicle is in themiddle; however, a slightly superolateral may be preferred, since the needle tip

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FIGURE 8The pedicle entry sites and trajectories for pedicle cannulation are checked on a

lateral view.


may tend to skive slightly inferior and medial as the needle is impacted.A modest tap with a small mallet is used to engage the Jamshidi needle intothe pedicle; frequent imaging is recommended at this time, especially forsurgeons with limited experience. The mallet is used to gently tap the Jamshidineedle and advance it further into the pedicle. Slight adjustments of the needletrajectory with reimaging will be required to ensure the needle is directed andadvanced perfectly within the pedicle.

n After the needle has been advanced approximately 1cm, a lateral fluoroscopicimage is obtained to verify the cranial–caudal trajectory of the needle. The lateralfluoroscopic image is obtained and the vertebrae being targeted should be seenin the middle of the intensifier screen. The superior endplate should beobserved. If the endplate does not appear to be a flat, dark line, then the c-armwig-wag requires adjustment so that the endplate is perfectly level.

n Careful analysis of the fluoroscopic imaging is required at this point of theoperation, and superior interpretive skills are required to accurately assessthe position of the needle and avoid neurologic complications. The Jamshidineedle should be observed to be perfectly within the desired pedicle, and shouldbe gently advanced until halfway into the pedicle. After that, the fluoroscopicimage should be changed back to the AP view. If the tip of the needle is seen tobe very close to (or more medial than) the medial wall of the pedicle, then theneedle is directed too medial. If the tip of the needle is seen to be close to thelateral wall and nonconvergent, then the needle is too lateral and not directedmedial enough. An oblique (bull’s-eye) view may also be utilized at this time tofurther verify needle position. Once the correct needle trajectory is confirmed,the needle should be advanced to one-third the depth of the vertebral body. Theneedle resistance should become noticeably less once the needle enters thevertebral body itself.

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FIGURE 9A Jamshidi type needle or trocar is then placed within the incision, in line with

lines A and B. Under fluoroscopic guidance using the anterior–posterior view, the needle isdirected obliquely (lateral to medial) and docked onto the targeted pedicle.

102 n Spoonamore

BULL’S-EYE TECHNIQUE

n Under fluoroscopic guidance using the oblique (bull’s-eye) view, the tip of theneedle is directed at the middle of the pedicle, as if you were aiming for a“bull’s-eye” on a dartboard. Generally, a small incision will already be madealong line C. The Jamshidi type needle or trocar is placed within the incision, inline with lines A and B. The ideal entry point of the pedicle is in the middle;however, a slightly superolateral may be preferred, since the needle tip may tendto skive slightly inferior and medial as the needle is impacted.

n A modest tap with a small mallet is used to engage the Jamshidi needle into thepedicle; frequent imaging is recommended at this time, especially for surgeonswith limited experience. After the needle is successfully docked into the pedicleentry point, the oblique bull’s-eye view should reveal that the needle appearsas a single dot within the circular bony walls of the pedicle seen on the image.The mallet is used to gently tap the Jamshidi needle and advance it further intothe pedicle. Slight adjustments of the needle trajectory with reimaging will berequired to ensure the needle is directed and advanced perfectly within thepedicle.

n After the needle has been advanced approximately 1 cm, a lateral fluoroscopicimage is obtained to verify the cranial–caudal trajectory of the needle. The lateralfluoroscopic image is obtained and the vertebrae being targeted should be seenin the middle of the intensifier screen. The superior endplate should beobserved. If the endplate does not appear to be a flat, dark line, then the c-armwig-wag requires adjustment so that the endplate is perfectly level. The needleshould be seen in the middle of the pedicle, directed perfectly in line with thepedicle.

n Small adjustments of the cranial–caudal trajectory can be made using this view,but care should be taken not to move the needle in any other plane. Once thecorrect needle trajectory is confirmed, the needle should be advanced to one-third the depth of the vertebral body. The needle resistance should becomenoticeably less once the needle enters the vertebral body itself. A return to theoblique bull’s-eye fluoroscopic view is recommended at this point to confirm

401402403404405406407408409410411412413414415416417418419420421422423424425426427428429430431432433434435436437438439440441442443444445446447448449450 FIGURE 10

Perfect pedicle cannulation and placement of the Jamshidi needle.


that a pedicle wall breach has not occurred, and then back to the lateral view forplacement of guide wire, dilators, tap, and screw.

Three possible scenarios of pedicle cannulation and placement of the Jamshidineedle (perfect, too medial, too lateral) are illustrated in Figures 10–12.

n GUIDE WIRE PLACEMENT

After the needle has been successfully advanced to one-third depth of the vertebralbody and confirmed to be in appropriate position, the sharp, inner stylet isremoved and a Kirschner guide wire is placed into the Jamshidi needle hole(Fig. 13). It is gently advanced to one-half to two-thirds the depth of the vertebral

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FIGURE 12Medial pedicle cannulation and placement of the Jamshidi needle—replacing of

the Jamshidi needle should be considered.

FIGURE 11Lateral pedicle cannulation and placement of the Jamshidi needle—replacing of

the Jamshidi needle should be considered.

104 n Spoonamore

body using only the lateral fluoroscopic view from this point forward. Great caremust be taken not to bend the guide wire when advancing it, and often a small tubedilator may be placed over it when advancing it and tapping it gently with amallet. After the guide wire is placed, the Jamshidi needle is removed. A careful,gentle twisting of the Jamshidi device is usually required to loosen it so that it canbe removed without pulling out the guide wire simultaneously.

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FIGURE 14Most percutaneous pedicle screw systems employ some type of dilator system

after the guide wire has been placed. The dilators typically fit over the guide wire and allowsequential expansion of the space.

FIGURE 13After the needle has been successfully advanced to a depth of one-third the

vertebral body and confirmed to be in appropriate position, the sharp, inner stylet isremoved and a Kirschner guide wire is placed into the Jamshidi needle hole.


BOOK SFT: Pedicle-Targeting Techniques for Minimally Invasive Lumbar

Fusions CHAPTER 7

TO: CORRESPONDING AUTHOR

AUTHOR QUERIES - TO BE ANSWERED BY THE AUTHOR

The following queries have arisen during the typesetting of your manuscript.Please answer these queries.

Q1 Au: Please spell out the acronym EMG.

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Minimally Invasive Surgery InInstrumented Lumbar Fusions

8 Donald W. Kucharzyk

n RATIONALE

Spine surgery techniques and technology have been evolving over the last severaldecades, with significant advancements in the surgical instruments used to thedevelopment of spinal instrumentation and hardware to improved intraoperativevisualization of the spine. These intraoperative advancements include fluoroscopy,image-guided fluoroscopy, high-resolution endoscopy, and improved fiber optics(1). As a result of these advancements, spine surgery has progressed from using ageneral surgical approach to using a minimally invasive and minimal accessapproach Q1This approach helps limit paraspinal muscle damage and dissection(2,3), limit intraoperative and postoperative blood loss, and reduce postoperativepain, and most importantly, it leads to a shorter hospitalization and quickerrecovery and rehabilitation. This translates into improved clinical and surgicaloutcomes, which is the test of any new technique and any advancing technology.

This concept has wide-ranging applications involving the spine, from itssimple introduction as a technique for discectomy (4–6), foraminotomy, andlaminotomy (7) to, most recently, its use in posterolateral fusions, interbodyfusions, and instrumented fusions.

As minimally invasive and minimal access surgery has evolved, so has thedevelopment of devices to provide access to the spine to perform these procedures.The first was the Medtronic MetRx Q2system (Fig. 1), which involved a tubularretraction system. This then evolved into X-Tube and now into the QuadrantSystems (Fig. 2), which provide an access channel to the spine for decompression,discectomy, interbody fusion, and instrumentation and fusion. Results have beenencouraging and have revealed positive outcomes in terms of clinical outcomes,reduced hospitalization, less blood loss, and more rapid return to work (8–11).Additional systems have emerged since then, including the DePuy Pipeline, theEndius ATAVI, the NuVasive MaXcess (Fig. 3), and the EBI VuePass (Fig. 4). Allthese allow the surgeon to access the spine to perform a decompression,laminectomy, facetectomy, foraminotomy, discectomy, interbody fusion, andinstrumentation.

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1011121314151617181920212223242526272829303132333435363738394041424344454647484950 Donald W. Kucharzyk The Orthopaedic, Pediatric & Spine Institute, Crown Point, Indiana, U.S.A.

107

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FIGURE 2Medtronic Sofomor-Danek Quadrant System for approach to the spine for not

only single but also multilevel fusions with instrumentation.

FIGURE 1Medtronic Sofomor-Danek MetRx system allows tubular access to the spine with

the ability to perform a discectomy and instrumented fusion.

108 n Kucharzyk

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FIGURE 4EBI VuePass System for minimally invasive access for instrumented fusions.

FIGURE 3NuVasive MaXcess system for surgical exposure of the spine.

Minimally Invasive Surgery In Instrumented Lumbar Fusions n 109

n APPROACH

An appropriate work-up for the patient preoperatively should include plainradiographs, anteroposterior and lateral, MRI scan, and also a CT scan. These testswill allow the surgeon proper planning and guide the access needed to address thepathology (Fig. 5 and Fig. 6).

The positioning of the patient can be over bolsters, on a Wilson orAndrews frame, or on a radiolucent table that will allow c-arm access andvisualization. The landmarks are then palpated and drawn out and the midlineis identified (Fig. 7). The ideal position for the skin incision is 1 to 3 cm fromthe midline and is dictated by whether a posterior lumbar interbody fusion(PLIF) (Fig. 8) or a transforaminal lumbar interbody fusion (TLIF) (Fig. 9)approach will be used to access the disc space. Skin incisions approximately3 cm are made and dissection carried down to the fascia. The fascia is thenincised slightly longer than the incision, and the natural plane between themultifidus and the longissimus muscle groups are developed (12). Under c-armvisualization, the initial guide pin is docked on the pars interarticularis, andprogressive dilators are inserted over each, sweeping from facet to facet todevelop the muscle plane (Figs. 10–12). The soft tissue dissector is then insertedand expanded and the length and depth of the retractor is determined (Fig. 13),and the radiolucent retractor EBI VuePass (Fig. 14) or the soft tissue retractorMedtronic Quadrant (Fig. 15) is inserted.

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FIGURE 5Plain radiograph revealing L5-S1 collapse with significant spondylosis and

endplate irregularities with posterior osteophytes.

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FIGURE 6MRI reveals a spondylotic HNP with reactive changes seen in the endplates and

vertebral body with collapse Q3of the disc and spondylosis with facet hypertrophy.

FIGURE 7Landmarks reveal the iliac crests, the midline, and skin incisions, which are

typically placed 2 to 4 cm from the midline centered over the level for fusion.


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FIGURE 8Skin incision, entry point, and angle of entry if a PLIF approach is desired.

Abbreviation: PLIF, posterior lumbar interbody fusion.

FIGURE 9Skin incision, entry point, and angle for approach if a TLIF is to be performed.

Abbreviation: TLIF, transforaminal lumbar interbody fusion.

112 n Kucharzyk

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FIGURE 10Placement of the guide wire docked on the pars interarticularis and located

either midline of a line drawn from pedicle to pedicle or slightly lateral, with the angledependent on the PLIF or TLIF approach. Abbreviations: PLIF, posterior lumbar interbodyfusion; TLIF, transforaminal lumbar interbody fusion.

FIGURE 11Dilators placed over the guide wire with sequential dilation of the soft tissue and

muscle.


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FIGURE 12Progressive dilators placed over each, with separation of the soft tissue and a

sweeping motion carried out from pedicle to pedicle to allow placement of the soft tissueretractor.

FIGURE 13EBI soft tissue retractor placed to maintain soft tissue distraction and allow

measurement of the depth and length of the radiolucent retractor that is placed throughthis retractor.

114 n Kucharzyk

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FIGURE 14Radiolucent retractors in place for bilateral access to the spine, with stabilizing

arms attached and angled for access to the spine for discectomy, interbody fusion, andinstrumentation.

FIGURE 15Quadrant system configuration for bilateral access to the spine for simultaneous

decompression of the spine and interbody fusion with instrumentation.


n DECOMPRESSION

Landmarks are identified and include the pars interarticularis and the facets(Fig. 16). A facetectomy is then carried out and a laminectomy can be performed toallow visualization of the dura and the exiting and traversing nerve roots and thedisc space (Fig. 17). The spinal column can be accessed by utilizing osteotomesdesigned for minimal access surgery. These osteotomes feature longer handles andallow continued visualization through the access retractors. Special rongeurs andkerrisons (Fig. 18) have been designed again to allow ease of access and continuedvisualization of the laminae and facets. Once access and the bone has beenremoved, a complete discectomy can be carried out, retractors are placed on thenerve roots, and a PLIF or TLIF approach per surgeon preference is carried out andan interbody fusion performed (Fig. 19 and Fig. 20).

n INSTRUMENTATION

With the aide of the c-arm, the landmarks are identified (Fig. 21), and using either adrill or a starter awl, the pedicles are entered and the position confirmed withc-arm X rays. The appropriate landmark for pedicle screw entrance is defined as aline drawn bisecting the superior and inferior articulating facets and crossing a linebisecting the transverse process. These lines and position are the same as thoseused during a standard open approach, and a more lateral entry point, if desired, isalso possible through this minimal access application.

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FIGURE 16Visualization through the VuePass system reveals the superior and inferior

articulating facets, the pars interarticularis, and the lateral gutter including the transverseprocesses.

116 n Kucharzyk

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FIGURE 17Following decompression, a guide wire is placed in the pedicle to the right with

the exposed dura at the top of the picture with a probe pointing to the dura, traversingnerve root and the exiting nerve root seen coming around the pedicle guide wire inferiorly. Q4

FIGURE 18Instrumentation for minimally invasive approach including (left ) pituitary

rongeurs, (top center ) nerve root retractor, (top right ) long handle knife, and (right )Kerrison rongeurs.


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FIGURE 19Placement of the interbody distractor for measurement and to maintain disc

height for decompression on the opposite side.

FIGURE 20Insertion of an interbody graft while maintaining the distractor on the opposite

side, with the nerve root retractor placed to protect but not retract the nerve roots.

118 n Kucharzyk

Guide wires are then inserted and confirmed on c-arm visualization (Fig. 21),and then the depths of the pedicles are determined and the pedicles taped with theappropriate size tap for the system used (Fig. 22). A neural monitoring probe isinserted and measurements recorded to determine if any violation of the pediclewall has occurred. Any monitoring system of choice can be used through thisapproach and confirms accuracy of pedicle screw placement. Also, direct palpationof the pedicle can also be carried out through this approach with special probesdesigned again for minimal access. The screws are then inserted (Fig. 23) andaligned for placement of the rods (Fig. 24 and Fig. 25). The rod lengths aremeasured and placed, locking nuts are applied, and the construct is completed.Final X rays are performed (Fig. 26–Fig. 28) and the incisions closed in a routinefashion (Fig. 29).

n POSTOPERATIVE MANAGEMENT

Patients are started on a Q5PCA postoperatively; this is discontinued on post-operative day 1 and oral pain medications are started. The patients are placed in an

Q6LSO brace for comfort and started on physical therapy immediately; the patient ismade to sit the afternoon or evening of surgery, and made to walk the morningafter. Patients are advanced to stair-climbing and lower-extremity exercises on thefirst postoperative day, and discharged 24 to 48 hours on average postop.

Rehabilitation is begun upon discharge with aqua physical therapy, andaquatic exercises are begun within the first week postop, progressing to formal

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FIGURE 21Visualization of the pedicles through the EBI VuePass system and placement of

the guide wires through the radiolucent tube on the opposite side; this reveals how well alllandmarks can be seen with this system, with the aid of c-arm and direct visualization.


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FIGURE 22Pedicles are taped with a size-specific tape over the guide wires previously

placed.

FIGURE 23Screws are inserted and the heads aligned for rod measurement and rod

insertion.

120 n Kucharzyk

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FIGURE 24Final placement of the rods and locking nuts: the placement of the bone graft is

relatively easy through this minimally invasive EBI VuePass approach, by simplyrepositioning the retractors in a sweeping movement laterally. Q7

FIGURE 25Placement of legacy instrumentation through the quadrant system, with bone

graft placed in the posterolateral gutter.


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FIGURE 26Final radiograph revealing the placement of the cortical interbody graft and final

screw and link placement utilizing EBI SpineLink 2.

FIGURE 27Final radiographs revealing placement of the rod instrumentation system with

biologic bioabsorbable interbody fusion device.

122 n Kucharzyk

801802803804805806807808809810811812813814815816817818819820821822823824825826827828829830831832833834835836837838839840841842843844845846847848849850 FIGURE 29

Final closure of wounds with skin incisions measuring 3.5 cm each.

FIGURE 28Final anteroposterior radiograph of placement of the hardware and interbody

implant, with placement of bone graft in the posterolateral gutter.


rehabilitation exercises based on the patient’s comfort level and daily assessmentby the spine physical therapist. Return to work status is assessed by functionalcapacity evaluations and response to work conditioning programs, which areinitiated usually within the first month or two postop.

n RESULTS

Results of the first 40 such surgeries (MIF) were recently reviewed and comparedwith a matched, randomized set of open instrumented single-level fusion (OF); itwas found that the operative time in the MIF group was longer by 30minutes.Blood loss was only 125 cc in the MIF group compared to 350 cc in the OF group, a65% reduction. Average hospitalization was only 36 hours in the MIF groupcompared to 80 hours in the OF group, a 55% reduction. Also, there was a 50%reduction in the duration of use of the PCA in postoperative pain management inthe MIF group as well as a 60% reduction in the amount of narcotic used duringthis period, compared to the OF group.

Rehabilitation results in the MIF group were ahead of the OF group at twoweeks, one month, and three months by on average 50%, and the MIF groupreturned to work 75% sooner than the OF group. All patients were followed-up18months; no evidence of any nonunion or pseudoarthrosis was seen with theinterbody fusions or in the posterolateral fusion masses.

n CONCLUSIONS

These results, although preliminary, do point to the positive effect that thisapproach, access, and technique has on the overall surgical and clinical outcomesof these patients. Q8Patient selection is very important in the use of this technique. Itallows the surgeon to utilize the open technique with only some minormodifications and with a much shorter learning curve for access to the spineand for instrumented fusion.

n REFERENCES

1. Seldomridge J, Phillips F. Minimally invasive spine surgery. Am J Orthop 2005; 34(5):224–232.

2. Kawaguchi Y, Matsui H, Tsuji H. Back muscle injury after posterior lumbar spinesurgery. A histologic and enzymatic analysis. Spine 1996; 21:941–944.

3. Sihvonen T, Herno A, Palijiarvi L, et al. Local denervation atrophy of paraspinalmuscles in postoperative failed back syndrome. Spine 1993; 18:575–581.

4. Foley KT, Smith MM. Microendoscopic discectomy. Tech Neurosurg 1997; 3:301–307.5. Kambin P, Gellman H. Percutaneous lateral discectomy of the lumbar spine:

a preliminary report. Clin Orthop 1983; 174:127–132.6. Matthews HH. Transforaminal endoscopic microdiscectomy. Neurosurg Clin North Am

1996; 7:59–63.7. Khoo LT, Fessler RG. Microendoscopic decompressive laminectomy for the treatment of

lumbar stenosis. Neurosurgery 2002; 51(Suppl. 2):146–154.8. Foley KT, Smith MM, Rampersaud YR. Microendoscopic discectomy. In: Schmidek HH,

ed. Operative Neurosurgical Techniques: Indications, Methods, and Results, 4th edn.Philadelphia, PA: WB Sanders, 2000.

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9. Hilton DL. Microdiscectomy with minimally invasive tubular retractor. In: Perez-Cruet,Fessler RG, eds. Outpatient Spinal Surgery. St. Louis, MO: Quality Medical Publishing,Inc, 2002, pp. 159–170.

10. Foley KT, Lefkowitz MA. Advances in minimally invasive spine surgery. ClinNeurosurg 2002; 49:499–517.

11. Foley KT, Holly LT, Schwender JD. Minimally invasive lumbar fusion. Spine 2003; 28:S26–S35.

12. Wiltse LL. The paraspinal sacrospinalis splitting approach to the lumbar spine. ClinOrthop 1973; 91:48–57.

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Minimally Invasive TransforaminalLumbar Interbody Fusion

9 Mark R. Grubb

n INTRODUCTION

An increasingly popular method for lumbar arthrodesis is transforaminal lumbarinterbody fusion (TLIF) (1–5). In a manner similar to posterior lumbar interbodyfusion (PLIF) (6,7), TLIF provides for a 360˚ spinal fusion. Traditional posterolateralonlay techniques have been reported to have lower arthrodesis rates thaninterbody lumbar fusion techniques (8–12).

TLIF and PLIF offer a number of potential benefits over conventionalposterolateral intertransverse arthrodesis, including increased fusion surface area,copious fusion blood supply via cancellous vertebral body bone, complete accessfor medial and lateral decompression, and restoration of intervertebral body height(8). Unfortunately, with PLIF, retraction and manipulation of the neural elementsare required for disc space access. This has linked PLIF with a significant rate ofneurologic injury (13–17).

A more lateral approach, TLIF provides access to the disc space without theneed for significant retraction of the nerve roots or thecal sac. TLIF is a unilateralprocedure and therefore avoids the need for bilateral dissection within the epiduralspace. TLIF also makes revision surgeries less challenging, as there is less need tomobilize the nerve roots away from scar tissue. Finally, important midline-supporting bony and ligamentous structures are preserved with TLIF.

Conventional posterior lumbar surgery, regardless of the fusion technique, isassociated with significant soft tissue morbidity that can adversely affect patientoutcomes (18–23). Reduction in the iatrogenic soft tissue injury that occurs withmuscle stripping and retraction during routine spinal exposure is the rationale forminimally invasive posterior lumbar fusion techniques (24–26). In this chapter, wewill outline the indications, surgical technique, results, and complications ofperforming the TLIF procedure using a minimally invasive approach.

Iatrogenic soft tissue and muscle injury that occurs during routine surgicalexposure accounts for most of the significant morbidity of open instrumentedlumbar fusion procedures. Well documented in the medical literature are thedeleterious effects of extensive muscle stripping and retraction (18–23,27). Thesenegative effects of lumbar surgery occur so commonly that the term “fusiondisease” has been used to describe their occurrence. The effects of retractor bladepressure on the paraspinous muscles during surgery have been evaluated byKawaguchi et al. (18,19) and Styf and Willen (23). They found that the elevated

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Mark R. Grubb Department of Orthopaedic Surgery, Northeast Ohio Spine Center, NortheasternOhio Universities College of Medicine, Canton, Ohio, U.S.A.

127

serum level of creatine phosphokinase MM isoenzyme, a direct marker of muscleinjury, is related to the retraction duration and pressure. The beneficial effects ofsurgery can be negated by the long-term problems of this iatrogenic muscle injury.Rantanen et al. (21) concluded that patients who had poor outcomes after lumbarsurgery were more likely to have persistent pathologic changes in theirparaspinous muscles. It has been shown that patients who had undergone fusionprocedures had significantly weaker trunk muscles than discectomy patients (20).

Minimally invasive spinal surgery with a less traumatic approach aims toachieve the same objectives as open surgery. However, reducing the approach-related morbidity must be accomplished without reducing procedure efficacy.

n SURGICAL TECHNIQUE

Following the induction of general endotracheal anesthesia, the patients werepositioned prone on a Jackson (OSI) table. The patients were prepped and drapedin the usual sterile manner. Lateral and anteroposterior (AP) c-arm fluoroscopicimages were obtained. Using fluoroscopic guidance and a 18-gauge spinal needle,a 2.5 cm incision was made, centered on the interspace of interest approximately5.0 cm lateral to the midline. The TLIF approach was carried out on the sideipsilateral to the worst radiculopathy. Contralateral Pathfinder (Abbott Spine,Austin, TX) pedicle screws and rod were placed through a separate 2.5 cm, mirror-image incision centered over the interspace. Through this incision, one can distractthe interspace using the Pathfinder distracter, and then provisionally tighten thescrew–rod connections in the distracted position. On the TLIF side, electrocauterywas used to incise the fascia, after which serial dilators were used to create amuscle-sparing surgical corridor as originally described for the microendoscopicdiscectomy procedure (28–31). An appropriate-length 22 Q1-diameter METRx(Medtronic Sofamor Danek, Memphis, TN) tubular retractor was docked on thefacet joint complex (Fig. 1). The remainder of the procedure can be performed with

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FIGURE 1Dilation up to 22mm using serial dilators, approximately 4 to 5 cm from midline

with oblique orientation.

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128 n Grubb

the operative microscope or with loupe magnification, depending on the surgeon’spreference. A total facetectomy was carried out using a high-speed drill. Theremoved bone was denuded of all soft tissue, morselized, and then later used forinterbody graft material. The lateral margin of the ligamentum flavum wasresected to expose the ipsilateral exiting and traversing nerve roots. Typically, onlythe most lateral margin of the traversing root was exposed so that it could beidentified, protected, and decompressed as necessary. If needed, though, thetubular retractor could be wanded (angled) medially so that a more extensivedecompression could be carried out (including decompression of central canalstenosis; Fig. 2). A discectomy was next performed through the ipsilateral tubularretractor. Epidural veins were controlled with bipolar cautery; thrombin-soakedGelfoam was used for additional hemostasis, as necessary. At this point, distractionwas performed, which allowed better access to the interspace, improvedvisualization of the annulus, and further protected the nerve roots. Intervertebraldistraction was performed in a bilateral and simultaneous manner by using theinterbody paddles inserted into the disc space through the ipsilateral METRx tubeand applying the Pathfinder distracter to the contralateral pedicle screws (Fig. 3).This distraction was maintained via provisional tightening of the contralateralPathfinder construct. However, if anterolisthesis was present and reduction waswarranted, this could be accomplished using the Pathfinder reduction instruments(Fig. 4). The distracted position allowed improved access to the contralateral sideof the interspace for completing the discectomy and preparing the endplates forfusion. Typically, cartilaginous material was removed from the endplates, but theircortical portions were retained. Structural allograft bone, cages, bone morphoge-netic protein (BMP), various bone graft expanders, and/or local autologous bonegraft can be placed into the interspace depending on surgeon preference. The localautograft (combined with a BMP-soaked collagen sponge or other bone graftexpander) was placed anteriorly and contralateral to the annulotomy within theinterbody space (Fig. 5). Additional autograft bone was placed into the interspace

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FIGURE 2View through tubular retractor. The port has been wanded to allow a more

extensive decompression of the thecal sac.

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Minimally Invasive Transforaminal Lumbar Interbody Fusion n 129

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FIGURE 3(A) Distraction using intervertebral paddle distractor (in hand ) and Pathfinder

distractor applied to contralateral pedicle screws. (B) Lateral fluoroscopic view of paddledistractor inserted into disc space and Pathfinder distractor placed on contralateral pediclescrews: predistraction. (C) Lateral fluoroscopic view following simultaneous application ofPathfinder distractor and rotation of intradiscal paddle distractor. Note the significantchange in disc space height.

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130 n Grubb

after insertion of the structural graft, if space allowed. Once the interbody fusionhad been carried out, the contralateral pedicle screw construct was compressedusing the Pathfinder compressor. The tubular retractor was removed and anipsilateral Pathfinder pedicle screw–rod construct was placed through the sameincision. Bilateral compression was applied to the construct prior to finaltightening, providing compression of the bone graft within the middle columnand recreating lordosis.

n CLINICAL STUDY

A nonrandomized, prospective study of patients treated with a uniform surgicaltechnique by a single surgeon was conducted. The patient group consisted of 31patients, with a mean age of 54.2 yearss. All patients were taking narcoticmedications prior to surgery. Slightly over half of the patients were workingpreoperatively.

All interbody procedures were performed via a unilateral TLIF procedure.The TLIF component was performed through a 22mm tubular retractor.

Exposure of the disc space through the foramen followed facetectomy.Subtotal discectomy allowed for the interbody cage and bone graft to be placed inan oblique fashion. Bilateral percutaneous pedicle screw instrumentation was thencompleted. Percutaneous pedicle screw instrumentation was accomplished underelectromyogram and fluoroscopic control. Patients were assessed radiographicallyand clinically preoperatively and at 3, 6, 12, and 24 months.

All surgeries were for level 1 disease, primarily spondylolisthesis. All thedevices were implanted via unilateral TLIF. The average surgical data are as follows:estimated blood loss, 125 cc; surgical time, 211minutes; hospital stay, 2.2 days. Therewere five complications: one cerebrospinal fluid leak (unrelated to pedicle screwinsertion), one ileus, one right leg numbness (resolved), one superficialwound infection, and one interbody graft retropulsion (required reoperation).

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FIGURE 4Spondylolisthesis-reduction instrumentation.

Q3


MeanOswestry scoreswere: preop, 31.2; 12months, 19.9; 24months, 18.1.Mean backpain scoreswere: preop, 8.8; 12months, 3.2; 24months, 2.8. Two-thirds of thepatientswereworking at two years postop; 6 of 31 patientswere retired at two years postop; 4of 31 had disability at two years; 96.8% patients demonstrated rigid fusion on

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FIGURE 5(A) Lateral fluoroscopic image showing placement of implant spacer within the

disc space. (B) Placement of morselized autograft into disc space via a funnel.

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132 n Grubb

flexion–extension films at two years postop. The reoperation rate was 3%. At24 months, 19% of patients were taking narcotic medications. Ninety-seven percentof patients were satisfied with the outcome of the surgery.

n DISCUSSION

In this chapter, we have discussed the minimally invasive TLIF (MITLIF)procedure. Specialized instruments, a tubular retractor system, and thePathfinder system have made the TLIF procedure feasible. Serial dilation of theparaspinous operative corridor allows the surgeon to dissect through the muscleand fascia with minimal tissue trauma. Percutaneous pedicle screws can be placedthrough the same incisions.

The creation of a working channel between the muscle fibers permits accessto the bony anatomy without the need for muscle stripping, unlike the open TLIFprocedure. As a result, the estimated blood loss in our experience averaged only125mL, including pedicle screw placement. Blood loss during conventionallumbar fusion surgery can be quite significant; in fact, patients commonly donateautologous blood preoperatively or a cell saver is used during the surgery. None ofthe our patients required a blood transfusion. Compared with similar openprocedures, patients had less pain following the MITLIF. Narcotic use wassignificantly reduced postoperatively. In addition, the average hospital stay wasrelatively short: 2.2 days.

We have outlined the many potential benefits of the MITLIF procedure.MITLIF does have its drawbacks and limitations. The learning curve that must besurmounted before technical proficiency can be achieved is not insignificant.Standard landmarks that are visualized during open procedures may beunexposed during minimally invasive procedures, which could lead to anatomicdisorientation. MITLIF is more technically demanding than open TLIF. This is dueto a number of factors, including working in a smaller area and the need for longerand bayoneted surgical instruments. Additionally, placement of percutaneouspedicle screws requires the surgeon to be able to accurately interpret AP and lateralfluoroscopic images to safely insert these devices. Screw misplacement can beminimized by attention to anatomic detail. Use of intraoperative electromyographyis also helpful in avoiding this potential complication. Image guidance systems willlikely further reduce screw placement error.

When severe neural compression is present on the side contralateral to theTLIF approach, consideration should be given to direct decompression of theneural structures on that side. This can be accomplished by inserting a tubularretractor through the contralateral incision prior to contralateral percutaneouspedicle screw placement.

n CONCLUSION

MITLIF offers a number of potential advantages over traditional open lumbarfusion techniques. MITLIF is a technically demanding procedure. It is a feasibleoption for many patients and can be performed with a relatively lowcomplication rate.

n REFERENCES

1. Harms JG, Jeszenszky D. The unilateral transforaminal approach for posterior lumbarinterbody fusion. Orthop Traumatol 1998; 6:88–99.

2. Harms JG, Rollinger H. A one-stage procedure in operative treatment of spondylolisth-esis: dorsal traction-reposition and anterior fusion. Z Orthop Ihre Grenzeb 1982; 120:343–437.

3. Lowe TG, Tahernia AD, O’Brien MF, et al. Unilateral transforaminal posterior lumbarinterbody fusion (TLIF): indications, technique, and 2-year results. J Spinal Disord 2002;15:31–38.

4. Moskowitz A. Transforaminal lumbar interbody fusion. Orthop Clin North Am 2002;33:359–366.


6. Cloward RB. Spondylolisthesis: treatment by laminectomy and posterior interbodyfusion. Clin Orthop Relat Res 1981; 154:74–82.

7. Cloward RB. The treatment of ruptured lumbar intervertebral discs by vertebral bodyfusion. I. Indications, operative technique, after care. J Neurosurg 1953; 10:154–168.

8. Hacker RJ: Comparison of interbody fusion approaches for disabling low back pain.Spine 1997; 22:660–666.

9. Fraser RD. Interbody, posterior, and combined lumbar fusions. Spine 1995; 20:8167–8177.

10. Branch CL. The case for posterior lumbar interbody fusion. Clin Neurosurg 2000; 47:252–267.

11. Branch CL, Branch CL Jr. Posterior lumbar interbody fusion: the keystone technique. In:Lin PM, Gill K, eds. Lumbar Interbody Fusion. Rockville, MD: Aspen, 1989, pp. 211–219.

12. McLaughlin MR, Haid RW, Rodts GE, et al. Posterior lumbar interbody fusion:indications, techniques, and results. Clin Neurosurg 2000; 47:514–527.

13. Fraser RD. Interbody, posterior, and combined lumbar fusions. Spine 1995; 20:S167–S177.

14. Elias WJ, Simmons NE, Kaptain GJ, Chadduck JB, Whitehill R. Complications ofposterior lumbar interbody fusion when using a titanium-threaded cage device. JNeurosurg 2000; 93(Suppl. 1):45–52.

15. Ray CD. Threaded titanium cages for lumbar interbody fusions. Spine 1997; 22:667–680.16. Stonecipher T, Wright S. Posterior lumbar interbody fusion with facet-screw fixation.

Spine 1989; 14:468–471.17. Lin PM. Posterior lumbar interbody fusion technique: complications and pitfalls. Clin

Orthop Relat Res 1985; 193:90–102.18. Kawaguchi Y, Matsui H, Tsuji H. Back muscle injury after posterior lumbar spine

surgery. A histologic and enzymatic analysis. Spine 1996; 21:941–944.19. Kawaguchi Y, Matsui H, Tsuji H. Back muscle injury after posterior lumbar spine

surgery. Part 2: histologic and histochemical analyses in humans. Spine 1994; 19:2598–2602.

20. Mayer TG, Vanharanta H, Gatchel RJ. Comparison of CT scan muscle measurementsand isokinetic trunk strength in postoperative patients. Spine 1989; 14:33–36.

21. Rantanen J, Hurme M, Falck B, et al. The lumbar multifidus muscle five years aftersurgery for a lumbar intervertebral disc herniation. Spine 1993; 18:568–574.

22. Sihvonen T, Herno A, Paljiarvi L, et al. Local denervation atrophy of paraspinal musclesin postoperative failed back syndrome. Spine 1993; 18:575–581.

23. Styf JR, Willen J. The effects of external compression by three different retractors onpressure in the erector spine muscles during and after posterior lumbar spine surgeryin humans. Spine 1998; 23:354–358.

24. Foley KT, Lefkowitz MA. Advances in minimally invasive spine surgery. ClinNeurosurg 2002; 49:499–517.

25. Khoo LT, Palmer S, Laich DT, Fessler RG. Minimally invasive percutaneous posteriorlumbar interbody fusion. Neurosurgery 2002; 51:8166–8181.

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26. Foley KT, Holly LT, Schwender JD. Minimally invasive lumbar fusion. Spine 2003; 28:S26–S35.

27. Gejo R, Matsui H, Kawaguchi Y, et al. Serial changes in trunk muscle performance afterposterior lumbar surgery. Spine 1999; 24:1023–1028.

28. Foley KT, Smith MM. Microendoscopic discectomy. Techn Neurosurg 1997; 3:301–307.29. Perez-Cruet MJ, Foley KT, Isaacs RE, Rice-Wyllie L, Wellington R, Smith MM, et al.

Microendoscopic lumbar discectomy: technical note. Neurosurgery 2002; 51:S129–S136.30. Fessler RG, Khoo LT. Minimally invasive cervical microendoscopic foraminotomy: an

initial clinical experience. Neurosurgery 2002; 51:S37–S45.31. Guiot BH, Khoo LT, Fessler RG. A minimally invasive technique for decompression of

the lumbar spine. Spine 2002; 27:432–438.

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Lumbar Interbody Fusion: Techniques andIndications Adopted for MinimallyInvasive Surgery

10 Robert F. McLain

n INTRODUCTION

Surgeons routinely use lumbar spinal fusion to treat a variety of pathologicalconditions, but nonunion rates, instrumentation failure, and the inability to restoresagittal balance associated with posterior fusions still compromise outcomesin some patients (1–5). Some of the concerns are exposure related, caused by theextensive muscle dissection needed for a traditional open, midline, lumbar surgery.The stripping of muscle from bone may lead to excessive blood loss, fattydegeneration of the paraspinal muscles, and more pain. In this chapter, we reviewthe current indications for and techniques of posterior lumbar interbody fusion(PLIF) and transforaminal lumbar interbody fusion (TLIF), and how these methodscan be adopted for the minimally invasive approach.

n POSTERIOR LUMBAR INTERBODY FUSION

PLIF is an important alternative to traditional posterolateral fusion, providingsimultaneous grafting and stabilization of both anterior and posterior structuralcolumns, and a wide neural decompression, all performed through a single,midline, posterior incision. The PLIF procedure—fusion of the spinal segment byplacing graft material into the prepared intervertebral space through a poster-olateral annulotomy—has been around for many years, but has only recentlybegun to enjoy widespread popularity.

n TRANSFORAMINAL LUMBAR INTERBODY FUSION

TLIF, a modification of the PLIF procedure, has evolved because of its potential topreserve normal soft tissue structures and utility as a unilateral approach to theintervertebral space. The TLIF procedure has the potential to reduce the incidenceof nerve root injury and dural tear associated with the traditional PLIF approach.Surgeons seeking ways to further reduce iatrogenic soft tissue trauma and nerveroot injury have developed a variety of modifications and tools for minimallyinvasive approaches to PLIF and TLIF surgery.

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Robert F. McLain Cleveland Clinic Lerner College of Medicine, Cleveland Clinic Spine Institute,The Cleveland Clinic Foundation, Cleveland, Ohio, U.S.A.

137

n SURGICAL GOALS OF PLIF AND TLIF

PLIF and TLIF procedures are technically demanding. Properly executed, theyprovide anterior column stability in axial loading, augment the fusion potential byincreasing graft contact area, restore disc-space height and sagittal alignment,restore foraminal volume, and place bone graft in the most physiologicallyfavorable environment—under compression, between two broad plates of well-vascularized bone.

The goals of this technique are the following:

1. Solid interbody fusion2. Restoration of normal intersegmental alignment3. Complete decompression of the neural elements4. Using a single posterior approach for goals 1 to 3.

n HISTORY

In 1936, Mercer (6) theorized that the ideal operation for the spine would be aninterbody fusion, but he conceded that the procedure was impossible to perform atthat time given the limitations of anesthesia and existing equipment. Jaslowreported the first successful PLIF in 1946 (7), when he placed a bone peg in thelumbar interbody space following discectomy, and augmented this interbody graftwith autogenous bone chips. Since then, many others have recognized the value ofthe PLIF procedure.

Cloward popularized the technique in the 1950s, proposing interbody fusionas a first-line strategy for ruptured lumbar discs (8). Lin et al. recommendedtechnical advances (9): preserving the posterior elements of the motion segment tomaintain stability, performing a total discectomy so that a large area of bonycontact was obtained, filling the prepared interspace with a combination of corticaland cancellous bone to reproduce the biomechanical behavior of Robinson’stricortical anterior cervical graft, and partially decorticating the weight-bearingportion of the vertebral endplates.

Brantigan and Steffee presented their results with a carbon-fiber PLIF cageand autograft bone in 1993, and noted a marked improvement in fusion ratecompared to ethylene oxide–sterilized allograft bone (10,11).

Problems commonly encountered in early series, including nerve root injury,graft displacement, and nonunion, have been solved to a great degree withimprovements in spinal instrumentation and interbody grafting techniques, and abetter understanding of the surgical exposure required for safe access to theintervertebral space (12–15).

While the PLIF approach has evolved over the past six decades, the TLIF wasinitially described by Harms et al. in 1996 as a modification of the PLIF (12,13).Therefore, TLIF is also a viable alternative to anteroposterior circumferential andanterior lumbar interbody fusion. The TLIF approach provides access to theintervertebral space through the far lateral aspect of the intervertebral foramen. Itoffers good exposure with decreased risk during revision surgery where scar tissuemakes PLIF very difficult. Although the PLIF approach permits good posteriordecompression, it can be difficult to remove sufficient amounts of disc tissuethrough a unilateral TLIF. Moreover, it can be very hard to sufficiently mobilize thesegment if there is a slip or segmental deformity. The TLIF can be carried out

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138 n McLain

unilaterally or bilaterally through a laminectomy with an inferior facetectomy anddiscectomy. The arthrodesis is completed with pedicle screw fixation and insertionof titanium, polyether-ether-ketone (PEEK), or carbon-fiber cages packed withautologous bone, another bone graft substitute, or BMP Q1.

Clinical studies have reported excellent outcomes, with few complications(16–19). Few clinical problems, such as cerebrospinal fluid leaks, transientneurological complications, and minor wound infections, have been described.Fusion rates in patients have been reported to be as high as 74% to 93% Q2(16–19). Ithas been recognized that TLIF may lessen the risk of injury to neural elements andmay minimize the impact of destabilizing midline decompressive procedures suchas PLIF (16–19). It has ideally lent itself for application in minimally invasiveapproaches to the spine by utilizing the paraspinal Wiltse muscle-splittingapproach. It has become a safe technique for interbody support, with a comparableclinical outcome to PLIF (20–22).

n INDICATIONS/CONTRAINDICATIONS

The PLIF and TLIF procedures may be applied at a single spinal segment,repeatedly in adjacent segments, or at one level in a multilevel instrumentationwhere the need for intersegmental distraction and fusion is limited to a single level.The indications for PLIF and TLIF include severe degenerative disease and grossspinal instability, discogenic low-back pain, segmental instability, saggitalimbalance, loss of disc-space height with foraminal encroachment, and increasedrisks of pseudarthrosis. Chronic low-back pain is not an indication in and of itself,unless one of these other conditions can be shown to be the cause.

The PLIF and TLIF procedure is primarily indicated for treatment of thefollowing:

n Discogenic back pain: Severe and intractable back pain generated by nerveendings in and around the degenerating disc, and by facet arthropathy andinstability resulting from disc degeneration.

n Spondylolisthesis: Reduction of deformity often requires intersegmental distrac-tion. This results in a loss of anterior load-sharing ability, putting screws at riskof failure unless anterior column support is restored.

n Pseudoarthrosis: A challenging problem, the posterior intertransverse bone graftbed is compromised by scar and fibrous tissue from the previous fusion attempt.Excessive resection of the facets may have occurred. The intervertebral spacemay be the best chance for achieving a viable fusion.

n Recurrent disc herniation: Recurrent herniation in a patient with associated axialback pain may be best managed by a complete discectomy and PLIF or TLIF.

n Transition syndrome: Adjacent level instability often features marked disc-spacecollapse and disc disruption. Resulting stenosis and foraminal encroachmentwarrant wide decompression in addition to segmental fusion.

n Postlaminectomy instability: Once the lamina and ligamentous supports of thediseased segment have been removed, progressive instability and pain are likely.Posterolateral fusion is less reliable when so much posterior bone has beenremoved, and PLIF greatly increases the chances for successful fusion.

n Degenerative scoliosis: Complex multiplane deformities associated with degenera-tive disease or idiopathic scoliosis may be better corrected by PLIF at appropriatelevels. Foraminal height can be restored, translational slips and segmental

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Lumbar Interbody Fusion: Techniques and Indications n 139

angulation corrected, and the fusion rate among these challenging patientsmay begreatly improved when critical levels are augmented by PLIF or TLIF.

Contraindications to PLIF and TLIF include the following:

n Severe epidural fibrosis precludes safe exposure of the disc interspace duringPLIF. Unless the nerve roots and thecal sack can be adequately mobilized, graftplacement will be either impossible or dangerous to the neural structures.

n Epidural fibrosis may also be a relative contraindication to the TLIF approach.Stenosis in the central canal and in the entry zone of the lateral recess may still bedifficult to dissect. Therefore, care is warranted when mobilizing the exiting andtraversing nerve root.

n Severe osteoporosis not only compromises the internal fixation, but also maylead to excessive bleeding once the endplate is disrupted. Subsidence afterimplant placement can cause pain, deformity, and a poor result.

Both operations are traditionally limited to the middle and lower lumbarspine, because the conus medullaris ends at L1 and is at risk with excessiveretraction. PLIF can be safely accomplished up into the thoracic spine, however, byobserving a meticulous technique.

n ANATOMY AND BIOMECHANICAL PRINCIPLES

Safe and successful PLIF and TLIF depend on proper placement of the interbodyspacer without injury to the neural structures. This can be best accomplished if thesurgeon identifies and creates a “safe zone” over the intervertebral disc withinwhich to work (Fig. 1 Q3). The “safe zone” consists of the space between the medialborder of the exiting nerve root above and laterally, the lateral border of thetraversing root or thecal sack medially, and the full height of the disc spacesuperior to the pedicle, within the neural foramen. This zone is located withinthe axilla between the exiting and traversing nerve roots. The medial wall of theinferior pedicle provides a consistent landmark in both virgin and revision cases,and the shoulder of the traversing nerve is found just medial to this.

To expose the “safe zone” for PLIF or TLIF, a wide laminectomy isperformed. A bilateral (PLIF) or unilateral (TLIF) Gill decompression provides thewidest exposure and insures decompression of the nerves. After removing theinferior and superior facets, the medial walls of the superior and inferior pediclesare identified. The exiting nerve traverses around the base of the superior pedicleinto the foramen and across the face of the disc. After facetectomy, the nerve rootis mobilized cranially to widen the safe zone cranially and laterally. Once thesestructures are identified and protected, the posterolateral expanse of the annulus isin full view and easily incised.

The biomechanical goal of PLIF or TLIF is to provide anterior columnsupport while fusion takes place. The interbody fusion cage restores disc-spaceheight at the same time, and, thereby, restores sagittal alignment of the lowerlumbar segments. Properly completed, the PLIF or TLIF should restore the L4superior endplate to an alignment parallel to the floor, when standing, and reverseany focal kyphosis that has occurred due to disc-space collapse. The interbodyspacer shares axial loads transmitted through the spinal column, and greatlyreduces bending moments experienced by the dorsal pedicle screw construct.Without the interbody device, disc-space correction can only be accomplished by

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140 n McLain

distracting the vertebral bodies using the pedicle screws themselves, making thepedicle screw construct a load-bearing device. This places excessive cantileverbending forces on the screws, resulting in an unacceptable rate of screw failure,either through bending, breakage, or loosening.

n PREOPERATIVE PLANNING

Weight-bearing radiographs with flexion and extension views demonstrate disc-space narrowing, and reveal any spondylolisthesis, fixed or mobile, that may needto be addressed during the PLIF or TLIF. Discography is indicated in patients withmultilevel degenerative changes to confirm the probable pain generator. A positivediscogram must recreate the patient’s principal pain at the appropriate level(concordant pain). Injection at adjacent levels should produce no pain. Patientswith inappropriate responses are poor candidates for surgery.

Prior to revision surgery, an MRI to determine the extent and density ofepidural scarring resulting from the previous procedures should be obtained.A heavy, thick scar around facets and fusion mass may preclude a PLIF procedure. ATLIF may be more appropriate to deal with epidural scar tissue in the lateral recess.

Dexa scanning is warranted for older patients. If osteoporosis is present,pedicle screws may need to be augmented with bone cement.

n SURGICAL TECHNIQUES

The surgical technique can be divided into four stages.

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FIGURE 1Surgical anatomy of the disc space and neural foraminae create a “safe zone”

within which to work. This safe zone is formed by the medial border of the Q3exiting nerveroot above and laterally, lateral border of the traversing root or thecal sack medially, andthe full height of the disc space superior to the pedicle, within the neural foramen. The safezone is located within the axilla between the exiting and traversing roots. The medial wallof the inferior pedicle provides a consistent landmark in virgin and revision cases, and theshoulder of the traversing nerve is just medial to this.


EXPOSURE, DECOMPRESSION, AND MOBILIZATIONThe exposure, decompression, and mobilization of neural structures are necessarybefore the surgeon can gain access to the disc space. Wide decompression allowsthe surgeon to visualize and mobilize the individual spinal nerves, creating a “safeworking zone.”

INSTRUMENTATIONPosterior segmental instrumentation allows the surgeon to distract the disc space,hold the disc space open for graft placement, and reduce existing deformity duringinterbody fusion. Pedicle screws are the only implant that can hold reductionacross a single motion segment after laminectomy and decompression have beencompleted.

ANTERIOR COLUMN RECONSTRUCTIONAnterior reconstruction and grafting are carried out to restore disc height andcorrect deformity, as well as augment the fusion process. This is the actual PLIF orTLIF procedure—the delivery of a prosthesis to reconstruct the anterior spinalcolumn and create fusion.

SECONDARY FUSION AND FINAL INSPECTIONFinally, the surgeon compresses and locks the posterior instrumentation, performsa posterolateral fusion, if so inclined, and closes the wound.

n SURGICAL TECHNIQUES: OPEN PLIF AND TLIF

EXPOSURE, DECOMPRESSION, AND MOBILIZATIONAny operative frame that reduces intra-abdominal pressure can be used for thisprocedure, but an Andrews or knee-chest frame is preferred for lower lumbarlevels. The knee-chest position reduces lumbar lordosis and widely opens thelumbar interspaces for easier decompression prior to instrumentation (Fig. 2). If akneeling frame is used, however, the surgeon must pay particular attention tosagittal balance when completing the instrumentation, and restore proper lordosisby compressing the segment posteriorly. If the surgeon wishes to use fluoroscopyduring pedicle screw placement, a radiolucent frame may be used instead, with thelower extremities slightly flexed and held in a sling. The use of a cell-salvage bloodrecovery system limits the need for transfusion.

After a midline incision is performed, the pars intra-articularis at the fusionlevel must be identified and dissected free from the soft tissues. Take care topreserve the interspinous ligament and facet joints of the superior segment toprevent adjacent-level degeneration or instability. Alternatively, the same surgicalprocedure can be performed through a midline mini-open incision with the use ofa minimally invasive surgery (MIS) retractor system.

The laminectomy extends from the origin to the insertion of the ligamentumflavum. The spinous processes and lamina are removed to expose the canal (Fig. 3).If a single level procedure is planned, try to preserve the upper one-half of thelamina above the PLIF level. This minimizes disruption of uninvolved structures. Ifwider exposure is necessary, remove the entire lamina of the superior vertebra bycreating an iatrogenic “pars defect” through the superior lamina, using a chisel,

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Kerrison rongeurs, or drill. This technique disarticulates the inferior facet, and thelaminar arch and facets can then be removed in one piece, exposing the superiorfacet of the vertebra below. Place a guide under the pars to protect the underlyingdura and nerve roots.

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FIGURE 2The Andrews frame allows the patient to be positioned in a knee-chest position,

opening the lower lumbar lamina and facilitating the decompression, while leaving theabdomen free and reducing intra-abdominal pressure and blood loss.

FIGURE 3In both PLIF (A) and TLIF (B), complete resection of the pars and adjacent facets

insures nerve root decompression, provides wide access to the interspace, and permitsPLIF or TLIF cage or spacer placement with the greatest safety to the nerve root andthecal sac. The red dotted line indicates the extent of bony resection. Abbreviations: PLIF,posterior lumbar interbody fusion; TLIF, transforaminal lumbar interbody fusion.


The “safe zone” is created by removing the entire inferior and superior facets,exposing the medial border of the exiting nerve root, the lateral border of thetraversing root or thecal sack, and the full height of the disc space above theinferior pedicle, within the neural foramen (Fig. 4). Once the medial pedicle wall isidentified, the shoulder of the traversing nerve is gently mobilized toward themidline. Minimal dissection is carried out over the floor of the canal to minimizeepidural bleeding. Thrombin-soaked Gelfoam (Pfizer, New York) and bipolarelectrocautery are employed to control bleeding (Fig. 4).

After performing a wide decompression and facetectomy, the superior andinferior pedicles are fully visualized. Using a Woodson elevator or nerve probe, thecourse of the nerve is followed laterally into the foramen (Fig. 5). If the facets havenot been removed entirely, a generous foraminotomy is performed 1 cm lateral to

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FIGURE 4The “safe zone” is created by removing the entire inferior and superior facets,

exposing the medial border of the exiting nerve root, the lateral border of the traversingroot or thecal sack, and the full height of the disc space above the inferior pedicle, withinthe neural foramen. Identify medial pedicle wall, and gently mobilize the shoulder of thetraversing nerve toward the midline. Minimize dissection over the floor of the canal. UseThrombin soaked Gelfoam and bipolar electrocautery to control epidural vessels. Bipolarcautery is used to control the plexus of small veins that surround the base of the pedicleand fill the space between the disc and the axilla of the nerve root

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the origin of the nerve root. Insure that no bony overhang exists, compromisingexposure of the disc space. If foraminal encroachment is encountered, complete aGill decompression using a burr or rongeurs.

In revision cases, carry the exposure and dissection down as close to the duraas possible, staying in the midline to avoid leaving a large mass of scar attached tothe thecal sack. Identify all bone margins from the previous decompressions orfusions, and develop the plain between the bone and adjacent scar or tissue.Magnification is helpful. After the soft tissue exposure is completed, it isimperative to first find the medial wall of the pedicle below the expected PLIFlevel. This allows the surgeon to precisely locate the traversing nerve root, the discspace above the superior wall, and the foraminal canal. Once these structures areidentified, the dissection becomes less arduous. In these cases, the exiting nerveroot is often hard to visualize, but it can be found hugging the base of the pedicleabove before traversing in a collection of scar and fibrovascular tissue across thesuperior margin of the disc to the exit.

SEGMENTAL INSTRUMENTATIONOnce laminectomy and foraminotomies are completed, pedicle screw placement isrelatively easy (Fig. 6). Because the disc space will be held open by distraction

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FIGURE 5Extensive release of the contracted annular fibers facilitates disc-spacedistraction

and reduction of sagittal imbalance or spondylolisthesis. Once the facetectomy has beencompleted, a nerve hook or penfield elevator retracts and protects the nerve root laterally asthe annulotomy is extended as far into the foramenas possible. The nerve root retractor thenprotects the dura as the medial annulus is released. A complete discectomy follows.


forces placed through these screws, placement should be optimal. The properpedicle entry point for each screw is confirmed by palpating the superior andmedial walls of the pedicle from within the canal. Once the pedicle screws areinserted, contoured “working” rods are placed in preparation for disc-spacereconstruction.

THE PLIF PROCEDUREDisc-space distraction: After pedicle screw placement, a generous discectomy isperformed on both sides of the thecal sac (Fig. 6). A thick epidural scar, a partiallycalcified annulus, and osteophytes can make the distraction maneuver difficult.Attempting to overcome these tethers by force can result in pedicle screwloosening, endplate fracture, or vertebral fracture.

Beginning in the “safe zone,” dissect laterally around the side of the annulus,and then medially under the dura. Protecting the thecal sac medially, perform theannulotomy, releasing the annulus laterally well into the foramen. Protect theexiting nerve root with a Penfield elevator. Remove disc material with curettes andpituitary rongeurs. A small osteotome may be used to remove any overhangingosteophytes. Attempts to apply distraction through the screws themselves can lead

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FIGURE 6After decompression and facetectomy, superior and inferior pedicles are

visualized. An elevator or nerve probe follows the course of the nerve laterally into theforamen. If foraminal encroachment is encountered, complete a Gill decompression. Oncelaminectomy and foraminotomies are completed, pedicle screw placement is relativelyeasy. The proper pedicle entry point for each screw is confirmed by palpating the superiorand medial walls of the pedicle from within the canal. After pedicle screw placement, agenerous discectomy is performed on both sides of the thecal sac. Thick epidural scars,partially calcified annulus, and osteophytes must be removed.

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to loosening and pedicle fracture. Use a system of sequential paddles to distract thedisc space (Fig. 7). Distraction forces can be applied in a controlled fashion throughthe endplates, correcting sagittal alignment and restoring vertical height. Once thedesired distraction or deformity correction is achieved, temporary tightening of thescrews will hold the construct in place, and maintain distraction.

If three-dimensional deformity correction needs to be performed, such ascorrection of anterolisthesis or rotational scoliosis, disc-space distraction must beperformed first. After this, the vertebral body can be pulled back or manipulatedinto proper alignment while the disc space is held distracted.

When using paddle-style distractors for lateral-listhesis or scoliotic defor-mities, the distractor can significantly ease the translation of the displaced vertebrainto proper sagittal and coronal alignment. If, for example, the vertebra iscollapsed, translated, and angled to the right, placing the paddle distractor into thedisc space in the right “safe zone” and then rotating left or counter-clockwise will

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FIGURE 7Distraction and endplate preparation in TLIF: (A,B) Nerve root retractors may be

used to retract the nerve root laterally or the thecal sac medially. (C,D) Paddle-typeshavers are inserted parallel to the endplates and then turned in clockwise and counter-clockwise motion. Repetition of this maneuver with paddle shavers of increasing sizes willfacilitate distraction of the disc space and allow for insertion of a larger TLIF cage. Careshould be taken not to place the paddle shavers as far anteriorly as possible to facilitatedistraction of the anterior rim of the endplate, where stronger bone is usually found. Thishelps prevent creating a round channel in between the endplates rather than truedistraction. Source: Images courtesy of Abbott Spine. Abbreviation: TLIF, transforaminallumbar interbody fusion.


elevate and shift the vertebra back to the left or neutral position. This maneuvercan be used at multiple levels in the case of degenerative scoliosis to morecompletely correct the deformity, holding the correction in place with the workingsystem until the reconstruction is completed with multilevel PLIFs.

Initial distraction begins with placement of the smallest paddle into one sideof the disc space. Care is taken to protect the nerve roots at all times. A small malletis used to tap the spreader to a depth of 30mm, disrupting some of the annularfibers that will restrict height restoration. The spreader is rotated 90˚ to open thedisc space. A second spreader is inserted on the opposite side and rotated to 90˚.The first spreader is removed, and the next larger spreader (10mm) is inserted. Thesequential technique is continued back and forth until maximal distraction isachieved. Once maximal distraction has occurred, the pedicle screw fixation nutsare tightened on the working rods or plates to maintain distraction.

Disc-space preparation: Disc-space preparation can be achieved in one of threeways. The disc can be removed manually using osteotomes, curettes, and variousbiting rongeurs. Sequentially sized paddle shavers are available that can assist inendplate preparation (Fig. 7). Finally, broach, reaming, or rotating drum systemshave emerged in the attempt to “automate” the disc-space preparation process.

The goal is to remove all of the endplate cartilage, and expose a large surfaceof bleeding bone for fusion, without fracturing the endplate. Paddle shavers arepopular with many surgeons because they clean the endplate over a curved radius,and because they create a precise interspace gap for cage or ramp insertion.Broaches and reamers must be used carefully to avoid violating the endplate boneand reducing the subsequent loading strength of the anterior column.

Once the discectomy is completed, the anterior annulus is gently probed witha blunt-tipped instrument to confirm its integrity. The prepared interspace is readyto be filled with two final elements—some form of graft material and an interbodyspacer.

THE TLIF PROCEDUREThe difference between a far lateral PLIF approach and a true TLIF is subtle, andsometimes little more than a matter of semantics. The key point is that the TLIFbegins with a resection of the facet joint and exposure of the foramen, intending tominimize contact with the dural sack from the start.

The open TLIF approach begins with a wide laminectomy, as above, butretains the facet joint on one side (the asymptomatic side, usually), while a widefacetectomy or complete facet excision is carried out on the other. Working frommedial to lateral, the nerve root can be traced across the surface of the disc and iswell visualized in the zone where the annulotomy will be performed. Bipolarcautery around the base of the pedicle, and along the leash of tissue accompanyingthe nerve root through the foramen, will maintain hemostasis.

The advantage of the TLIF approach over the classic PLIF is that the lateralentry into the disc allows near-complete evacuation of the intervertebral spacethrough a unilateral annulotomy. Protecting the root with a Penfield and the durawith a nerve root retractor, the annulus within the foramen is widely incised andremoved with pituitary rongeurs. After evacuating the easily removed annulusand any remnants of the nucleus, a series of curved and offset curettes can be usedto scrape the endplates and release the cartilage endplate from the underlyingbone. Paddle shavers can be used around the entry to the interspace, but it is hard

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to angle these to reach much beyond the midline. Curved grabbers are used tocross underneath the midline to remove disc material all the way to the farannulus. Carefully measure the length of instrument being inserted, and carefullyobserve the angle and orientation of each instrument to insure that the far annulusis reached, but not breached. Tactile feedback is important—the curette raspingagainst the bony endplate is certainly within the disc space.

After preparing the disc interspace, the trial implant is checked for fit. At thispoint, any overhanging remnants of the facets above or below may impede directplacement. These impediments should be removed to make sure the final implantcan be inserted at the proper angle without abutting or abrading the nerve root orrisking an off-angle placement and malpositioning.

Once the final cage is selected, an appropriate graft material is prepared forinsertion into the space, prior to placement of the cage or spacer. While the PLIFtechnique typically involves placement of paired parallel cages or ramps, the TLIFallows the surgeon to stabilize the anterior column with a single cage placedtransversely across the disc space.

n MIS SURGICAL TECHNIQUES: TLIF

EXPOSURE, DECOMPRESSION, AND MOBILIZATIONBoth a c-arm and an operating microscope should be draped in sterilely andbrought into the field prior to making an incision. Typically, the base of the c-arm isplaced opposite from the surgeon and the base of the operating microscope on thesame side with the surgeon. This may minimize crowding of the equipment in thefield.

The motion segment requiring reconstruction is identified under fluoroscopywith the use of guide wires. Bilateral Wiltse-type muscle-splitting approaches areused to place the pedicle screws and to perform the TLIF. Alternatively,percutaneous incisions may be used for screw placement opposite the TLIFprocedure. For a single-level reconstruction with four pedicle screws, the authorprefers to perform two one-inch paramedian incisions. The two-incision techniqueis also suitable for multilevel reconstructions. The incisions may be extended asneeded. Typically, an incision no longer than 1.5 inch may suffice for a two-levelreconstruction. In general, the author performs the TLIF through the side on whichthe patient’s radicular symptoms are more severe. Bilateral decompression shouldonly be considered if severe bilateral radicular symptoms are present or if thepatient’s preoperative imaging studies reveal central or contralateral lateral recessstenosis.

There is some debate as to the right choice of access portal. In general, abigger access portal does not necessarily translate into better visualization and easeof surgery. In fact, access tubes larger than 22mm may increase tissue creep fromsurrounding muscles that often will contract with the use of electrocautery, sincemost patients will not be paralyzed to allow adequate electromonitoring. Theproblem of topography mismatch at the end of the access portal with the spine maybecome more relevant with highly arthritic, deformed facet joints, or degenerativescoliosis. Conceivably, access portals could be made much smaller than 22mm andone could move from a quasi-mini-open to a true percutaneous procedure oncemore specialized instruments become available.

An access portal such as the Metrix� tube system (Medtronic SofamorDanek Q4) can be placed on the side of decompression, verifying positioning at the

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operative level with intraoperative fluoroscopy. Typically, a 22-mm tube will offergood visualization, and allow for passage of instruments while minimizing tissuecreep and loss of visualization during manipulation of the surgical field.Monopolar or bipolar electrocautery can be used to sparingly denude the facetjoint capsule medially to the junction with the lamina of the superior level andlaterally just far enough to dissect any muscular attachments.

SEGMENTAL INSTRUMENTATIONPedicle screws can be placed either before or after the TLIF, depending on whethera self-distracting interbody fusion device is being used. However, once the pediclescrews are inserted, “working” rods can be placed in preparation for disc-spacereconstruction.

THE MINIMALLY INVASIVE TLIF PROCEDUREThe inferior aspect of the superior articulating facet is amputated at the junctionwith the lamina and at the level of the pedicle of the superior vertebral body. Thesuperior aspect of the inferior articulating facet is resected just to the pedicle of theinferior vertebral body. When done through an MIS access portal, these maneuverscan be performed with bayoneted osteotomes, pituitary rongeurs, and a drill bit(Midas Rex). Bone from the facet joint resection is morselized and saved for lateruse during the interbody fusion. Bleeding from the lateral facetal venous system iscontrolled with bipolar electrocautery. The decompression is then extendedmedially superiorly and inferiorly with bayoneted Kerrison rongeurs to allowadequate central and lateral recess decompression of the traversing nerve root. Theexiting nerve root is mobilized as needed with great care to avoid injury to thedorsal root ganglion (DRG). The combination of these maneuvers usually exposesthe intervertebral disc for the subsequent microdiscectomy and cage placement.Any epidural bleeding may be controlled with thrombin-soaked injectableGelfoam.

An annulotomy is performed through the tube with a long-handledannulotomy knife, and the annulotomy is then enlarged sequentially withinterbody paddle shavers (Fig. 7). The goals of the endplate preparation aresimilar to those of the PLIF procedure. Bayoneted straight and angled pituitaryrongeurs, angulated spoon-shaped, and down-pushing curettes are used for theremoval of the disc material and the endplate decortication. Local bone graft withor without an absorbable collagen sponge reconstituted with recombinant bonemorphogenetic protein 2 (Infuse� Q5) is placed into the intervertebral disc space via afunnel/tamp device prior to insertion of the cage.

Resection of posterior lip osteophytes may be necessary to introduce thecage. However, leaving these lip osteophytes may reduce the small risk of posteriorcage dislocation. Insertion of the cage may be facilitated by distraction of theopposite pedicle screw–rod construct. In addition, anterior release and distractioncan be facilitated by placing and rotating dilators and shavers most anteriorly. Theuse of nerve root retractors is recommended only for medial retraction of the thecalsac. Lateral retraction of the exiting nerve root should be avoided to minimize therisk of damaging the DRG while compressing the exiting nerve root against thepedicle. Typically, a single intervertebral spacer is placed and directed just acrossthe midline using biplanar fluoroscopy ( Figs. 8 and 9).

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When done through an access portal, a microscope may offer betterillumination and visualization of the surgical anatomy. Some typical microscopicviews of the various stages of the TLIF procedure are shown in Figures 10 and 11. Q6

n STRATEGIES FOR INSERTION OF GRAFT AND IMPLANT

Historically, autograft has been the material of choice for interbody fusion, usuallytaken from the lamina and spinous process. Allograft, augmented with localautograft or aspirated marrow, is also frequently used to augment the autograftwhen the quantity obtained is limited.

Although biological additives can speed up or improve fusion rates, sometype of interbody spacer is needed to maintain interspace height while the fusiontakes place. There are several options to maintain interbody height: threaded cages,carbon-fiber and PEEK cages, and allograft ramps are all viable options for PLIF orTLIF instrumentation. While the goals and fundamental principles remain constant

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FIGURE 8Preparation of interspace and insertion of TLIF cage: (A,B) The discectomy and

endplate preparation may be facilitated by the use of an articulating rasp that can beadvanced to the opposite side of the interspace. This allows for additional endplatedecortication and formation of a track for subsequent cage insertion. (C,D) Prior toinsertion of the TLIF cage, all free disc material should be removed and bone graft shouldbe packed into the interspace. The cage may be introduced with an articulating insertiondevice. This allows for position of the TLIF cage in an anterior and central position, where itwill allow for best restoration of lumbar lordosis and is biomechanically in the mostadvantageous position. Source: Images courtesy of Abbott Spine. Abbreviation: TLIF,transforaminal lumbar interbody fusion.


with the different types of spacer, the techniques for application and the nuances oftheir use do vary considerably.

THREADED CAGESThreaded interbody cages have been developed for anterior interbody fusion, andare used as stand-alone devices in the presence of intact posterior elements. Whenthreaded cages have been used as PLIF spacers, without segmental fixation, it hasresulted in a significant incidence of mechanical failure Q2(23–25). Placement ofpaired threaded cages as interbody spacers requires a wide laminectomy, withbilateral facetectomies, in order to create a wide enough “safe zone” to get theworking cannula and reamers safely past the thecal sac and nerve roots. If thesurgeon attempts to spare the facet joints to maintain posterior stability, the onlycage that can be safely placed may be too small, limiting endplate contact anddistraction. The smaller cage cannot provide sufficient anterior stability, predis-posing to mechanical failure. On the other hand, if the surgeon removes enoughbone to place an optimal cage, the facet joints and posterior soft tissues may be

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FIGURE 9Interbody grafting technique for TLIF: proper technique greatly improves

success. The anterior disc space is packed first (A), followed by the lateral recess on theside for first cage placement (B), before the cage is placed (C), the void across the midlineis filled by packing this bone gently up against the opposite side (D) followed bycompressing the construct. Abbreviation: TLIF, transforaminal lumbar interbody fusion.

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unable to stabilize the spine in flexion, extension, or torsion. This also predisposesto mechanical failure, postoperative instability, and derangement. Revision of thesecases is difficult.

To place threaded cages optimally, a wide laminectomy during PLIF isnecessary. Once the lateral third of the disc space is clearly visualized, the thecalsac is retracted medially with a large nerve root retractor. An annulotomy iscreated just medial to the pedicle, and the bullet distractor is impacted into place.The contralateral distractor is placed in the same manner, and the bullets are thenexchanged for sequentially larger distractors until the disc space is restored tonormal height and the distraction bullets are firmly seated and difficult to remove.The working cannula is then advanced over the obturator used for distractorplacement, and impacted into place. The cannula, once seated, maintains disc-space height after the distraction bullet is removed. The cage placement site is thensequentially reamed, usually to a size 3.0mm smaller than the selected cage. Q2Theendplates are then tapped for cage placement, and a threaded cage, packed withautograft bone harvested during the laminectomy, or harvested from the iliac crestthrough a separate, small incision, is inserted. The contralateral cage is then placedin the same fashion. Unless sufficient bone has been left within each facet to

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FIGURE 10Still photograph through the operating microscope and a 22-mm Metrix� tube

illustrating the initial steps of the minimally invasive TLIF technique: (A) the facet joint mustbe identified as shown here with a Penfield instrument; (B) a drill-bit may be used toremove the facet joint; (C) a bayoneted Woodson dural elevator may be used to feel for thesuperior and inferior pedicles, any remaining facet joint, and lamina. In addition, themedial—lateral dimension of the facetectomy side may be determined; (D) an angulatedforaminotomy Kerrison rongeur may be used to reach across the midline, inferiorly, andsuperiorly, thereby enlarging the extent of the decompression beyond the field of theaccess portal; (E,F) paddle chanvers are inserted into the disc space Q7and should berotated to facilitate the discectomy and endplate preparation. Abbreviation: TLIF,transforaminal lumbar interbody fusion.


provide a posterior stabilizer, the author recommends instrumenting the posteriorelements after cage placement.

In any case, threaded cages are not suitable for an MIS TLIF procedure, as theproper exposure cannot be obtained using an MIS technique, nor can the cageorientation be accomplished through a unilateral approach.

CARBON-FIBER AND PEEK CAGESCarbon-fiber cages are not intended as stand-alone devices. Carbon-fiber cagesmust be used in conjunction with pedicle screw fixation. When used incombination with appropriate posterior instrumentation, however, they provideexcellent initial stability, allow correction of axial and sagittal deformities, andfacilitate a high rate of successful fusion. These radiolucent devices permit anaccurate assessment of the progress of graft incorporation and interbody fusion.

Carbon-fiber cages were developed in the late 1980s and have been usedextensively, worldwide, with very few device-related complications. They haverecently become available in a tapered form for use when the need to restore andmaintain segmental lordosis is great. They maintain their position and alignmentthrough an interference fit between the two endplates, so it is important to selectthe largest cage that will fit the interspace without compromising the endplates.Brantigan cages are the most commonly used devices now available. When packedwith bone graft, they combine mechanical stability with osteoconductive andosteoinductive properties (10,11). The carbon-fiber composite material withstands

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FIGURE 11Still photograph through the operating microscope and a 22-mm Metrix tube

illustrating final steps of the minimally invasive TLIF technique: (A) after the discectomyand endplate preparation and prior to the cage insertion; (B) a trail may be used; (C) theinterspace should be filled with bone graft and a funnel device is uniquely suited for thisportion of the fusion procedure; (D,E) then the cage is inserted and tapped across themidline in an oblique anterior position; (F) hemostasis may be achieved with thrombin-soaked Gelfoam. Abbreviation: TLIF, transforaminal lumbar interbody fusion.

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compressive loads and resists migration. The contained graft stimulates fusion.Successful placement of the cage requires meticulous preparation of the interspaceand vertebral endplates, however (26,27).

PEEK is a hard, radiolucent plastic that was introduced as a material forinterbody fusion cages in 1997. It can be used in conjunction with carbon-fiberreinforcement or as pure PEEK. Most of these devices use radio marker dots,allowing the surgeon to follow the implant during insertion in between the vertebralbody endplates. Desogus et al. recently evaluated the performance of PEEKposterior interbody fusion cages in a prospective analysis (28). Twenty patients hadposterior interbody lumbar fusion with PEEK cages. Their clinical and radiologicaloutcomeswere evaluatedwith controls at 1, 3, 6, and 9months postoperatively. Theydetermined that clinical results were considered satisfactory in 75% of the cases.There were no intra- or perioperative complications. There was no displacement ofthe cages. No signs of unsuccessful fusionwere observed. Desogus et al. determinedthat interbody PEEK cages “fulfill the objective of stabilizing the treated segmentimmediately and subsequently” (28). They even suggested that they can be used asstand-alone devices, provided proper surgical technique and sound clinicalindications are used. Cutler et al. recently determined that both PEEK cages andfemoral cortical allografts were equally effective in promoting interbody fusion,while “maintaining postoperative disc-space height, and achieving desirableclinical outcomes in patients who undergo TLIF with pedicle screw fixation” (29).In addition, they found that PEEK cages had a lower incidence of subsidence andpermitted easier visualization of bone growth through the cage.

After creating the annulotomy, the paddle distractors are introduced into thedisc space, and the disc space is sequentially distracted to its optimal height. Withthe largest distractors in place, the pedicle screws are tightened to the workingplate to hold distraction and alignment. The paddle shavers are then introduced,sequentially, in ascending diameters, and the cartilage and soft tissue are scrapedclean from the endplate bone. Care is taken to clear both the lateral recesses of thedisc and the midline area between the annulotomy portals. Reverse-facing curettesand scrapers are used to complete the debridement.

Before placing the cages, a portion of the morselized autograft harvestedduringdecompression is packed into the anterior disc space and impacted to denselyfill that portion of the disc space (Fig. 9). Bone is packed into the lateral disc space onthe side to be instrumented first, and the trial implant is positioned and impacted intoplace. The trial should fit firmly, square to the endplates, and should be countersunk2.0 to 4.0mm (Fig. 11b). The trial is removed and the cage, packed with autograftmorsels, is introduced through the annulotomy and impacted into place. Once thiscage is seated, the midportion of the disc space is packed with autograft from thecontralateral portal. After packing the lateral recess as well, the second cage isintroduced and impacted into place. The pedicle fixation is then released, and theconstruct compressed vertically to capture the cages and restore lordosis.

Once impacted, a lateral radiograph is taken to confirm cage placement andsagittal alignment. The composite material is radiolucent, allowing radiographicevaluation of the graft mass, and radio-opaque beads allow visualization of thecage margins to confirm position.

A variety of PEEK cages are now available for unilateral placement, andspecifically for MIS TLIF placement. These cages are intended for transverseplacement, and provide both parallel and lordotic contours to maintain disc-spaceheight and restore sagittal alignment.

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ALLOGRAFT RAMPSAllograft ramps are used in the same fashion as the Brantigan cages. They are notintended as stand-alone devices, and must be used in conjunction with a posteriorfixation system. Applied in this fashion, they provide immediate axial andsagittal/rotational stability and a high rate of fusion.

A number of sources of allograft ramps exist, each with slightly differentcontours and insertion systems. These nuances are relatively unimportant so longas the surgeon prepares the interspace meticulously and places the graft properly.Contemporary products are not ethylene oxide sterilized, and previous concernsover nonunion rates have been tempered considerably.

The interspace is prepared as for the Brantigan cage placement. Afterdistracting the disc space and provisionally fixing the pedicle screw system tomaintain distraction, the endplates are completely cleared of soft tissue andcartilage using the paddle shavers and curettes. Once the disc space has beencompletely evacuated and the endplates scraped to bare, bleeding bone, up to 10 ccof morselized bone graft is packed anteriorly into the disc interspace. Using boneimpactors, the bone is packed tightly along the anterior annulus and into the lateralrecesses. The trial for the allograft ramp is then inserted one side at a time todetermine the proper graft size and to insure that the graft will be properlycountersunk when finally placed. The trial is then withdrawn and the selectedramp placed on the first side and impacted into place. When properly sized, theramp should fit firmly but not require excessive effort to impact. If the ramp is tooloose, it may migrate or tilt when additional graft is placed.

Once the first ramp is in place, the remaining morselized graft is impactedinto the midline interspace to fill the gap between the ramps. The second ramp isthen placed and the distraction instrumentation is released. The pedicle screws arethen compressed along the rod to restore lordosis and lock the ramps in place.A final radiograph is taken to document position and sagittal alignment.

n POSTEROLATERAL FUSION AND CLOSURE

After open PLIF or TLIF through a midline approach, the wound is copiouslyirrigated and the remaining bone surfaces decorticated. An autograft can be takenfrom the posterior iliac wing, and is particularly useful in patients undergoingrevision surgery and those predisposed to fusion failure (smoking history, etc.).The working rods or plates are removed and the final implants are placed andtightened in compression to restore lordosis and improve the chance of bony fusion(Wolff’s Law). Depending on surgeon preference, the PLIF can be performed withor without a posterolateral fusion. The bone graft is layered over any decorticatedsurfaces and the final implant tightening is completed. Before closure, it isimportant to check all exposed nerve roots to make sure no loose autograft hasfallen into the foramen. The wound is closed in a layered, watertight fashion. Adrain is optional.

After TLIF, it is up to the surgeon to decide whether or not to include aposterior lateral fusion. However, posterolateral fusion may be more difficult whenutilizing a minimally invasive access portal such as Metrex or another tube system,due to the inability to adequately decorticate the posterior elements. It is possibleto directly visualize the posterolateral gutter including the two adjacent transverseprocesses through the minimal incision with the use of either a small self-retaining

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retractor or hand-held retractors. Through this small aperture, the surface of thelateral facet and the transverse process are directly available for decortication andgraft placement.

n CAVEATS

If bleeding is profuse during endplate preparation, distraction can be temporarilyreleased and the space packed with Gelfoam gauze. Bleeding from exposed bonewill usually abate with a little time. Care must be taken not to penetrate theanterior annulus due to the risk of injuring the great vessels. Careful attentionshould be paid to the depth of disc-space preparation. No instrument should beinserted more than 30mm into the disc space.

In the treatment of degenerative scoliosis, the focus needs to be on distractionand correction of the concave side of the deformity. Once corrected, it may only benecessary to use a unilateral cage or ramp to prevent collapse on the concave side.The convex side of the disc space may be packed with morselized bone. Oncemastered, this technique can be performed unilaterally using a minimally invasiveapproach Q2. This construct is more cost effective, with the same surgical and clinicaloutcomes.

The choice and placement of the interbody fusion cage will undoubtedlyhave an effect on postoperative outcomes. There are various banana or bullet-shaped TLIF cages on the market that are made from either titanium, PEEK, orcarbon fiber. Every attempt at maximizing distraction should be made to facilitateinsertion of the tallest possible cage. Compression injury to the exiting nerve root isof concern. However, this can be minimized by maximizing distraction with theinterbody shavers and the pedicle screw instrumentation of the opposite side, asthe nerve root will retract proximally away from the disc space. Depending on thecage design, the use of trailing tools may facilitate its insertion.

There are other problems inherent to the cage design. For example, a bullet-shaped cage may be easier to insert, particularly, if large posterior endplateosteophytes are present. However, distraction across the interspace may be lostonce the cage is inserted, thus reducing neuroforaminal height. Moreover, it couldincrease the propensity to cage migration, which most frequently will occurposteriorly through the same path of insertion. Therefore, removal of posteriorendplate osteophytes should be carefully considered depending on the particularcage design, as these lip osteophytes may be the only barrier preventing the cagefrom dislodging into the neuroforamen. Compression should be applied across theinterbody fusion segment to prevent this problem. The actual position of aunilaterally inserted cage with respect to anterior–posterior, or medial–laterallocation in the interspace appears to be less significant since there was no evidenceof delayed fusion in the patients studied.

n OUTCOMES

PLIF restores disc-space height to predegenerative levels, placing tension on theanterior longitudinal ligament and the undissected portion of the annulus tomaximize stiffness in extension and lateral bending. Restored sagittal alignmentnormalizes load transmission over the anterior and posterior spinal elements, andminimizes abnormal strains transmitted to adjacent motion segments.

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Disc-space distraction indirectly decompresses the neural elements byrestoring foraminal volume. Using a PLIF procedure without disc-space distractionwas associated with failure of improving leg pain in 55% of subjects (30).

Yashiro et al. (31) compared instrumented intertransverse fusion with andwithout PLIF and found better maintenance of correction and less instrumentationfailure in the PLIF group. The rate of fusion with PLIF was 100%, compared to 56%with intertransverse fusion alone. Brantigan et al. reported a 99% fusion rateamong 178 patients treated with PLIF using carbon-fiber cages, with a clinicalsuccess rate of 86% (32). To date, there is no prospective randomized clinical trialcomparing fusion rates and clinical outcomes after TLIF with or withoutposterolateral fusion. However, 2-year follow-up data are available on patientswho had minimally invasive TLIF. Results suggest clinical outcomes are similar tothose with PLIF procedures (20–22,33,34).

Studies indicate that the addition of posterior instrumentation to the spine ismore important in determining the overall construct stiffness than is the choice ofthe PLIF implant itself. The mechanical benefits of pedicle screw fixation offset therisks associated with their use. Postoperative pain, residual motion, and nonunionare greater for PLIF procedures performed without posterior instrumentation. PLIFand TLIF supplemented with pedicle screw instrumentation have a very lowincidence of hardware complications and loosening, comparable to that for pediclescrew placement alone.

n REFERENCES

1. Hibbs RA. An operation for progressive spinal deformities. NY Med J 1911; 93:1013.2. Albee FH. Transplantation of a portion of the tibia into the spine for Pott’s Disease: a

preliminary report. JAMA 1911; 57:885.3. Watkins MB. Posterolateral fusion of the lumbar and lumbosacral spine. J Bone Joint

Surg 1953; 35A:1014–1018.4. Bridwell KH, Sedgewick TA, O’Brien MF, et al. The role of fusion and instrumentation

in the treatment of degenerative spondylolisthesis with spinal stenosis. J Spinal Disord1993; 6:461–472.

5. Yuan HA, Garfin SR, Dickman CA, et al. A historical cohort study of pedicle screwfixation in thoracic, lumbar, and sacral spinal fusions. Spine 1994; 19(Suppl):2279S–2296S.

6. Mercer W. Spondylolisthesis with a description of a new method of operative treatmentand notes of ten cases. Edinburgh Med J 1936; 43:545–572.

7. Jaslow IA. Intercorporal bone graft in spinal fusion after disc removal. Surg GynecolObstet 1946; 82:215–218.

8. Cloward RB. The treatment of ruptured lumbar intervertebral discs by vertebral bodyfusion. J Neurosurg 1953; 10:154–168.

9. Lin PM, Caulitti M, Joyce MF. Posterior lumbar interbody fusion. Clin Orthop 1983; 180:154.

10. Brantigan JW, Steffee AD. A carbon fiber implant to aid interbody lumbar fusion. Twoyear clinical results in the first 26 patients. Spine 1993; 18:2106–2107.

11. Brantigan JW. Pseudarthrosis rate after allograft posterior lumbar interbody fusion withpedicle screw and plate fixation. Spine 1994; 19:1271–1280.

12. Harms J, Beele BA, Bohm H, Jeszenszky D, Stoltze D. Lumbosacral fusion with harmsinstrumentation. In: Margulies JY, al. eds. Lumbosacral and Spinopelvic Fixation.Philadelphia: Lippincott-Raven, 1996.

13. Harms J, Jeszenszky D, Stoltze D, Bohm H. True spondylolisthesis reduction andmonosegmental fusion in spondylolisthesis. In: Bridwell KH, DeWald RL, eds. The

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158 n McLain

Textbook of Spinal Surgery, 2nd edn. Philadelphia: Lippincott-Raven, 1997,pp. 1337–1347.

14. Jenis LG, An HS. Posterior lumbar interbody fusion for spondylolisthesis. Semin SpineSurg 1999; 11:56–66.

15. Brislin B, Vaccaro AR. Advances in posterior lumbar interbody fusion. Orthop ClinNorth Am 2002; 33:367–374.

16. Hee HT, Castro FP Jr, Majd ME, Holt RT, Myers L. Anterior/posterior lumbar fusionversus transforaminal lumbar interbody fusion: analysis of complications andpredictive factors. J Spinal Disord 2001; 14:533–540.

17. Humphreys SC, Hodges SD, Patwardhan AG, Eck JC, Murphy RB, Covington LA.Comparison of posterior and transforaminal approaches to lumbar interbody fusion.Spine 2001; 26:567–571.

18. Rosenberg WS, Mummaneni PV. Transforaminal lumbar interbody fusion: technique,complications, and early results. Neurosurgery 2001; 48:569–574; discussion 74–75.

19. Whitecloud TS 3rd, Roesch WW, Ricciardi JE. Transforaminal interbody fusion versusanterior-posterior interbody fusion of the lumbar spine: a financial analysis. J SpinalDisord 2001; 14:100–103.

20. Holly LT, Schwender JD, Rouben DP, Foley KT. Minimally invasive transforaminallumbar interbody fusion: indications, technique, and complications. Neurosurg Focus2006; 20(3).

21. Schwender JD, Holly LT, Rouben DP, Foley KT. Minimally invasive transforaminallumbar interbody fusion (TLIF): technical feasibility and initial results. J Spinal DisordTech 2005; 18(Suppl):S1–S6.

22. Foley KT, Holly LT, Schwender JD. Minimally invasive lumbar fusion. Spine 2003;28(15 Suppl):S26–S35.

23. Brodke DS, Dick JC, Kunz DN. Posterior lumbar interbody fusion: a biomechanicalcomparison, including a new threaded cage. Spine 1997; 22:26–31.

24. Elias WJ, Simmons NE, Kaptain GJ. Complications of posterior lumbar interbody fusionwhen using a titanium threaded cage device. J Neurosurg 2000; 93:45–52.

25. Goh JCH, Wong HK, Thambyah A. Influence of PLIF cage size on lumbar spine stability.Spine 2000; 25:35–40.

26. Hoshijima K, Nightingale RW, Yu JR. Strength and stability of posterior lumbarinterbody fusion. Spine 1997; 22:1181–1188.

27. Rapoff AJ, Ghanayam AJ, Zdeblick TA. Biomechanical comparison of posterior lumbarinterbody fusion cages. Spine 1997; 22:2375–2379.

28. Desogus N, Ennas F, Leuze R, Maleci A. Posterior lumbar interbody fusion with peekcages: personal experience with 20 patients. J Neurosurg Sci 2005; 49(4):137–141.

29. Cutler AR, Siddiqui S, Mohan AL, Hillard VH, Cerabona F, Das K. Comparison ofpolyetheretherketone cages with femoral cortical bone allograft as a single-pieceinterbody spacer in transforaminal lumbar interbody fusion. J Neurosurg Spine 2006;5(6):534–539.

30. Verlooy J, De Smedt K, Selosse P. Failure of a modified posterior lumbar interbodyfusion technique to produce adequate pain relief in isthmic spondylolytic grade Ispondylolisthesis patients: a prospective study of 20 patients. Spine 1993; 18:1491–1495.

31. Yashiro K, Homma T, Hokari Y, Katsumi Y, Hirano A. The Steffee variable screwplacement system using different methods of bone grafting. Spine 1991; 16:1329.

32. Brantigan JW, Steffee AD, Lewis ML. Lumbar interbody fusion using the Brantigan I/Fcage for posterior lumbar interbody fusion and the variable pedicle screw placementsystem. Spine 2000; 25:1437–1446.

33. Moskowitz A. Transforaminal lumbar interbody fusion. Orthop Clin North Am 2002;33:359–366.


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Extreme Lateral Interbody Fusion

11 Eli M. Baron and Neel Anand

n INTRODUCTION

Extreme lateral interbody fusion (XLIF) is a novel, minimally invasive techniquefor performing interbody fusion (1). The advantages of interbody fusion overposterolateral fusion include higher fusion rates, achievement of better sagittallordosis, and better outcomes (2–5). When compared with posterior methods ofinterbody fusion, anterior lumbar interbody fusion (ALIF) provides the theoreticaladvantages of more extensive discectomy, avoidance of scaring adjacent to theneural elements, and sparing of the posterior elements (6–8). Nevertheless, ALIF isassociated with complications including visceral and ureteral injury (9,10),vascular injury (11,12), and sexual dysfunction (10), among others. Althoughminimally invasive techniques such as the mini-open (13,14) and laparoscopic andendoscopic techniques (15–17) have been described, these require a steep learningcurve and the potential for the above complications remains (1). An endoscopicminimally invasive lateral transpsoas approach has also been described (18).Nevertheless, given the complexity of this technique and increased operation room(OR) set-up time over the XLIF, this represents a historical technique predating theXLIF.

XLIF uses a minimally invasive, transpsoas approach to the retroperitonealspace. Two incisions are used, where the surgeon through a posterior paraspinalincision uses his/her finger to enter the retroperitoneal space and subsequentlyescort a guide wire into position directly over the disc. This technique protects theviscus and prevents possible injury. Additionally the use of an electromyographic(EMG) monitoring system Q1(Neuro-Vision JJB EMG monitoring system), asdeveloped by NuVasive (NuVasive Inc., San Diego, CA), ensures safe access tothe disc through the psoas muscle, its own. All dilators used are insulated at thetips, thus allowing EMG monitoring as the dilators are introduced via thetranspsoas approach to the disc. As the dilators are introduced, muscles innervatedby the lumbar plexus are monitored. Should a dilator pass close to the plexus, theoperator is warned both visibly on a graphic display and audibly. The surgeon canadjust the trajectory of the dilator and move it away from the lumbar plexus andconfirm it again with the monitoring as the warning signals disappear. An addedbenefit of XLIF is the fact that while ileus has been described as occurring in asubstantial number of patients undergoing ALIF (10), it is unusual post-XLIF. Incomparison with other lateral transpsoas approaches to the spine such as the mini-open approach and the laparoscopic/endoscopic approaches, the learning curve issignificantly reduced. Further, the procedure does not require the assistance of an

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Eli M. Baron and Neel Anand Institute for Spinal Disorders, Cedars—Sinai Medical Center, LosAngeles, California, U.S.A.

161

access surgeon. Other advantages of the procedure include the fact that the anteriorlongitudinal and posterior longitudinal ligaments remain intact, the lack of bonyresection, reduced operative time when compared to other anterior/lateralapproaches, reduced postoperative analgesic requirements, and reduced post-operative hospital stays.

n INDICATIONS

XLIF is indicated as an alternative to ALIF from L1-L2 down to L4-L5, when directcanal decompression is not indicated through the same approach. It is particularlyuseful for lumbar degenerative scoliosis (Fig. 1), where the patient is positionedwith the apex facing upward. It is also a useful alternative to ALIF, especially whena patient has had prior abdominal surgery, provided no retroperitoneal surgery hasbeen done on the side of approach. The approach may be useful in the future fornucleoplasty and total disc replacement, in addition to revision of a failedarthroplasty prosthesis (19). The rib cage limits the technique at rostral levels whilethe iliac crest limits the technique caudally. Contraindications for XLIF include theL5-S1 level, lumbar deformities with greater than 30˚ of rotation, degenerativespondylolisthesis greater than or equal to grade 3, bilateral retroperitonealscarring, and medical comorbidities that would be a contraindication to fusion.

n POSITIONING

After intubation and placement of EMG-monitoring leads, the patient is positionedin the lateral decubitus position (Fig. 2). For cases not addressing lumbar scoliosis,the patient is positioned in the right lateral decubitus position, i.e., left flank up. Incases with scoliosis, the patient is positioned in lateral decubitus with the convexside up. We prefer to use bolsters to position the patient. We use a radiolucent tablewith a slider where the patient’s flank is placed over the kidney rest. Through acombination of lowering the foot-end of the table, and the head-end of the table,the distance between the iliac crest and rib cage is maximized to facilitate theprocedure. Raising the kidney rest may afford additional access. Finally, the patientis firmly secured to the table with silk tape. It is critical to ensure that the patient isappropriately and securely positioned on the table. A c-arm is then brought in forlateral fluoroscopy.

n PROCEDURE

The skin is then marked using lateral fluoroscopy (Fig. 3). It is important to ensurethat a true lateral image is obtained. A marker is used to identify the center of theappropriate disc space and the skin overlying the space is marked. This should bedone at each level where discectomy is planned. Subsequently, small horizontalincisions are marked. A second incision, for the surgeon’s finger to serve as a guideto the retroperitoneum and spine, is marked posterior to these marks on the skin atthe junction between the erector spinae muscles and the abdominal obliques(Fig. 4). The skin is then prepped and draped in the usual manner.

The posterior incision is made first. The fascia is divided with a monopolar.Blunt dissection with scissors is used to spread muscle fibers and pop through theabdominal fascia into the retroperitoneal space. The surgeon’s finger is then

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162 n Baron and Anand

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FIGURE 1(A,B) Anterior–posterior and lateral lumbar radiograph of a patient with lumbar

degenerative scoliosis. (C,D) Post-XLIF with correction of deformity followed by posteriorspinal fusion from T10 to the ileum. Abbreviation: XLIF, extreme lateral interbody fusion.

Extreme Lateral Interbody Fusion n 163

inserted, the peritoneum swept anteriorly, and the psoas muscle palpatedinferiorly. Additionally, the transverse processes can be palpated through thepsoas muscle. The finger is then taken directly up within the retroperitoneal spacetoward the lateral wall of the abdomen where the skin incision was marked. Theskin is then incised and the fascia opened with a monopolar. A blunt probe whichis also the first dilator is then introduced through the incision and advancedtoward the tip of the surgeon’s finger. The probe is then “escorted” by thesurgeon’s finger as it is advanced toward the psoas muscle. A lateral radiograph

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FIGURE 2Postpositioning. The kidney rest is elevated. Note the tape used to secure both

the upper torso and the thighs to the table.

FIGURE 3The skin overlying the disc space is marked using fluoroscopy. A k-wire is used to

localize the disc space.


confirms the trajectory of the probe toward the disc. A dynamic stimulation clip isthen snapped onto the probe that connects to the neuromonitoring equipment. Theprobe is now passed through the psoas muscle up to the disc space withneuromonitoring (Fig. 5). A lateral fluoroscopic image should now confirm theprobe to be approximately in the middle of the disc space at the appropriate level.

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FIGURE 4A second incision is marked posteriorly on the skin, marking the junction of

erector spinae muscles and the abdominal obliques. The surgeon should be able to easilyreach with his/her finger from the second incision to the first incision.

FIGURE 5The NeuroMonitoring system is used to assess placement of the individual

dilators and reduce the likelihood of neural injury. (Inset) A screen shot from theNeurovision Monitoring system shows the detection system in the “green range,” which isconsistent with safe dilator passage.


A guide wire is then inserted through the cannulation in the probe and insertedinto the disc, whereupon a lateral and anterior–posterior (AP) fluoroscopic imageis taken and the position confirmed (Fig. 6).

At this stage, sequential dilators are used and passed through the psoas withneuromonitoring. The third and final dilator has markings on it so that the lengthof the retractor blades that would be needed to place the MaxAcess Retractor(NuVasive, San Diego, CA) can be read. Each dilator is insulated throughout, withthe exception of the distal tip, which is connected to a dynamic stimulation clip atthe proximal end of the dilator. The dilator is advanced with a lead attached fromthe monitoring system to the clip. Triggered EMG responses with thresholdsgreater than 10 mA are considered safe. Should the system display values less thanthis, the surgeon can change the trajectory through the psoas muscle.

The MaxAcess retractor is now inserted over the final dilator (Fig. 7). Theself-retaining retractor is opened in a craniocaudal direction to the desired width.Similarly, the AP exposure is obtained by adjusting the middle blade. Fluoroscopyshould be used to confirm the exact position of the retractor over the disc. Theretractor position is then fixed via a rigid articulating arm (which is attached to thebed). We recommend that the surgeon holds the retractor in place while anassistant connects the arm. AP and lateral fluoroscopy are then used to confirm thelocation of the dilated retractor blades toward the center of the disc space onthe lateral view and at the lateral border of the disc space on the AP view. A lightsource is then attached to the retractor.

n DISCECTOMY

Prior to performing the discectomy, soft tissue around the disc space is cleared.Using both direct visualization and triggered EMG probe stimulation of soft tissuesover the disc space to confirm the absence of neural tissue, bipolar cautery is usedto cauterize the soft tissue overlying the vertebral bodies and disc space. If the

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FIGURE 6Fluoroscopy is used to confirm dilator location.


retractor is well positioned, there should be very little to no soft tissue over the discspace. A number 15 blade is used to incise the disc, with the discectomy windowcentered over the anterior two-thirds of the disc space. After removing discmaterial with a pituitary rongeur, a large Cobb dissector is used to separate thecartilaginous end plates from its adjacent vertebral body. The Cobb dissector ispassed under AP fluoroscopic control all the way to the opposite side in order torelease the annulus, enabling maximal deformity correction (Fig. 8). The disc spaceis further prepared using a series of curettes and rasps. End plates are meticulouslyprepared with curettes.

n PREPARATION FOR IMPLANT PLACEMENT

Serial trials are then used as sizers prior to placement of the implant (Fig. 9). Trialsare removed from the disc space using a gentle wiggling motion: a snug trial can be

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FIGURE 7The MaxAcess retractor is inserted over the final dilator. Position should be

confirmed on both anterior–posterior (A) and lateral (B) fluoroscopy.


difficult to remove from the disc space. The final size trial should fit snuggly, withappropriate disc space height (Fig. 10). A corresponding-size large polyether-ether-ketone (PEEK) implant (Core Tek (NuVasive, San Diego, CA) (Fig. 11) is used andimpacted in place ideally in the anterior one-third of the vertebral body. We preferto place a bone morphogenic protein–soaked sponge (Infuse, Medtronic, Memphis)in addition to Grafton putty in the spacer prior to implanting it in the disc space.

n CLOSURE

Once the position of the implant is confirmed and is satisfactory, the retractor isremoved and the incisions are then copiously irrigated with saline solution We use0 Vicryl in a buried manner to close the fascia and then 3-0 Vicryl buried subdermalstitches with steristrips for the skin. We then supplement the XLIF with posteriorinstrumentation. The roles of stand-alone XLIF, supplementation with lateralplating, and posterior instrumentation all still need to be evaluated.

n COMPLICATIONS

Despite normal intraoperative monitoring, patients may have weakness in thepostoperative period. This may be attributable to injury of the psoas muscle or toneural injury. Groin pain and weakness of flexion of the hip is probably due topsoas manipulation and/or hematoma and invariably returns to normal withinfour to six weeks. We have had 3 cases out of 22 that we have done of vastusmedialis weakness in the immediate postoperative period. All occurred with XLIF

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FIGURE 8Anterior–posterior fluoroscopic image confirming the Cobb past the contralateral

annulus, confirming bilateral annular release.


at the L4-L5 level, which we believe is resultant neuropraxia of the lumbar plexus.Two patients returned to normal within six weeks, with one patient regaining herstrength within three months. Other conceivable complications that we have notseen include retroperitoneal hematoma and retroperitoneal organ injury. Thesecond incision, where the surgeon’s finger is used to guide the probe down

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FIGURE 9(A, B) Curettes and rasps used to prepare the disc space.


through the retroperitoneal space, should help ensure a clear path with regard toretroperitoneal organs and vasculature.

n OUTCOMES

Although long-term outcomes in terms of efficacy and fusion rates are yet to bereported, data exist as to the safety and feasibility of XLIF. Wright reportedoutcomes in terms of safety and reproducibility for the initial 145 cases of XLIFperformed in the United States (20). Seventy-two percent of these cases were singlelevel, with L4-L5 (37%) being the most common level fused. Mean blood loss wasnoted at 88 cc and operative time was 74 minutes. There were no vascularcomplications and no abdominal complications. Five patients were noted to havetransient hip flexor weakness, and one patient was noted to have a transient foot

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FIGURE 10PEEK implant used with the XLIF system. Abbreviations: PEEK, polyether-

ether-ketone; XLIF, extreme lateral interbody fusion.

FIGURE 11Anterior–posterior and lateral fluoroscopy confirm excellent placement of the

implant.


drop. One patient was noted to have transient dermatomal numbness. Nearly allpatients ambulated on the day of surgery and were discharged the next day.

n CONCLUSIONS

XLIF is a relatively new, minimally invasive spine procedure especially useful forthe treatment of lumbar degenerative disease and deformity. It has a relatively easylearning curve and is associated with reduced morbidity when compared to ALIF.Long-term outcomes remain to be seen.

n REFERENCES

1. Ozgur BM, Aryan HE, Pimenta L, et al. Extreme lateral interbody fusion (XLIF): a novelsurgical technique for anterior lumbar interbody fusion. Spine J 2006; 6:435–443.

2. Anand N, Hamilton JF, Perri B, et al. Cantilever TLIF with structural allograft andRhBMP2 for correction and maintenance of segmental sagittal lordosis: long-termclinical, radiographic, and functional outcome. Spine 2006; 31:E748–E753.

3. Christensen FB, Hansen ES, Eiskjaer SP, et al. Circumferential lumbar spinal fusion withBrantigan cage versus posterolateral fusion with titanium Cotrel-Dubousset instru-mentation: a prospective, randomized clinical study of 146 patients. Spine 2002; 27:2674–2683.

4. DeBerard MS, Colledge AL, Masters KS, et al. Outcomes of posterolateral versus BAKtitanium cage interbody lumbar fusion in injured workers: a retrospective cohort study.J South Orthop Assoc 2002; 11:157–166.

5. Yashiro K, Homma T, Hokari Y, et al. The Steffee variable screw placement system usingdifferent methods of bone grafting. Spine 1991; 16:1329–1334.

6. Q2Enker P, Steffee AD. Interbody fusion and instrumentation. Clin Orthop Rel Res 1994:90–101.

7. Karim A, Mukherjee D, Ankem M, et al. Augmentation of anterior lumbar interbodyfusion with anterior pedicle screw fixation: demonstration of novel constructs andevaluation of biomechanical stability in cadaveric specimens. Neurosurgery 2006; 58:522–527; discussion 7.

8. Kozak JA, Heilman AE, O’Brien JP. Anterior lumbar fusion options. Technique andgraft materials. Clin Orthop Rel Res 1994:45–51.

9. Gumbs AA, Shah RV, Yue JJ, et al. The open anterior paramedian retroperitonealapproach for spine procedures. Arch Surg 2005; 140:339–343.

10. Rajaraman V, Vingan R, Roth P, et al. Visceral and vascular complications resulting fromanterior lumbar interbody fusion. J Neurosurg 1999; 91:60–64.

11. Baker JK, Reardon PR, Reardon MJ, et al. Vascular injury in anterior lumbar surgery.Spine 1993; 18:2227–2230.

12. Brau SA, Delamarter RB, Schiffman ML, et al. Vascular injury during anterior lumbarsurgery. Spine J 2004; 4:409–412.

13. Brau SA. Mini-open approach to the spine for anterior lumbar interbody fusion:description of the procedure, results and complications. Spine J 2002; 2:216–223.

14. Kaiser MG, Haid RW Jr, Subach BR, et al. Comparison of the mini-open versuslaparoscopic approach for anterior lumbar interbody fusion: a retrospective review.Neurosurgery 2002; 51:97–103; discussion 5.

15. Heniford BT, Matthews BD, Lieberman IH. Laparoscopic lumbar interbody spinalfusion. Surg Clin North Am 2000; 80:1487–1500.

16. Inamasu J, Guiot BH. Laparoscopic anterior lumbar interbody fusion: a review ofoutcome studies. Minim Invasive Neurosurg 2005; 48:340–347.

17. Thalgott JS, Chin AK, Ameriks JA, et al. Minimally invasive 360 degrees instrumentedlumbar fusion. Eur Spine J 2000; 9(Suppl 1):S51–S56.

18. Bergey DL, Villavicencio AT, Goldstein T, et al. Endoscopic lateral transpsoas approachto the lumbar spine. Spine 2004; 29:1681–1688.

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19. Pimenta L, Diaz RC, Guerrero LG. Charite lumbar artificial disc retrieval: use of a lateralminimally invasive technique. Technical note. J Neurosurg 2006; 5:556–561.

20. Wright N. XLIF—The United States Experience 2003–2004. International Meeting onAdvanced Spinal Techniques, Banff Alberta, Canada, 2005.

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Complications with Use of RecombinantHuman Bone Morphogenetic Protein 2 AfterTransforaminal Lumbar Interbody Fusion

12 Christopher Nanson, Robert Calderon, andKai-Uwe Lewandrowski

n INTRODUCTION

Nowadays, multiple bone graft replacement, extender, and substitute materials areavailable for improving clinical outcomes with spinal fusion procedures.Recombinant human bone morphogenetic protein 2 (rh-BMP-2) has found wideapplication in interbody fusions. It supersedes the use of iliac crest autograft boneas it induces the body to grow its own bone (1–4).

In 2000, the Food and Drug Administration (FDA) approved the use of rh-BMP-2 for anterior interbody fusion when used in conjunction with the LumbarTapered Fusion Device; LT cage� (Sofamor Danek) (5). Since then, Q1clinical studieshave indicated equivalent interbody fusion rates between rh-BMP-2 and iliac crestbone graft (4,6). As a result, rh-BMP-2 has found a number of “off-label”applications, one of which includes its use for posterior interbody lumbarfusions (7).

The BMPs belong to the transforming growth factor super family (8). Theyare involved in the development and differentiation of skeletal tissues, as well asthe brain, spinal cord, liver, kidneys, skeletal muscle, eyes, and epithelium (3,9).Physiologic concentrations of BMP-2 are quite low. Although sufficient for normalfracture healing, only 0.002mg of BMP-2 can be extracted from 1kg of normalpowdered bone (10). To achieve a demonstrable enhancement of fracture healing,much higher BMP-2 concentrations, ranging from 0.01mg/mL in rodents to1.5mg/mL in nonhuman primate models, are necessary. The commerciallyavailable form of rh-BMP-2, Infuse� (Medtronic Sofamor Danek) contains1.5mg/mL of reconstituted collagen sponge (9,11). More recently, even highernumbers have been suggested for posterolateral fusions. Boden et al. foundsuccessful posterolateral lumbar spinal fusion with or without the use of internalfixation when rh-BMP-2 was delivered at a dose of 20mg per side (12). It has beensuggested that only these “supraphysiologic concentrations” are in fact capable ofinducing the desired clinical effect by overcoming the tight regulation of BMP andits inhibitors (8).

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Christopher Nanson and Robert Calderon Department of Orthopaedics, University MedicalCenter, Tucson, Arizona, U.S.A.Kai-Uwe Lewandrowski Department of Orthopaedics, University Medical Center and Center forAdvanced Spinal Surgery, Southwest Orthopaedic Surgery Specialists PLC, Tucson, Arizona, U.S.A.

173

Although the application of rh-BMP-2 is successful in the vast majority ofspinal fusion patients, reports on complications related to its use in posteriorlumbar interbody fusions (PLIFs) are now emerging. Of particular interest areproblems related to vertebral osteolysis, cage migration, BMP leakage from theinterspace into the spinal canal, resulting in spinal stenosis due to excessbone formation, and epidural fibrosis. Therefore, we report on the incidence ofthese problems in our original series of 85 patients who underwent transforaminallumbar interbody fusion (TLIF) for symptoms related to degenerative disc diseaseand spondylolisthesis.

n STUDY DESIGN AND PATIENTS

From November 2004 to January 2007, 83 patients consisting of 53 females and30 males underwent minimally invasive lumbar fusions (TLIF) through 1 inchparaspinal incisions made using the Wiltse approach. Surgical indications includedspondylolisthesis (51 patients), degenerative disc disease resulting in discogeniclow-back pain (30 patients), recurrent herniated nucleus pulposus (2 patients), andadjacent level disease (1 patient). The surgical fusion levels are listed by patientsand total number of levels in Tables 1 and Table 2. The procedures were performedby the senior author.

n COMPLICATIONS

Five of the 83 patients showed signs of vertebral osteolysis postoperatively.Another nine patients had excess heterotopic bone formation in the spinal canal,and six additional patients showed signs of migration of their interbody fusioncage. In our series of 83 patients, the complication rate of the use of rh-BMP-2 inTLIFs was 16.6%. In this chapter, we retrospectively analyze the operative reports,radiographs, and medical records of these 20 consecutive patients to identify anyrisk factors that may predispose patients to these complications.

n INSTRUMENTATION

Seventy-eight patients had bilateral posterior pedicle screw-rod instrumentationwith Pathfinder� titanium implants (Abbott Spine). An additional five patientshad unilateral posterior pedicle screw-rod instrumentation with Pathfindertitanium implants (Abbott Spine) and with ipsilateral percutaneous placement of

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TABLE 1 Surgical Fusions and Patients

Level Patients

L2–L3 1L3–L4 7L3–L5 4L4–L5 30L4–S1 17L5–S1 24Total 83

174 n Nanson et al.

translaminar facet screws (AO Synthes� 4.0 and 4.5mm cannulated partiallythreaded screws). Two types of interbody fusion cages were used in conjunctionwith local bone graft and rh-BMP-2 (Infuse�)), Traxis� cage (Abbott Spine) madefrom polyetheretherketone (PEEK), and Saber� cage (Depuy Spine) made fromcarbon fiber.

n SURGICAL TECHNIQUE

Bilateral or unilateral Wiltse-type muscle-splitting approaches were used toperform the TLIF and to place the pedicle screws. In general, the TLIF wasperformed through the side on which the patient’s radicular symptoms were moresevere. This involved removal of the entire facet joint, discectomy, and endplatepreparation. Prior to inserting the interbody fusion cage, approximately 1.5 to 2 ccof morselized local bone graft and one Infuse� collagen sponge were placed intothe interspace. This was followed by insertion of one interbody fusion cage, whichwas filled with an additional Infuse� collagen sponge and local bone graft. Cageposition was checked under biplanar fluoroscopy to assure anterior position acrossthe midline. Then, Gelfoam was injected into the disc interspace and thefacetectomy site to minimize postoperative blood loss and leakage of rh-BMP-2into the neuroforamen. It was removed by suction prior to wound closure.

n rh-BMP-2 Dosage

In this entire series of 83 patients, only small and medium kits with two and fourabsorbable collagen sponges (ACS; 100 � 200) were used. These kits come with a4.9mg vial of rh-BMP-2. According to the manufacturer, only 4.2mg of the 4.9mgof rh-BMP-2 are applied to the ACS following reconstitution.

n POSTOPERATIVE CARE

Postoperatively, mobilization began as soon as it was tolerated by the patient,either immediately postoperatively or on postoperative day 1, with formal gaittraining by the physical therapist. Most patients were discharged to their home onpostoperative day 1. None of the patients received any lumbar supports or braces.Low-impact exercising, walking to tolerance, and swimming was encouragedimmediately upon the patient’s discharge to home. Heavy lifting and any othertype of strenuous activity were discouraged for at least six weeks postoperatively.Patients were otherwise permitted to return to work as soon as they could tolerateit. All patients were counseled to avoid over-the-counter nonsteroidal anti-inflammatory medications during the first six weeks postoperatively.

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TABLE 2 Surgical Fusion Levels

Level Patients

L2–L3 1L3–L4 11L4–L5 51L5–S1 51Total 104

Q2

Complications with Use of Recombinant Human n 175

n VERTEBRAL OSTEOLYSIS

Five of the 83 patients who underwent PLIF via the transforaminal approachdeveloped osteolysis of the L5 vertebral body (Table 3). The average age of thesefive patients was 50.2 years. They consisted of three males and two females. Noneof these patients had any significant medical comorbidities. Two of the five patientscontinued to smoke after surgery in spite of preoperative counseling.

Four of the five patients underwent L5–S1 TLIF for single-level disease.A representative case is shown in Figure 1. These four patients had PEEK cagesand two 100 � 200 ACS from a small Infuse� kit placed into the intervertebral discspace. These two ACS were reconstituted with 4.2mg rh-BMP-2 of the 4.9mg vial.The remaining patient had revision surgery for adjacent level disease at L5–S1 andnonunion at L3–L4 after a previous L3–L5 posterior spinal fusion with aninterbody fusion cage at L4–L5. She underwent removal of implants andreinstrumentation with placement of PEEK interbody fusion cages at L3–L4 andL5–S1 via the TLIF approach (Fig. 2). This patient had a total of four 100 � 200 ACSfrom a medium Infuse� kit placed into the intervertebral disc space. These fourACS were reconstituted with 4.2mg rh-BMP-2 of the 4.9mg vial.

All five patients had degenerative disc disease with significant loss of height,osteophyte formation, and sclerosis of the endplates. In order to facilitatedistraction for placement of a sizable interbody fusion cage, distracting paddleshavers were used to mobilize the L5–S1 interspace. The paddle shavers wereplaced as far as possible anteriorly to achieve distraction of the anterior vertebralbody rim. This was done in an effort to minimize violation of the endplates. In eachof the five patients, the height of the interbody fusion cage was no more than 9mm.Each cage was trailed prior to insertion of the final implant.

Each of these five patients did well initially until presenting with new onsetsevere low-back pain. Their symptoms appeared anywhere between four weeksand three months postoperatively. None of the five patients demonstrated anysignificant radicular symptoms. Typically, symptoms resolved with supportivenonoperative care within three months from their onset. A CT scan was obtained.To our surprise, resorption of the inferior aspect of the L5 vertebral body hadoccurred in each of these five patients. There was one medially placed S1 pediclescrew in one patient. However, this patient did not have any evidence of S1radiculopathy and his acute low-back pain resolved within an additional twomonths from its onset. Six months after his acute episode had resolved, the patient

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TABLE 3 Patients with Vertebral Osteolysis

No. Sex Age Preop diagnosis Procedure Previous surgery

1 F 50 L5–S1 adjacent leveldisease

L3–S1 TLIF L3–L5 PSF, L4–L5PLIF

2 M 50 L5–S1 spondylolisthesis L5–S1 TLIF

3 M 50 L5–S1 spondylosis L5–S1 TLIF

4 F 50 L5–S1 spondylosis L5–S1 TLIF

5 M 51 L5–S1 spondyolisthesis L5–S1 TLIF

Abbreviations: PSF; PLIF, posterior lumbar interbody fusion; TLIF, transforaminal lumbar interbody fusion. Q3

176 n Nanson et al.

developed symptoms related to prominent spinal instrumentation with increasingactivity. He improved with several trigger-point injections and physical therapy.He underwent removal of the pedicle screws nine months postoperatively.Histological microsection of a transpedicular biopsy of the osteolytic area showedbenign-appearing trabecular bone with small fragments of granulation tissuewithout evidence of osteomyelitis (Fig. 3).

n MIGRATION OF INTERBODY FUSION CAGES

Six of the 83 patients who underwent PLIF via the transforaminal approachshowed signs of migration of their interbody fusion cage (Table 4). The average ageof these five patients was 55.2 years. They consisted of one male and five females.None of these patients had any significant medical comorbidities.

Two of the six patients underwent L4–L5 TLIF for single-level disease with asingle PEEK cage and two 100 � 200 ACS from a small Infuse� kit placed into theintervertebral disc space. These two ACS were reconstituted with 4.2mg rh-BMP-2of the 4.9mg vial. Three patients had an L4–S1 TLIF with single PEEK cages andtwo 100 � 200 ACS from a small Infuse� kit placed into the intervertebral disc space.The remaining patient had an L3–L5 TLIF with a similar PEEK and BMP fusion asthe other patients.

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FIGURE 1Anterior-posterior and lateral radiographs of a 50-year-old woman who

underwent L5–S1 TLIF (A,B). Similar X rays taken three months after the index procedurewere suggestive of osteolysis in the L5 vertebral body (C,D). A CT scan confirmedosteolysis around the interbody fusion cage involving the inferior part of the L5 vertebralbody (E,F). At six months postoperatively, her symptoms had resolved. Abbreviation: TLIF,transforaminal lumbar interbody fusion.


While all six patients had complete resolution of their originalsymptoms after the index procedure, they presented with recurrent low-backand leg pain between two to six months postoperatively. Cage migration wasdiagnosed on the basis of plain films, MRI, and CT scans that were promptedby the patients’ new onset acute low-back and leg pain. These studiesrevealed posterior-lateral migration of the interbody fusion cage with somebone resorption around the cage. In four cases, cages encroached on theexiting and traversing nerve root. In an additional two cases, neural elementswere clearly Q4displaced.

At the time of writing this chapter, three of the six patients failedconservative management and underwent formal open revision surgery. Inone patient, it was feasible to remove the interbody fusion cage from aposterior PLIF-type approach. In the remaining two patients, cage removalwas not possible because of extensive epidural fibrosis and excessive boneformation around the cage. Therefore, the cage was left in place in these twopatients and a very wide decompression was performed to adequatelydecompress the neural elements. All three patients who underwent surgicalrevision for dislocated cages with rh-BMP-2 improved significantly post-operatively. Radicular symptoms did resolve in all three patients. Resolutionof low-back pain was less predictable.

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FIGURE 2CTscans of the lumbar spine of a 50-year-old woman following L3–S1 TLIF with

placement of rh-BMP-2 and an interbody fusion cage at L5–S1. The patient presented withsevere low-back pain 10 weeks after her surgery at which time saggital (A) and coronal (B)CTscans confirmed osteolysis. Similar scans obtained six months postoperatively showedat least partial reconstitution of the osteolytic defects (C and D). This patient’s symptomseventually resolved without further treatment. Abbreviations: TLIF, transforaminal lumbarinterbody fusion; rh-BMP-2, recombinant human bone morphogenetic protein 2.

178 n Nanson et al.

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FIGURE 3Histopathologic photomicrograph (4�) of a transpedicular biopsy of an osteolytic

lesion of L5 obtained during routine hardware removal. The specimen was taken from a50-year-old who previously underwent L5–S1 TLIF with placement of rh-BMP-2 and aninterbody fusion cage. The lesion had healed with formation of trabecular bone (B). Asshown in the inset (10�), granulation tissue (G) was found in close proximity to thetrabecular bone. Abbreviations: TLIF, transforaminal lumbar interbody fusion; rh-BMP-2,recombinant human bone morphogenetic protein 2.

TABLE 4 Patients with Dislocated Interbody Fusion Cage

No. Sex Age Preop diagnosis ProcedurePrevioussurgery

Level of cagedislocation

1 M 52 L4–S1spondylolisthesis

L4–L5TLIF

L5–S1

2 F 70 L4–L5spondylolisthesis

L4–L5TLIF

L4-5 lami L4–L5

3 F 47 L4–S1spondylolisthesis

L4–S1TLIF

L4–L5 lami�4

L4–L5


L4–S1TLIF

L4–L5


L4–S1TLIF

L5–S1

6 F 82 L3–L5spondylolisthesis

L3–L5TLIF

L4–L5microdisc

L3–L4;L4–L5



n HETEROTOPIC BONE FORMATION IN THE SPINAL CANAL

Nine of the 83 patients who underwent PLIF via the transforaminal approachpresented with heterotropic bone formation in the spinal canal (Table 5). Theaverage age of these five patients was 51.1 years. They consisted of six males andthree females. None of these patients had any significant medical comorbidities.Three of the nine patients continued to smoke after surgery in spite of preoperativecounseling.

Five of the nine patients underwent L5–S1 TLIF for single-level disease with asingle PEEK cage and two 100 � 200 ACS from a small Infuse� kit placed into theintervertebral disc space. These two ACS were reconstituted with 4.2mg rh-BMP-2of the 4.9mg vial. An additional three patients had an L4–S1 TLIF with singlePEEK cage and two 100 � 200 ACS from a small Infuse� kit placed into theintervertebral disc space. These four patient had a total of four 100 � 200 ACS from amedium Infuse� kit placed into the intervertebral disc space. These four ACS werereconstituted with 4.2mg rh-BMP-2 of the 4.9mg vial. The remaining one patienthad an L4–L5 TLIF with the same implants and rh-BMP-2 dosage as the patientswho underwent L5–S1 TLIF fusion.

All nine patients had complete resolution of their original radicularsymptoms after the index procedure. Seven of the nine patients had recurrentradicular symptoms between six to nine months postoperatively, which promptedtheir work-up with CT and MRI scans. These studies revealed recurrent foraminalstenosis, which was attributed to heterotopic bone formation in the spinal canalencroaching on the exiting and traversing nerve root. The additional two patientswere diagnosed on the basis of CT scans that were taken for other reasons.

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TABLE 5 Patients with Heterotopic Bone Formation in the Spinal Canal

No. Sex Age Preop diagnosis ProcedureLevel and effect of excess

bone formation

1 M 56 L4–S1spondylosis

L4–S1 TLIF L4–L5; L5 radiculopathy


L4–S1 TLIF L4–L5; L5 radiculopathy

3 F 36 L4–S1spondylosis

L4–S1 TLIF L5–S1; S1 radiculopathy


L4–L5 TLIF L4–L5; L5 radiculopathy












180 n Nanson et al.

Patients’ symptoms were managed conservatively with physical therapy andtransforaminal epidural steroid injections. In six of the nine patients, symptomsresolved with this supportive nonoperative care within two to six weeks of theironset. In three patients, attempts at conservative management were unsuccessful,and they underwent formal revision laminectomy and foraminotomy through amidline approach. Attempts were made to remove the excess bone directlycompressing neural elements. All three patients had complete resolution of theirradicular symptoms after their revision surgery.

n DISCUSSION

rh-BMP-2 is now widely used for posterior interbody fusions. Its use seemsparticularly advantageous when employed in conjunction with minimally invasiveaccess techniques, as it obviates the need for a separate incision for iliac crest boneharvest and its well-recognized morbidities including persistent pain, prolongedoperation room time, and increased blood loss.

Reports of high fusion rates reported with the use of rh-BMP-2 inanterior lumbar interbody fusion (ALIF) have led to the expansion of itsclinical use beyond the FDA-approved application for ALIF with the LT cage(5). Recent clinical evidence suggests that application of rh-BMP-2 in posteriorinterbody fusion is as effective as TLIF procedures performed with the use ofiliac crest autograft (7).

This case series of 83 patients who underwent a TLIF procedure with rh-BMP-2 shows that the clinical use of this recombinant osteoinductive protein as anadjunct to posterior interbody spinal fusion can be associated with significantcomplications. Our clinical complication rate was 16.6% and 20 of 83 patients hadclinically symptomatic problems related to the use of rh-BMP-2. Specifically, fivepatients had vertebral osteolysis, nine patients had excess bone formation in thespinal canal, and an additional six patients dislocated their interbody fusion cage.Six of these 20 patients required revision surgery less than one year from theirindex procedure (three patients for migrated interbody fusion cages, and threepatients for excess bone formation in the spinal canal).

This retrospective case study on the use of rh-BMP-2 for transforaminalinterbody fusion is unique is several ways. First, the three reported problemsoccurred at different times in the postoperative period.

Second, there was a specific association with certain spinal motion segments.Third, the magnitude of the clinical symptoms was quite variable. Finally,management was quite distinct and dictated by the severity and persistence ofsymptoms.

For example, osteolysis occurred only at the L5–S1 motion segment andpatients became symptomatic between 6 and 12 weeks postoperatively. Cagemigration occurred between two and six months postoperatively, and excess boneformation in the spinal canal became symptomatic between six and nine monthspostoperatively.

Overall, the clinical presentation of these complications was variable induration and length of time from surgery, making assessment of their trueprevalence difficult. In fact, other patients in our original series of 83 may have hadvertebral osteolysis, excess bone formation in the spinal canal, or migration of theinterbody fusion pain without clinical symptoms.

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The clinical management was quite distinct as well. All five patients showedcomplete resolution of their symptoms within 12 weeks of their onset. Asillustrated in Figure 2, follow-up CT studies appeared to show at least partialreconstitution of the cavernous defects and it seemed that these defects wouldeventually go on to heal themselves without aggressive intervention. On the otherhand, cage migration and excess bone formation required surgical revision in threecases each.

Although there is no conclusive evidence to suggest any definitive cause,vertebral osteolysis and cage migration appear to be interrelated since cagemigration was always accompanied by bone resorption. Three possible explana-tions appear reasonable. First, violation of the endplates with paddle shavers anddilators during the interbody fusion may have occurred. This seems more probableat the lower lumbar motion segments, such as the L5–S1 level, than at any otherlumbar level because of the higher inclination of the interspace. During endplatepreparation, excessive decortication through the subchondral bone of the endplatemay have exposed bleeding cancellous bone from within the vertebral body to the

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FIGURE 4Saggital CT scan of the lumbar spine of a 33-year-old woman 12 months

following L5–S1 TLIF with placement of rh-BMP-2 and an interbody fusion cage at L5–S1.The patient presented with recurrent S1 radiculopathy eight months after her surgery atwhich time saggital CT images showed excess bone formation in the spinal canal (whitearrow). She failed conservative management and went on to have a formal revisiondecompression. Abbreviations: TLIF, transforaminal lumbar interbody fusion; rh-BMP-2,recombinant human bone morphogenetic protein 2.

182 n Nanson et al.

rh-BMP-2. Results of the histopathological evaluation of the transpedicular biopsyin one patient with vertebral osteolysis showed trabecular bone and granulationtissue without evidence of infection, suggesting the presence of an inflammatoryprocess in the healing osteolytic defect.

Heterotopic bone formation within the spinal canal may simply be the resultof leakage of rh-BMP-2 from the interspace. Poynton and Lane (13) and McKay andSandhu (14) have noted heterotopic bone growth into the spinal canal and neuralforamina, prompting them to abort a study using cages in a PLIF approach owingto bone formation along the track of cage insertion and within the spinal canal(13,14). Patel et al. have recently reported on the utility of fibrin glue to prevent

501502503504505506507508509510511512513514515516517518519520521522523524525526527528529530531532533534535536537538539540541542543544545546547548549550

FIGURE 5CTscans of the lumbar spine of a 36-year-old woman following L4–S1 TLIF with

placement of rh-BMP-2 and an interbody fusion cage at L4–L5 and L5–S1. The patientpresented with recurrent L5 and S1 radicular symptoms eight months after her surgery atwhich time axial (A,B) and saggital (C) CT scans showed posterior dislocation of theinterbody fusion cage at L5–S1. In addition, excess bone formation into the spinal canalwith recurrent neuroforaminal stenosis was seen at L4–L5 and at L5–S1. Abbreviations:TLIF, transforaminal lumbar interbody fusion; rh-BMP-2, recombinant human bonemorphogenetic protein 2.


leakage into the spinal canal (15). They determined that fibrin glue appears to limitthe diffusion of BMP from the rh-BMP-2 soaked sponges without binding to it.Patel et al. suggested that fibrin glue could be used “to separate the areas of desiredbone formation from areas where bone formation is not desired” (15).

Therefore, “overstuffing” of the interspace may have contributed to the threetypes of complications as well. Although it has been suggested that higher doses ofrh-BMP-2 are required for posterolateral intertransverse fusions, it seems entirelypossible that doses smaller than the 1.5mg/mL of reconstituted collagen spongecontained in Infuse� are sufficient to induce successful interbody fusions. Finally,dose-dependent cellular cascade activation of osteoclasts and osteoblasts may haveoccurred due to the rh-BMP-2–induced inflammatory effects that were recentlydiscussed in the pathogenesis of its adverse effects in anterior spinal fusion (16,17).

This retrospective case series shows that use of rh-BMP-2 as an adjunct toPLIFs may result in significant clinical complications. Violation of the endplatesduring decortication, overstuffing of the interspace, and leakage of the rh-BMP-2may be contributing factors. Patients may improve without operative interventionand symptoms may resolve spontaneously. However, operative intervention maybe necessary in some cases.

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23. Suh DY, Boden SD, Louis-Ugbo J, et al. Delivery of recombinant human bonemorphogenetic protein-2 using a compression-resistant matrix in posterolateral spinefusion in the rabbit and in the non-human primate. Spine 2002; 27(4):353–360.

24. Barnes B, Boden SD, Louis-Ugbo J, et al. Lower dose of rhBMP-2 achieves spine fusionwhen combined with an osteoconductive bulking agent in non-human primates. Spine2005; 30(10):1127–1133.

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Adjacent Level DegenerationFusion Techniques

13 Christopher M. Bono

n INTRODUCTION

With recent technological advancements, the deleterious effects of adjacentsegment degeneration (ASD), also known as adjacent level disease, in the lumbarspine have commanded increasing interest in recent years (1–8). Motion-sparingtechnology aims to lessen the stresses placed on adjacent motion segments, whichconceptually might decrease the chances of ASD. Minimally invasive surgery(MIS) takes a more indirect path of attack on ASD by minimizing the potentiallydestabilizing effects of a midline, muscle-stripping posterior exposure. Althoughthere are clear short-term benefits such as hastened rehabilitation and shorterhospital stays, the long-term effectiveness of MIS in lowering the rate of ASDremains hypothetical. In stark contrast is the trusted reality that ASD can, and will,cause substantial disability and dysfunction in many patients following lumbarfusions.

The certainty of facing a patient with ASD calls upon spine surgeons to beadept at its work-up and management. This is aided by an understanding of thosesurgical variables thought to be predisposing factors for ASD. Ultimately, thedecision to perform revision surgery is based on the symptoms’ impact on functionand quality of life. As various options exist, operative decision-making is guidedby a variety of factors such as the underlying pathology, extent of disease, and hostbone quality.

n BACKGROUND: SURGICAL INFLUENCES ON ASD

Perhaps the seminal article on ASD was published by Lee (6) in 1988. In 18 of hispatients, he described the development of symptomatic degenerative changes at anonfused level adjacent to various forms of lumbar fusion. These included axialback pain from severe disc degeneration, facet joint arthritis, spinal stenosis, ornew-onset spondylolysis. With this, surgeons developed a greater awareness of thephenomenon. Only recently have studies documented the rate of ASD, which hasvaried widely, from 0% to 100% (4,9–14).

There are a number of surgical factors thought to influence the developmentof ASD. In an excellent review of the literature, Park et al. (15) compiled a list ofpotential risk factors in degenerative cases. These included posterior lumbarinterbody fusion (PLIF), pedicle screw insertion, increasing fusion length, sagittal

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Christopher M. Bono Department of Orthopaedic Surgery, Boston University Medical Center,Boston, Massachusetts, U.S.A.

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malalignment, preexisting disc degeneration, lumbar stenosis, age, osteoporosis,female gender, and a postmenopausal state (15). Individual studies have suggestedcertain factors as being more or less important (4,5,9,10,16–18). Of interest to thepresent discussion are those that are surgically controllable, such as the fusionmethod, fusion length, alignment, and use of pedicle screws. Other factors thathave been recently cited but lack literature support are related to the use of aposterior approach and include injury to the facet joints, midline ligaments, andparaspinal muscles.

It must be understood that radiographic presence of ASD does not obligatethe patient to be symptomatic. In a recent publication, Hilibrand and Robbins (19)called for a distinction between ASD (a radiographic finding) and adjacentsegment disease, which is the clinical sequela variably present with degeneration.Most studies have demonstrated little association between a poor clinical outcomeand the presence of radiographic ASD (5,14,20). Notwithstanding this trend,individual cases can produce symptoms (6). Many studies have used the need foradditional surgery as a clinical marker of symptomatic ASD (4,21). It is not certainwhich predisposing factors might increase the chance of symptoms from ASD.

n DIAGNOSTIC WORK-UP

HISTORY AND EXAMDeciphering the origin of pain and symptoms in a patient who has had previousfusion can be challenging. History-taking is of critical importance, as it guides theinterpretation of imaging findings as well as treatment. Most patients have acomplaint of back pain. However, this complaint is often vague and nondescript.The region or regions of pain should be localized. Patients indicating diffuse painthat is primarily in the low paraspinal muscle region might be experiencingmuscular fatigue rather than pain from mechanical instability. This is commonwith flat-back deformities or other disorders that result in an anterior shift of theweightbearing axis.

Unilateral, paraspinal pain that is localized to one level is more suggestive offacet-mediated pain. This can occur from facet degeneration, impingement of thefacet joint by a screw or rod, or a de novo spondylolysis (pars fracture). Pain inthese cases may be exacerbated by extending the back and relieved by flexingforward. Midline axial pain that radiates bilaterally and is exacerbated with flexionis much more indicative of discogenic pain. Finally, exercise-induced back painthat occurs primarily with walking and resolves with rest is likely a presentation ofneurogenic claudication from spinal canal narrowing; such patients are unlikely tohave much tenderness upon palpation of the back.

RADIOGRAPHIC WORK-UPThe radiographic hallmarks of adjacent level disc degeneration include disc spacenarrowing, endplate sclerosis, and osteophyte formation. Often, facet degenerationis noted by overgrowth and sclerosis of the joint surfaces. This may be difficult toappreciate with pedicle screws in place, as they abut the most distal portions of theunfused cranial joint.

ASD can lead to (or be the result of) an abnormal alignment of the lumbarspine. On a lateral radiograph, antero- or retrolisthesis of the unfused vertebralsegment should be noted. The amount of translation is measured by comparing the

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188 n Bono

distance between the posterior vertebral body tangent lines (Fig. 1A–C). Low-grade slips (< 5mm) are likely from facet and/or disc incompetence. Higher-gradeslips are more likely the result of a de novo pars fracture (i.e., an isthmic-typespondylolisthesis).

The overall alignment and balance of the previously fused and unfusedsegments should be observed. It is important to differentiate fixed deformities fromdynamic ones. In the adult degenerative population, most coronal plane (scoliotic)deformities are rigid, so that side-bending films may not be very helpful. Assagittal plane deformities (kyphosis or listhesis) are often mobile, dynamicflexion–extension views can be useful in planning correction maneuvers and/orthe extent of the fusion.

Beyond plain radiographs, MRI should be obtained. This is the imagingmodality of choice to assess the patency of the spinal canal and neuroforaminae. Incontrast to CT, the nerve roots in the foramina and within the cauda equina can be

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FIGURE 1Static lateral or flexion–extension views can be used to measure the amount of

translational deformity present. This is best assessed by drawing a line tangent to thevertebral bodies of the motion segment. This can be done in the neutral (A), flexion (B),and extension (C) views. The transverse distance between the posterior vertebral marginsdenotes the amount of translation.

Adjacent Level Degeneration Fusion Techniques n 189

directly visualized, as well as the compressive pathology that may be impingingupon them. The condition of the intervertebral disc should also be scrutinized.Although the adjacent disc may be obviously degenerated on plain films, an MRIcan demonstrate less-profound degenerative changes in the next most suprajacentdisc (Fig. 2). This can influence the decision to include such a level in the revisionfusion construct as it is likely to undergo more rapid degenerative progressionwith continued motion.

While MRI readily reveals degeneration of the facet joints, CT is slightly moresensitive (22,23). Axial images are generally more useful than coronal or sagittalreconstructions. CT is substantially more sensitive than MRI at detectingspondylolytic defects (24). Like MRI, sagittal reconstructions can help appreciate

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FIGURE 2Sagittal T2 MRI of a patient who had undergone an L4 to S1 fusion several years

prior to presentation. Although the initial fusion was performed with pedicle screws, theinstrumentation had been subsequently removed, and exploration demonstrated a solidfusion. The patient presented with symptomatic low-back pain with lower extremityclaudicant pain from a de novo spondylolisthesis at the next most suprajacent level(L3–L4). The MRI clearly demonstrates advanced degenerative changes at that level. Inaddition, early changes at the L2–L3 are appreciated, as the signal intensity of the nucleusappears to be slightly diminished compared to the other proximal disc levels.

190 n Bono

the effects of listhesis or osteophyte encroachment on the spinal canal and neuralforamen. However, the neural elements are more difficult to visualize. A CTmyelogram can improve upon this deficiency, though it carries the additional riskand morbidity of an intradural contrast injection. Furthermore, extradural neuralpathology can be missed, such as foraminal or extraforaminal nerve rootcompression. Notwithstanding its disadvantages and limitations, CT myelographyis a viable advanced imaging alternative for patients in whom MRI is contra-indicated (e.g., those with pacemakers or internal defibrillators) or in whomartifacts from ferromagnetic spinal implants (e.g., stainless steel pedicle screws)would preclude useful images.

n PREOPERATIVE PLANNING

Making the decision to perform a revision operation for ASD can be a difficult one.To optimize results, a clear primary source of pain should be identified. In asimplistic list, this includes a degenerated disc, facet arthritis, dynamic instability,fixed deformity, and neural compression. One or more may be causing pain in asingle patient. Likewise, one or more may be clinically silent as it may represent aradiographic finding only.

Consider the following case example. A patient presents with a grosslydegenerated adjacent cranial level with mild canal stenosis. Symptoms includemechanical, axial back pain that is localized to the degenerated level without anyneurogenic claudicant pain or lower extremity radiculopathy. Physical examina-tion reveals tenderness upon palpation only at that level. After failure ofappropriate nonoperative measures, preoperative planning would focus on thedegenerative disc as the primary source of pain and dysfunction. Thus, fusion andstabilization of this level would be planned. Even in the setting of mildradiographic stenosis, laminectomy would not have been performed in theauthor’s practice. A laminectomy incurs additional risk to the nerves and caudaequina, which, clinically, are asymptomatic and performing normally in this case.In addition, maintaining the laminae can increase the available surface area forfusion. With the same radiographic findings, a laminectomy would be planned ifthe patient had significant lower extremity pain that could be correlated to thesite(s) of neural compression.

ASD often occurs adjacent to a level fused with pedicle screws. Usually,instrumentation will be extended proximally or distally to include additionalsegments. This requires removal of the longitudinal member (rod or plate) with orwithout removal of the screws, depending on their quality of fixation. Theappropriate removal/insertion tools should be available to facilitate thesemaneuvers. With an extensive knowledge of the radiographic appearance ofvarious instrumentation systems, the correct manufacturer and screw system canusually be deduced. However, the most reliable information is contained in theoriginal operative record.

Knowing the diameters of the screws prior to surgery can also be helpful. Toavoid placing too large a diameter screw during revision surgery, the surgeon mayplan to place new screws that are only slightly larger. For example, if the screws tobe explanted are 6mm in diameter and the next largest screw in the same system isa 7mm screw, then the surgeon may plan to insert 6.25 or 6.5mm screws from adifferent manufacturer’s system. Importantly, this would require removal of all

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preexisting screws if a same-diameter rod could not be used. In general, it is theauthor’s preference to utilize variable-angle screws, particularly in a revisionsituation, as reducing the rod into the screw heads is less cumbersome than withfixed-angle devices.

The surgeon may also anticipate encountering a stripped screw-lockingdevice, such as the internal hex of an interference screw (i.e., lock nut). This canpreclude removal of the rod from the screw head. A metal-cutting bit for a high-speed burr can be used to cut the rod between the screws. The short fragment ofrod may then be used to rotate the screw for removal. Although minimal accessscrew removal using tubular retractors has been recently reported (25) and iscertainly possible with ASD, such techniques may not be preferred if additionalsurgery including open exploration of a previous fusion is planned.

Loss of lordosis (i.e., relative kyphosis) of the adjacent segment is animportant variable to consider during preoperative planning. As this has beenidentified as a potential contributing factor to ASD, it may be desirable to correctsuch misalignments. Notwithstanding profound multiplanar deformities (thetreatment of which lies outside the scope of this chapter), kyphosis is mostcommonly localized to the adjacent degenerated segment. Flexion–extension viewscan demonstrate if it is fixed or mobile. If the spine corrects to an acceptablealignment with full extension, a simple posterior instrumented fusion can beeffective in achieving and maintaining correction (provided that the disc itself neednot be excised for pain relief).

If the deformity is fixed, an interbody release might be preferred. A PLIF, orits close cousin, transforaminal lumbar interbody fusion (TLIF), can effectivelyrestore some disc-space height. Provided that the disc space can be distractedenough, sagittal alignment can be controlled by varying the geometry and locationof the interbody device and the amount of posterior compression applied to thepedicle screws before final tightening (Fig. 3A– C). If the endplates appear toconverge anteriorly and/or there is substantial osteophyte formation along theanterior vertebral bodies, a PLIF or TLIF may be less effective. In these cases, ananterior lumbar interbody fusion (ALIF) can facilitate resection of the osteophytes,release of a contracted anterior longitudinal ligament (ALL), and placement of alordotically shaped interbody device (Fig. 4A). Posterior stabilization is usuallyadded in the setting of ASD (Fig. 4B).

n SURGICAL OPTIONS: DECOMPRESSION

LAMINOTOMY AND FORAMINOTOMYASD can sometimes result in symptomatic unilateral radiculopathy from foraminalor lateral recess stenosis. The offending pathoanatomical features can includeposterior protrusion of the disc (rarely a true disc herniation), posterior vertebralbody osteophytes, or arthritic facet overgrowth (Fig. 5). Facet hypertrophy can leadto foraminal stenosis (directly anterior to the facet) or lateral recess stenosis (medialor anteromedial to the facet). The former can lead to compression of the exitingnerve root, while the latter is more likely to involve the descending nerve root.

Provided that central stenosis or bilateral lateral recess stenosis is not present,which would require a more extensive decompression, a laminotomy andforaminotomy is indicated for the treatment of unilateral leg pain from rootcompression at a segment adjacent to a previous fusion. The complexity of the

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surgery is dependent on the nature of the previous operation. If a laminectomy hadbeen performed at that level or the level below, the surgeon must carefully separatethe scarred dura from the bony borders of the hemilamina to be removed.

If the posterior elements were never violated or removed, then the procedureis essentially virgin and can proceed in the usual manner. The ligamentum flavumis released from the inferior border of the level above, superior border of the levelbelow, and medial to the facet joint. A Kerrison rongeur is then used to remove thenecessary portions of the lamina and facet joint to gain full access to the foramen.The facet joint is undercut as needed to ensure root decompression. By gentlyretracting the neural elements toward the midline with a nerve root retractor orPenfield elevator, the posterior aspect of the disc space can be inspected. Ifposterior vertebral body osteophytes or disc protrusion are thought to be offendingelements, they can be removed at this time.

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FIGURE 3With a TLIF, the degree of segmental lordosis can be controlled by varying the

location of the interbody device and the amount of compression applied. With cylindricalmesh cages in the mid-aspect of the intervertebral space (A), a moderate amount oflordosis can be achieved. With the cages placed far anterior (B), a larger amount oflordosis can be achieved. Placing the cages in the posterior aspect of the disc space (C)yields the least amount of possible lordosis as it is limited by the tension band effect of theanterior annulus and ALL. Abbreviations: ALL, anterior longitudinal ligament; TLIF,transforaminal lumbar interbody fusion.


Presumably, foraminal stenosis with ASD is a motion-related phenomenon. Itis the continued abnormal motion at the degenerated segment that has led to thepathological changes (facet hypertrophy, listhesis, or disc protrusion) that in turnare causing radicular compression and irritation. Even in those patients in whomleg pain is the solitary complaint, the author prefers to include fusion of thedecompressed segment for this reason.

Role of MIS TechniquesWhen possible, MIS techniques can be utilized. The ideal candidate would be apatient with unilateral radiculopathy with foraminal stenosis that has not had any

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FIGURE 5Foraminal stenosis and exiting nerve root impingement from ASD can be the

result of posterior disc protrusion, posterior vertebral body osteophytes, or anterior facetovergrowth. Abbreviation: ASD, adjacent segment degeneration.

(A) (B)

FIGURE 4An anterior approach to the disc space can enable maximal correction of

kyphosis/restoration of lordosis. Anterior osteophytes can be removed and a largelordotically shaped graft can be inserted (A). A gentle amount of posterior compressioncan be applied through pedicle screws to lock the graft into place (B).

194 n Bono

previous decompression and has intact posterior elements. In such cases, alaminotomy and foraminotomy can be performed using tubular retractors througha paraspinal muscle-splitting approach. As fusion is usually performed in thesetting of ASD, posterior fusion stabilized with percutaneous insertion of pediclescrews can be performed. Note that this is advised only if the previous fusion issolid and no instrumentation was used or needs to be removed.

LAMINECTOMYA full laminectomy is indicated in those cases of ASD in which there is substantial,symptomatic central canal or bilateral lateral recess stenosis. Typically, patientspresent with worsening low-back pain and lower extremity claudication. Theoffending pathoanatomical features can include overgrown facet joints, infoldedligamentum flavum, and posterior disc or endplate protrusion into the spinalcanal. Foraminal stenosis is often, but not always, concomitantly present.

The most common clinical scenario is that of ASD that develops above thelevel of a previous laminectomy. As discussed above, a contributing factor may bethe resection of the posterior midline ligaments during laminectomy. Importantly,one should recognize, for example, that if a full L4 laminectomy is performed forL4–L5 stenosis with spondylolisthesis, then the interspinous ligaments betweenL3–L4 and L4–L5 must be obligatorily resected. Therefore, an L4–L5 fusion canplace undue stress on the partially destabilized L3–L4 motion segment over time.Depending on the condition of the L3–L4 disc at the time of index surgery, onemight include this level in the fusion. Alternatively, decompression can be limitedfrom the inferior aspect of L4 to the superior aspect of L5, while being careful tomaintain the adjacent interspinous ligaments.

As with laminotomy and foraminotomy, the complexity of the procedure isdependent on the extent of previous surgery. Revision laminectomy requirespatience to adequately release the adherent dura from all bone surfaces to beremoved. Incidental dural tears occur with higher frequency during revisioncompared to primary operations (26).

Role of MIS TechniquesAs an alternative to a full laminectomy, a less-invasive technique of bilateralsubarticular decompression has been described (27). Although the author has notused this technique, it is theoretically possible in the absence of epidural scar. Itinvolves a unilateral resection of the hemilamina and portion of the facet joint.Using the ligamentum flavum as a protective layer, the contralateral canal andforamen are decompressed by undercutting the bone. In its final stages, the flavumis removed and decompression of the contralateral foramen is confirmed. Thepotential advantage of this technique is preservation of the midline ligamentswhile achieving bilateral decompression. Considerations for fusion are similar tothose described above for laminotomy and foraminotomy.

n SURGICAL OPTIONS: FUSION AND STABILIZATION

NONINSTRUMENTED POSTEROLATERAL FUSIONA simple posterolateral fusion without instrumentation is a viable option in somecases of ASD. Although it is an unusual clinical scenario, the author’s indicationfor this procedure includes fusion following a laminotomy and foraminotomy in a

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patient who has minimal or no mechanical back pain. In these cases, fusion isadded to the selective decompression under the assumption that continued motionwould lead to recurrence of foraminal stenosis. An additional proviso is that thedisc space is less than 50% of its anticipated height and lacks any substantialangular deformity.

In most cases, fusion to an adjacent degenerated segment is preceded by anexploration of the previous fusion. Although plain radiographs, CT, orflexion–extension views may be highly suggestive of a solid fusion, their limitedsensitivity in accurately predicting pseudarthroses has been well established(28–30). Open surgical exploration remains the gold standard for assessing aposterolateral lumbar fusion (28,31). Pseudarthroses should be decorticated downto a bone-bleeding surface, and additional bone graft should be packed into thedefect. In addition, one might consider insertion of instrumentation at thenonunited level in order to increase the chance of fusion. The rationale for thesetechniques are discussed below.

The availability of autograft is another important issue. In patients with ASD,it is likely that large amounts of autograft have already been harvested from one orboth of the posterior iliac crests. Although graft from the anterior crests or fibulamay be considered, its harvest adds significant morbidity and time to theoperation, as the grafts are best taken in a supine or lateral position. Alternativesinclude the use of fresh frozen allograft augmented with one of the variouscommercially available demineralized bone matrix preparations. Recently, bonemorphogenic protein-7 (BMP-7), commercially called OP-1 (Stryker Biotech,Rutherford, NJ), has been approved for revision lumbar fusions. Unfortunately,recent data suggest that addition of OP-1 to iliac crest autograft offers noadvantages (32). It is unknown if BMP-7 added to allograft results in a higherfusion rate than allograft alone or allograft with demineralized bone matrix.

INSTRUMENTED POSTEROLATERAL FUSIONIn the author’s experience, an instrumented posterior/posterolateral fusion is themost commonly performed fusion procedure for the treatment of ASD. Although itis certainly a reflection of one individual’s practice, the author has found that themost common indication to perform surgery for ASD is to proximally extenddecompression and fusion above a previous laminectomy and instrumented fusionin an elderly patient. As discogenic pain is not typical in this subgroup, thepreferred method is posterolateral instrumented fusion in nearly all the cases. Therationale for including instrumentation is to increase the chance for successfulfusion (33). Other, less-frequent indications include primarily facet-mediated orspondylolytic extension pain (i.e., pain worse with extension and minimal withflexion) or multilevel fixation and fusion for an adjacent degenerative scoliosisdeformity.

With this backdrop, several important issues are brought to the foreground.First is the relationship between bone density and pedicle screw purchase in theosteopenic or osteoporotic spine. Cantilever motion from loosened screws can leadto widening and funneling of the inner diameter of the pedicle. When revisingpreviously placed instrumentation, larger diameter screws can be inserted.However, this may not always result in secure fixation. In such cases, the surgeonmay consider alternative methods of improving screw purchase.Polymethylmethacrylate cement can be injected into the vertebral body through

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196 n Bono

the pedicle tract immediately prior to screw placement. Biomechanical studieshave demonstrated this to be an effective means of improving pull-out strength inosteoporotic vertebrae (34).

Another issue is deciding the number of levels that should be included in thefusion. A number of factors are important. Although the degeneration of theadjacent level is usually not contestable, as it is the primary reason for surgery,the integrity of the other discs should be noted. Stopping a fusion just distal to amoderately degenerated segment may result in short-term relief. The follow-upquestion is how long will this positive result last? It is unclear if such moderatelydegenerated levels should be included in the fusion. In the author’s practice, thisdecision is additionally based on the overall alignment of the region and whetheror not a laminectomy is to be performed. If the decompression is to be extendedcranially, fusion is likely to include the marginally degenerated levels. Likewise,instrumentation and fusion is stopped at the first horizontal vertebral level(i.e., endplate parallel to a transverse line drawn along the superior aspect of theiliac crests).

The surgeon may also consider the level at which the proposed fusionconstruct will end. Notwithstanding sagittal or coronal alignment, a long lumbarfusion that ends at L1 will leave only one truly mobile motion segment: T12–L1.The integrity of this segment must be carefully scrutinized. Particularly in ayounger patient who will subject his or her spine to decades of more use, theT12–L1 segment will have a propensity to exhibit an accelerated rate ofdegeneration. Weighed against the disadvantage of having an entirely fusedlumbar spine and thoracolumbar junction, one might consider the addition of T12or even T11 in the revision construct (Fig. 6A and B).

POSTERIOR INTERBODY FUSION (PLIF OR TLIF)Currently, interbody fusion is the procedure of choice for the treatment ofsymptomatic degenerative disc disease, also termed discogenic back pain.Unfortunately, interbody fusion also seems to exhibit the highest rates of ASD.In a recent, unpublished meta-analysis performed by the author and hiscoinvestigators, PLIF resulted in a 47% rate of ASD, while ALIF yielded a 29%and posterolateral fusion a 24% rate of ASD. Postulating that both greater stiffnessof the fusion and a posterior approach are contributing factors, these data suggestthat PLIF or TLIF carry both of these negative characteristics. Fortunately, only asmall minority of patients eventuate the need for subsequent surgery.

Despite its seemingly plagued fate, a PLIF or TLIF is a viable option insome cases of symptomatic discogenic low-back pain secondary to an adjacentdegenerated disc. In the author’s practice, TLIF appears to be more useful thanPLIF. The author’s indication for TLIF for ASD is pain emanating from the discwith or without unilateral radiculopathy from a disc herniation, protrusion, orforaminal stenosis. The need for discography is judged on a case-by-case basis.A wide decompression of the exiting and descending nerve root is an obligatorystep in the operation by nature of removal of the entire facet joint. It isparticularly amenable to the revision situation as the disc space is actuallyapproached lateral to the dural sac, obviating neural retraction for visualization.Relative contraindications for a TLIF are osteoporotic bone, a fixed segmentalkyphotic deformity, or the inability to place pedicle screws at the level ofsurgery.

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COMBINED ANTERIOR AND POSTERIOR FUSIONAs a preface to the proceeding discussion, the author wishes to briefly address theoption of a stand-alone ALIF in the treatment of ASD. By the nature of the clinicalproblem, the motion segment to be fused is a biomechanical transition pointbetween the stiff fused portion and the remaining mobile segments of the lumbarspine. Although the amount of additional stress placed at the adjacent segment canvary, as it is influenced by the length and alignment of the previous fusion, it is

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FIGURE 6Anteroposterior (A) and lateral (B) radiographs of a 58-year-old woman who had

undergone two previous instrumented fusions. The index surgery was performed atL4–L5. Although she did well from that surgery for about five years, she subsequentlydeveloped ASD at L3–L4 and underwent a revision operation with a laminectomy andfusion from L3 to L4. With a moderate response from that procedure, she developedprogressively worse pain. Imaging at the time of presentation to the author demonstrated aflat-back deformity from L3 to L5 (black dashed line) with advanced disc degeneration atL2–L3 (large white arrow). Interestingly, an extension radiograph revealed that her L1–L2segment had also degenerated but was mobile and exhibited developed hyperlordosis.This effectively corrected her sagittal plane imbalance. As a revision posteriorinstrumentation and fusion was planned, the proximal extent of the fusion had to bedecided. As an L1–L2 fusion would have left the patient with a single mobile lumbar motionsegment (T12–L1) and she clearly demonstrated a proclivity toward symptomatic ASD, itwas decided to extend the fusion to the T11 level so as to “prevent” late degeneration ofthe thoracolumbar junction. Abbreviation: ASD, adjacent segment degeneration.

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reasonable to conclude that it is higher than an intact spine. As the use of ALIF in avirgin spine has been surrounded by considerable controversy regarding itsadequacy as a stand-alone fusion technique (35), it is the author’s strong opinionthat a stand-alone ALIF should not be considered a first-line treatment optionfor ASD.

With that established, an ALIF combined with posterior stabilization with orwithout posterior fusion is a useful surgical technique for symptomatic ASD. In theauthor’s practice, this option is considered in cases in which a fixed, acute kyphoticdeformity requiring correction is present at the operative level. The anteriorapproach to the disc space allows a full release of a contracted ALL as well asremoval of anterior osteophytes. A large interbody device can be placed into thedisc space to maintain the correction as well as to effect fusion. Although there arefew absolute contraindications, an important relative contraindication is a previousanterior lumbar approach that can make dissection and exposure difficult.

Posterior instrumentation, usually transpedicular screws, should be stronglyconsidered following an ALIF proximal or distal to a previously fused segment.Because of unfavorable biomechanics and healing potential, it is considered arequisite following an L5–S1 ALIF below a fused segment.

Role of MIS TechniquesALIF can be performed with a variety of less-invasive surgical techniques utilizingendoscopic or mini-open retroperitoneal approaches. An in-depth discussion ofthese techniques is beyond the scope of this chapter. These techniques are probablybest reserved for those cases in which preoperative alignment is neutral or nearlynormal, as kyphosis correction may be difficult to achieve. They should be avoidedif a previous anterior approach has been performed.

Percutaneous pedicle screw insertion has a potential role for stabilization ofan ALIF performed for ASD. The benefits of this MIS approach are greatest if theprevious fusion does not have to be explored, as may be the case if a solidinterbody fusion is confirmed radiographically or by anterior exploration. For thisindication, the incisions are limited to those needed to place the screws. Somesurgeons have become adept at performing intertransverse fusion through smallparamedian incisions using tubular retractors. This may be elected if additionalposterior fusion is planned.

n CONCLUSIONS

The surgical treatment of ASD can be challenging. Perhaps most important isestablishing a reasonable estimation of what appears to be the major pain generatoror symptom source. Careful preoperative planning must focus not only on themethod of fusion intended for the adjacent degenerated level but also on revisitingor revising the previous instrumentation and fusion sites. Although there are few ifany data regarding the optimal surgical approach, various factors can influence thedecision to utilize one technique over another.

n REFERENCES Q1

1. Buttner-Janz K, Schellnack K, Zippel H, et al. Experience and results with the SBCharite lumbar intervertebral endoprosthesis. Z Klin Med 1988; 43:1785–1789.

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2. Cinotti G, David T, Postacchini F. Results of disc prosthesis after a minimum follow-upperiod of 2 years. Spine 1996; 21:995–1000.

3. deKleuver M, Oner FC, Jacobs WCH. Total disc replacement for chronic low back pain:background and a systematic review of the literature. Eur Spine J 2003; 12:108–116.

4. Ghiselli G, Wang JC, Bhatia NN, et al. Adjacement segment degeneration in the lumbarspine. J Bone Joint Surg Am 2004; 86A:1497–1503.

5. Kumar MN, Baklanov A, Chopin D. Correlation between sagittal plane changes andadjacent segment degeneration following lumbar spine fusion. Eur Spine J 2001; 10:314–319.

6. Lee CK. Accelerated degeneration of the segment adjacent to a lumbar fusion. Spine1988; 13:375–377.

7. Sengupta DK. Dynamic stabilization devices in the treatment of low back pain. OrthopClin North Am 2004; 35:43–56.

8. Sengupta DK, Mulholland RC. Fulcrum assisted soft stabilization system: a newconcept in the surgical treatment of degenerative low back pain. Spine 2005; 30:1019–1029.

9. Brantigan JW, Stefee AD, Lewis ML, et al. Lumbar interbody fusion using the BrantiganI/F cage for posterior lumbar interbody fusion and the variable pedicle screwplacement system. Spine 2000; 25:1437–1446.

10. Ghiselli G, Wang JC, Hsu WK, et al. L5–S1 segment survivorship and clinical outcomeanalysis after L4–L5 isolated fusion. Spine 2003; 28:1275–1280.

11. Kanayama M, Hashimoto T, Shigenobu K, et al. Adjacent-segment morbidity after Grafligamentoplasty compared with posterolateral lumbar fusion. J Neurosurg 2001; 95:5–10.

12. Kuslich SD, Ulstrom CL, Grifith SL, et al. The Bagby and Kuslich method of lumbarinterbody fusion. History, techniques, and 2-year follow-up results of a United Statesprospective, multicenter trial. Spine 1998; 23:1267–1278.

13. Miyakoshi N, Abe E, Shimada Y, et al. Anterior decompression with single segmentalspinal interbody fusion for lumbar burst fracture. Spine 1999; 24:67–73.

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15. Park P, Garton HJ, Gala V, et al. Adjacent segment disease after lumbar or lumbosacralfusion; review of the literature. Spine 2004; 29:1938–1944.

16. Aota Y, Kumano K, Hirabayashi S. Postfusion instability at the adjacent segments afterrigid pedicle screw fixation for degenerative lumbar spinal disorders. J Spinal Disord1993; 8:464–473.

17. Chou W, Hsu C, Chang W, et al. Adjacent segment degeneration after lumbar spinalposterolateral fusion with instrumentation in elderly patients. Acta Orthop TraumaSurg Q22002; 122.

18. Etebar S, Cahill DW. Risk factors for adjacent-segment failure following lumbar fixationwith rigid instrumentation for degenerative instability. J Neurosurg 1999; 90:163–169.

19. Hilibrand AS, Robbins M. Adjacent segment degeneration and adjacent segmentdisease: the consequences of spinal fusion? Spine J 2004; 4:190S–194S.

20. Throckmorton TW, Hilibrand AS, Mencio GA, et al. The impact of adjacent level discdegeneration on health status outcomes following lumbar fusion. Spine 2003; 28:2596–2550.

21. Gillet P. The fate of the adjacent motion segments after lumbar fusion. J Spinal DisordTech 2005; 16:338–345.

22. Fujiwara A, Tamai K, Yamato M, et al. The relationship between facet joint osteoarthritisand disc degeneration of the lumbar spine: an MRI study. Eur Spine J 1999; 8:396–401.

23. Wershaupt D, Zanetti M, Boos N, et al. MR imaging and CT in osteoarthritis of thelumbar facet joints. Skeletal Radiol 1999; 28:215–219.

24. Bono CM. Low-back pain in athletes. J Bone Joint Surg Am 2004; 86A:382–396.25. Salerni AA. Minimally invasive removal or revision of lumbar spinal fixation. Spine J

2004; 4:701–705.

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26. Tafazal SI, Sell PJ. Incidental durotomy in lumbar spine surgery: incidence andmanagement. Eur Spine J 2005; 14:287–290.

27. Young S, Veerapen R, O’Laoire SA. Relief of lumbar canal stenosis using multilevelsubarticular fenestrations as an alternative to wide laminectomy: preliminary report.Neurosurgery 1988; 23:628–633.

28. Brodsky AE, Kovalsky EW, Khalil MA. Correlation of radiologic assessment of lumbarspine fusions with surgical explorations. Spine 1991; 16:S261–S265.

29. Hamill CL, Simmons ED. Interobserver variability in grading lumbar fusions. J SpinalDisord 1997; 10:387–390.

30. Larsen JM, Rimoldi RL, Capen DA, et al. Assessment of pseudarthrosis in pedicle screwfusion: a prospective study comparing plain radiographs, flexion/extension radio-graphs, CT scanning, and bone scintigraphy with operative findings. J Spinal Disord1997; 9:117–120.

31. Kant AP, Daum WJ, Dean SM, et al. Evaluation of lumbar spine fusion. Plainradiographs versus direct surgical exploration and observation. Spine 1995; 20:2313–2317.

32. Vaccaro AR, Patel T, Fischgrund JS, et al. A 2-year follow-up pilot study evaluating thesafety and efficacy of op-1 putty (rhbmp-7) as an adjunct to iliac crest autograft inposterolateral lumbar fusions. Eur Spine J 2005; 14:632–639.

33. Bono CM, Lee CK. Critical analysis of trends in fusion for degenerative disc diseaseover the past 20 years: influence of techniques on fusion rate and clinical outcome.Spine 2004; 29:455–463.

34. Cook SD, Salkeld SL, Stanley T, et al. Spine J 4 Q3; 4:402–408.35. Beutler WJ, Peppelman WC. Anterior lumbar fusion with paired BAK standard and

paired BAK Proximity cages: subsidence incidence, subsidence factors, and clinicaloutcome. Spine J 2003; 3:289–293.

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Posterior Fixation Techniques forAtlantoaxial Instability

14 Yoichi Shimada, Kazuhiro HasegawaSatoshi Asano, and Naohisa Miyakoshi

n INTRODUCTION

Atlantoaxial instability can be caused by trauma, inflammatory diseases such asrheumatoid arthritis, congenital malformation, or malignancy. Clinically orradiographically significant atlantoaxial subluxation is best treated by reductionand stabilization of the C1–C2 joint. Currently, this has been best accomplishedthrough reduction and fusion of the atlantoaxial complex with several forms ofinternal fixation, usually through a posterior approach.

Since the first report of posterior atlantoaxial fusion for the treatment ofatlantoaxial instability by Gallie in 1939 (1), various posterior wiring techniques foratlantoaxial instability have been developed to provide fixation of C1–C2segments, including Brooks fusion, modified Gallie techniques, and the Halifaxinterlaminar clamp (1–5). Since 1987, when Magerl and Seemann introduced thetechnique of transarticular screw placement, it has become the standard procedurefor posterior fusion of C1–C2 (6). Also, other methods such as posterior intra-articular screw fixation (7) and posterior screw-rod fixation (8) have been reportedfor the treatment of atlantoaxial lesion. In this chapter, the authors summarizevarious techniques of posterior atlantoaxial fixation and review clinical andradiological records of their patient series who have undergone posterioratlantoaxial fixation.

n McGRAW’S POSTERIOR WIRING

BACKGROUNDClassic instrumentation for the atlantoaxial instability with posterior wiring hasbeen used for many years in the form of the Brooks or Gallie fusion (1–3). Beforethe introduction of transarticular screw fixation, posterior wiring was consideredthe gold standard for treating atlantoaxial instability. There are numerous reportsin the literature detailing successful clinical outcomes using posterior wiringmethods (2,3,9,10). However, several biomechanical studies have shown that thisform of instrumentation does a poor job in resisting rotational and lateral bendingforces (11,12). This is likely the reason for the high nonunion rate for this technique

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Yoichi Shimada Department of Orthopedic Surgery, Akita University School of Medicine, Akita,Japan; Kazuhiro Hasegawa Niigata Spine Surgery Center, Niigata, Japan; Satoshi Asano SaitamaSpine and Spinal Cord Center, Saitama, Japan; Naohisa Miyakoshi Department of OrthopedicSurgery, Akita University School of Medicine, Akita, Japan.

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compared to transarticular screw fixation, despite postoperative Halo vestimmobilization (13–15). In 1973, McGraw and Rusch modified the original Galliewiring techniques (4). Between 1979 and 1992, the authors’ institution had adoptedMcGraw’s technique for the treatment of atlantoaxial instability.

SURGICAL PROCEDUREFor two or three weeks prior to the procedure, the head is held in traction usingCrutchfield’s device or Halo traction to reduce the dislocation of C1–C2. Thepatient is placed in the spine frame in the prone position, while the head and neckare maintained in the extended position with traction. A rectangular cortico-cancellous graft, measuring approximately 3 cm in length, is cut from the posterioriliac crest. Notches are fashioned in the graft to accommodate the spinous processof the C2. A graft is placed between the curettaged laminae of the atlas and axis,and fixed with a stainless steel wire (0.97mm in diameter) passing around the archof the atlas and beneath the spinous process of the axis (Fig. 1). Postoperatively, thepatient is held in a Halo vest for approximately one month, followed by applicationof a sternal occipital mandibular immobilization (SOMI) or Philadelphia cervicalorthosis for three months. A representative case that underwent McGraw’sposterior wiring is presented in Figure 2.

51525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100 FIGURE 1

McGraw’s posterior wiring technique.

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SURGICAL RESULTS (16)Nineteen consecutive patients (10 males, 9 females) with a mean age of42.5 years (range, 10–74 years) were treated with McGraw’s wiring technique.The cause of atlantoaxial instability included rheumatoid arthritis (nine patients),os odontoideum (six patients), posttraumatic causes (two patients), and othercauses (two patients). Seventeen (89%) of the 19 patients had complained of neckpain as the main symptom. Neurologic abnormalities were found in sevenpatients (37%).

No cases of severe complications such as vertebral artery injury, iatrogenicneurological deficit, or deep wound infection were observed. Clinical outcomes,assessed according to relief of pain, were rated as excellent in ten patients (53%),good in five patients (26%), fair in three patients (16%), and poor in one patient(5%). The average follow-up period was 12.2 years (range, 2–22 years). Sixteenpatients (84%) achieved solid osseous fusion and three patients developedpseudoarthrosis. The fusion rate of the McGraw or modified Gallie procedurehas been previously reported to be 50% to 96% (10,17–19), which is comparable tothe fusion rate of the authors’ series (84%).

n BROOKS’ SUBLAMINAR WIRING

SURGICAL PROCEDUREThe patient is placed in the spine frame in the prone position, while the head andneck are maintained in the extended position with traction. Two rectangularcortico-cancellous grafts are cut from the posterior iliac crest. Notches arefashioned in the graft to accommodate between the C1 posterior arch and C2lamina. Two grafts are placed between the curettaged laminae of the atlas and axis,

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FIGURE 2A 53-year-old female with rheumatoid arthritis. (A) Lateral flexion radiograph

showing a subluxation at C1–C2. (B) Lateral radiographs obtained postoperatively and (C)13 years after McGraw posterior wiring, demonstrating solid fusion.

Posterior Fixation Techniques for Atlantoaxial Instability n 205

and fixed with a stainless steel wire (0.97mm in diameter) passing beneath the archof the atlas and the axis (Fig. 3).

A representative case that underwent Brooks’ sublaminar wiring is presentedin Figure 4.

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FIGURE 3Brooks’ sublaminar wiring.

FIGURE 4A 20-year-old female with rheumatoid arthritis. (A) Lateral flexion radiograph

showing a subluxation at C1–C2. (B) Lateral extension radiographs showing a reduction atC1–C2 and (C) 13 years after McGraw posterior wiring, demonstrating solid fusion.

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n TRANSARTICULAR SCREW FIXATION

BACKGROUNDTransarticular screw fixation of the atlantoaxial joints (6), with posterior bonegrafting, offers immediate true three-point stability without major complicationwhen performed properly (20). The reliable stability in translational and rotationaldisplacement results in a high fusion rate and abridges external support (soft collaris sufficient) for postoperative management. However, the potential risk of injuryto the vertebral artery is a disadvantage (Fig. 5). The high stability rates afforded bythis technique do appear to justify the inherent risks of this procedure even in casesinvolving bone fragility such as rheumatoid arthritis patients (21).

The risk of vertebral artery was, however, 4.1% per patient or 2.2% per screwinserted, including both known and suspected cases. The risk of neurologicaldeficit from vertebral artery injury was 0.2% per patient or 0.1% per screw, and themortality rate was 0.1% (22). Therefore, the potential risk of this procedure shouldbe clearly explained to the patient before surgery even though the technique isexcellent.

INDICATIONSAlthough any atlantoaxial instability from various etiologies can be a surgicalindication for transarticular screw fixation, good indications of the transarticular

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FIGURE 5A sagittal CT reconstruction of a case with high-riding vertebral artery. This

section was obtained 3mm lateral to the left lateral edge of the spinal canal. Asterisk,vertebral artery groove; dotted arrow, course of transarticular screw.


fixation are patients with reducible atlantoaxial instabilities, normal anatomy ofaxis and atlas, and the following:

1. nontraumatic instability of the atlantoaxial segment (rheumatoid arthritis,Down’s syndrome, cerebral palsy, etc.) and

2. traumatic instability including fractures of the atlas, axis, and ligamentousinjuries.

CONTRAINDICATIONSContraindications for the procedure are irreducible atlantoaxial instabilities, andanomalies of axis or atlas (congenital malformations, missing pedicle) andvertebral artery. In these patients, there is a high risk of vertebral artery injury ormalposition of the screw.

SURGICAL PROCEDURE

Positioning and DrapingThe patient is placed in the prone position with the head separately fixed withMayfield skull device, allowing unconstrained positioning.

Positioning of the cervical spine is crucial for correctly inserting the screws.Then using the lateral image of c-arm, the position is manipulated to reduce theC1–C2 relationship to as normal as possible. Final anatomical reduction isperformed just prior to screw insertion by pushing the tip of C2 spinous process Q1.Bilateral shoulders are pulled down caudally using nonelastic tape to confirmwhole cervical alignment in c-arm image. Then, the occipitocervical area and theposterior iliac crest for graft harvesting are draped. C-arm is placed followingdraping.

ExposureThe skin incision is made in the midline from the occiput to the midcervical level.The nuchal fascial and the superficial muscles are divided. The C2 spinous processis identified as a landmark. The insertions of rectus major and minor, obliquecapitis inferior, and semispinalis cervicis to the C2 spinous process are detachedwith marking by sutures, so that the muscles are able to be repaired prior to skinclosure. Exposure is extended from the posterior edge of the occiput, atlas, to theC2–C3 facets, and sufficiently lateral to each facet. Soft tissues are removed,exposing interlaminar spaces. Subperiosteal dissection reveals the medial border ofC2 isthmus and, if necessary, the atlantoaxial joint by retracting C2 nerve rootcranially (Fig. 6).

Screw InsertionThe authors use a cannulated screwing system. The system consists of threadedKirschner wires, self-tapped cannulated screws, and tubes for percutaneousapplication (Fig. 7). Stab incisions of 5mm are separately made 2 cm lateral to themidline at the C7 spinous process for insertion of a tube (Fig. 8). The insertion pointfor the guide wire is determined under c-arm image control. The point is usuallythe caudal part of the facet. The insertion point is drilled using a φ3mm steel barand the guide wire is carefully inserted toward the upper half of the anteriortubercle of the atlas while maintaining anatomic reduction by pushing the tip of

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208 n Shimada

the C2 spinous process toward C1 (Fig. 9A). The direction of the guide wire isstrictly sagittal and 2 to 3mm lateral to the medical border of the isthmus so thatthe wire does not violate the vertebral artery or the spinal canal. The guide wireinsertion should be performed manually so as to feel the resistance of the tipof the wire, especially across the atlantoaxial joint and avoid a sudden deviation ofthe wire (Fig. 9B). Once the guide wire is inserted, the reduced position can bemaintained without pushing the C2 spinous process. A self-tapped cannulatedscrew is inserted following the guide wire (Fig. 10A). The other side of a screw isinserted in the same way (Fig. 10).

Bone GraftA posterior bone graft is indispensable to obtaining a permanent fusion. A stronganchor for the bone graft is, however, not required, because atlantoaxial stabilityhas already been secured by bilateral transarticular screw fixation. We use theclassical bone graft methods by Gallie (1) and Brooks (3), or a modification of theseprocedures (Fig. 11). These procedures have been described earlier in this chapter.

POSTOPERATIVE CAREAfter confirmation of awakening, normal ventilation, and oxygenation, extubationis performed. Respiratory condition and vital signs are strictly monitored for24 hours after surgery. Sitting Q2and walking with a soft collar is permitted on thefirst postoperative day. The collar should be worn by the patient for eight weekswhen not in bed. The patient can be discharged when the wound is healed andX-ray examination is satisfactory.

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C2 spinousprocess

C2 lower facet

Dural tube

Occiput

C3

FIGURE 6Exposure.


Rehabilitation of the neck or initiation of sports activities are allowed eightweeks after surgery. Clinical and X-ray examinations are scheduled 2, 6, 12, and24 months after surgery.

PITFALLS AND COMPLICATIONS

1. If the screw is unfortunately inserted in the wrong position, one should switchto a conventional fixation technique, Brook’s, or triple-wiring method (23), etc.,without screw technique to avoid serious complications. In this case, post-operative external support should be sufficient, Halo vest, etc.

2. Injury to the vertebral artery during screwing through the isthmus of C2 ispossible. If massive arterial bleeding happens when removing the guide wire,damage of the vertebral artery should be strongly suspected. The drilling holeshould be plugged with bone wax. In this case, atlantoaxial screwing to the

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Outer tube

Inner tube

Guide wire(Kirschner)

Cannulatedscrew

(A)

(B)

FIGURE 7A cannulated screwing system.

210 n Shimada

contralateral side is prohibited, because bilateral violation of the vertebral arterycan be fatal.

3. A dural tear can occur, although rarely; in this case, the damaged site should beidentified and directly sutured.

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FIGURE 8A schema of application of a cannulated tube through a stab incision for guiding

a threaded Kirschner wire and screw.

FIGURE 9Guide (Kirschner) wire insertion.


SURGICAL RESULTSSeventeen patients (4 males, 13 females) with a mean age of 56 years (range10–75 years) were treated with Magerl transarticular screw fixation between 1992and 2000. The causes of atlantoaxial instability were rheumatoid arthritis in ninepatients, os odontoideum in two, posttrauma in five, and unknown in one.

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FIGURE 10Screwing through a guide wire.

FIGURE 11Bone graft. (A) C1–C2 sublaminar wiring using polyethylene cables. (B) Modified

Brooks’ method. A trimmed iliac bone is secured by bilateral C1–C2 sublaminal cables.

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Fourteen (82%) of the 17 patients had complained of neck pain as the mainsymptom. Neurologic abnormality was found in nine patients (53%). The averagefollow-up period was seven years (range, 2–9 years).

Clinical outcome, assessed according to relief of pain, was excellent or goodin 82% of the patients. Sixteen patients (94%) demonstrated complete fusion. Onlya 70-year-old male had an ankylosing spine associated with rheumatoid arthritisthat resulted in pseudoarthrosis. No cases of vertebral artery injury, iatrogenicneurological deficit, infection, or instrumentation failure were observed.Complications related to the Magerl procedure included one case of screwpenetration of the mucous membrane of the pharynx. A representative case thatunderwent transarticular screw fixation is presented in Figures 12 and 13.

n INTRA-ARTICULAR SCREW FIXATION

BACKGROUNDIn 1996, Tokuhashi et al. (7) developed a new screw fixation technique foratlantoaxial posterior stabilization, in which the screw is inserted into theatlantoaxial joint along the articular surface under direct view without radio-graphic control (Fig. 14). This screw fixation device was used in combination with aposterior fixation device such as the Halifax interlaminar clamp (OSTEONICS,Allendale, NJ). Tokuhashi et al. (7) reported the first clinical outcomes in 11 patientswith atlantoaxial instability who had been treated with intra-articular screwfixation in combination with a Halifax interlaminar clamp. In their series, occipitaland neck pain and neural deficit improved. In addition, bony fusion with nocorrection loss was shown on radiography, without any patients experiencingvascular or neural complications (7). Since 2002, the authors’ institution hasadopted this procedure for the treatment of atlantoaxial lesions.

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FIGURE 12A 62-year-old woman with atlantoaxial instability due to rheumatoid arthritis. (A)

T2-weighted sagittal image. (B) Flexion X ray. (C) Extension X ray.


SURGICAL PROCEDURE (7)In this procedure, the patient is placed in the prone position while maintainingC1–C2 reduction as much as possible; the reduction is confirmed with c-armfluoroscopy or radiography. A midline exposure of C1 and C2 posterior elements isthen achieved. Careful dissection with a small dissector is performed along thesuperior laminar ridge of C2 until the atlantoaxial joints are exposed (Fig. 15A).When the dissector reaches the atlantoaxial joints, the surgeon can detect a lightsensation of penetration of the capsule because of the loss of resistance. Thecapsule usually can be dissected freely with a small dissector and retractedcranially together with the C2 nerve root. Venous bleeding, if encountered, can be

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FIGURE 13Two years after transaxial atlantoaxial fixation: (A) Anteroposterior open mouth

view. (B) Lateral neutral position X ray.

FIGURE 14Intra-articular screw fixation technique.

214 n Shimada

controlled by packing with Avitene (Davol Inc., Woburn, MA). After exposing thejoint surfaces, a 1mm Kirschner wire is inserted into the atlantoaxial joints as aguide for screw insertion (Fig. 15B).

A titanium intra-articular screw (5.0–6.5mm in diameter, 8.0–10.0mm inlength; KISCO-DIR Co. Ltd., Osaka, Japan) is inserted after interlaminar clampfixation and hemicortical bone grafting from the posterior iliac crest (Fig. 15C).After the reduced position is confirmed by radiography, fine adjustment of theclamp is performed, the position of the atlantoaxial joints is checked, and tappingand screw insertion are performed using a Kirschner wire as a guide (Fig. 15Dand E). The intra-articular screws are buried in the atlantoaxial joints, with caretaken to avoid the greater occipital nerves located medially and runningsuperficially to the C1–C2 articulation (Fig. 15F). As the final step, the clamp istightened again to place cephalocaudal pressure on the intra-articular screws. Thepatients are allowed to sit and walk with a Philadelphia orthosis three days aftersurgery. The orthosis is applied for three months.

Because this screw can be inserted under direct view without radiographiccontrol, it potentially decreases the risk of damage to the spinal cord, dura matter,and vertebral artery (7). To counter the risk of massive bleeding from theperiarticular venous plexus during exposure of the atlantoaxial joints, it isimportant to expose only the joint surface and retract the capsule of the atlantoaxialjoints cranially with the C2 nerve root and the periarticular venous plexus (7).A representative case that underwent intra-articular screw fixation with posteriorbone grafting is presented in Figure 16.

SURGICAL RESULTSSeven patients (three males, four females) with a mean age of 60.5 years (range,38–79 years) have been treated with intra-articular screw fixation with bonegrafting since 2002. The causes of atlantoaxial instability were rheumatoid arthritisin one patient, posttrauma in five, and unknown in one.

Clinical outcome, assessed according to relief of pain, was excellent or goodin 96% of the patients. All patients (100%) demonstrated complete fusion. Duringand after surgery, no cases of vertebral artery injury, iatrogenic neurological deficit,infection, or instrumentation failure were observed. No complications wereencountered when the intra-articular screw fixation was used.

n C1 LATERAL MASS SCREWS, C2 PEDICLE SCREWS, ANDROD FIXATION

BACKGROUNDHarms and Melcher (8) reported a new technique for individual screw placementin C1 lateral mass and C2 pedicle that minimizes the risk of injury to the vertebralartery and allows intraoperative reduction and fixation of the atlantoaxial complexwithout the need for placing any instrumentation under the posterior arch of C1.

SURGICAL PROCEDURE (8)The cervical spine is exposed subperiosteally from the occiput to C2. Q3The C1–C2complex exposed to the lateral border of the C1–C2 articulation. The C1–C2 joint is

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FIGURE 15Surgical procedure for intra-articular screw placement for atlantoaxial instability

(7): (A) Exposure of posterior atlantoaxial joints. (B) Insertion of a 1mm Kirschner wire intothe atlantoaxial joints as a guide for screw insertion. (C) Interlaminar clamp fixation in thereduced position of atlantoaxial joints and hemicortical bone grafting. (D) Tapping using aKirschner wire as a guide. (E) Intra-articular screw insertion using a Kirschner wire as aguide. (F) Buried intra-articular screws in the atlantoaxial joints. Source: From Ref. 7.

216 n Shimada

exposed and opened by dissection over the superior surface of the C2 parsinterarticularis (Fig. 17). This joint is a key anatomic landmark for accurateplacement of the C1 lateral mass screw. The C2 nerve root is retracted in a caudaldirection to expose the entry point for the C1 screw, which is in the middle of thejunction of the C1 posterior arch and the midpoint of the junction of the C1posterior arch and the midpoint of the posterior inferior part of the C1 lateral mass.This entry point is marked with 2mm high-speed burr to prevent slippage of the

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C

C2

Venous plexious

Dura

FIGURE 17Exposure for C1 lateral mass screws and C2 pedicle screws.

FIGURE 16A 57-year-old male with posttraumatic atlantoaxial instability underwent intra-

articular screw fixation with posterior bone grafting. (A) Preoperative lateral flexionradiograph showing subluxation at C1-C2. (B,C) Lateral and anteroposterior radiographsobtained one year after surgery demonstrating good positioning of the intra-articularscrews (buried in the atlantoaxial joints) and solid fusion.


drill point. After drilling the hole is tapped, and a 3.5mm polyaxial screw ofappropriate length is inserted bicortically into the lateral mass of C1. Hong et al.(24) reported that the width and height of the atlas lateral mass were larger thanthose of the C2 pedicle, and there was enough space to insert a 3.5mm diameterscrew in the atlas lateral mass over the C2 nerve root. The direction of the screwshould be about 20˚ anterosuperior in the vertical plane and 15˚ inward in thehorizontal plane. The suitable length of the screw should be approximately 22mminside the lateral mass (24). We recently introduced the C1 screw insertion from theC1 posterior arch to the C1 lateral mass. The entry point is 17mm lateral from thecenter of the C1 posterior arch (Fig. 18). The direction of the screw was 10˚ inwardin the horizontal plane. The entry point of a C2 pedicle screw is in the cranial andmedial quadrant of the isthmus surface of C2. The pilot hole is prepared with a2mm drill bit. The direction of the bit is approximately 20˚ to 30˚ in a convergentand cephalad direction, guided directly by the superior and medial surface of theC2 isthmus (Fig. 19). The hole is tapped, and a 3.5mm polyaxial screw of theappropriate length is inserted bicortically.

A representative case that underwent C1 lateral mass screws, C2 pediclescrews, and rod fixation is presented in Figures 20 to 22.

n CONCLUSIONS

Various posterior stabilization techniques with wiring, including McGraw’stechnique, have been developed to manage atlantoaxial instability. Ever sinceMagerl and Seemann developed the transarticular screw fixation technique, ithas been the standard procedure for posterior atlantoaxial fixation. However,the technique is technically demanding and poses a risk of injury to the nerves

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FIGURE 18Insertion points into C1 lateral mass and C2 pedicle.

218 n Shimada

and vertebral arteries. Alternatively, the intra-articular screw fixation technique,in which the screw is inserted into the atlantoaxial joint along the articularsurface under direct view without radiographic control, is a safe and effectiveprocedure for the treatment of atlantoaxial lesion. The C1 lateral mass screws,

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C1 lateral mass screw

C2 pedicle screw

C1 posterior arch

C2 lamia

Dura

FIGURE 19After insertion of C1 lateral mass screws and C2 pedicle screws.

FIGURE 20A 66-year-old male with os odontoideum. (A) Lateral radiograph showing a

subluxation at C1–C2. (B) Lateral T2-WI MRI showing a spinal cord atrophy and a highintensity in the spinal cord.


C2 pedicle screws, and rod fixation minimizes the risk of injury to the vertebralartery and allows intraoperative reduction and fixation of the atlantoaxialcomplex without the need for placing any instrumentation under the posteriorarch of C1.

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FIGURE 22CT scan after fixation with C1 lateral mass, C2 pedicle, and rod fixation. (A) C1

lateral mass screws. (B) C2 pedicle screws.

FIGURE 21X ray after fixation with C1 lateral mass, C2 pedicle, and rod fixation.

220 n Shimada

n REFERENCES

1. GallieWE. Fractures anddislocations of the cervical spine. Am J Surg 1939; 46(3):495–499.2. Anderson LD, D’Alonzo RT. Fractures of the odontoid process of the axis. J Bone Joint

Surg Am 1974; 56(8):1663–1674.3. Brooks AL, Jenkins EB. Atlantoaxial arthrodesis by the wedge compression method.

J Bone Joint Surg Am 1978; 60(3):279–284.4. McGraw RW, Rusch RM. Atlantoaxial arthrodesis. J Bone Joint Surg Br 1973; 55(3):

482–489.5. Moskovich R, Crockard HA. Atlantoaxial arthrodesis using interlaminar clamps. An

improved technique. Spine 1992; 17(3):261–267.6. Magerl F, Seemann PS. Stable posterior fusion of the atlas and axis by transarticular

screw fixation. In: Kehr P, Weidner A, eds. Cervical Spine I. Wien: Springer-Verlag, 1987,pp. 322–327.

7. Tokuhashi Y, Matsuzaki H, Shirasaki Y, et al. C1–C2 intra-articular screw fixation foratlantoaxial posterior stabilization. Spine 2000; 25(3):337–341.

8. Harms J, Melcher RP. Posterior C1–C2 fusion with polyaxial screw and rod fixation.Spine 2001; 26(22):2467–2471.

9. Coyne TJ, Fehlings MG, Wallace MC, et al. C1–C2 posterior cervical fusion: long-termevaluation of results and efficacy. Neurosurgery 1995; 37(4):688–693.

10. Ranawat CS, O’Leary P, Pellicci P, et al. Cervical spine fusion in rheumatoid arthritis.J Bone Joint Surg Am 1979; 61(7):1003–1010.

11. Grob D, Crisco JJ, Panjabi MM, et al. Biomechanical evaluation of four differentposterior atlantoaxial fixation techniques. Spine 1992; 17(5):480–490.

12. Henriques T, Cunningham BW, Olerud C, et al. Biomechanical comparison of fivedifferent atlantoaxial posterior fixation techniques. Spine 2000; 25(22):2877–2883.

13. Farey ID, Nadkarni S, Smith N. Modified Gallie technique versus transarticular screwfixation in C1–C2 fusion. Clin Orthop Relat Res 1999; 359:126–135.

14. Jeanneret B, Magerl F. Primary posterior fusion C1/2 in odontoid fractures: indications,technique, and results of transarticular screw fixation. J Spinal Disord 1992; 5(4):464–475.

15. Govender S, NgCelwane MV. Post-traumatic ligamentous instability of the atlantoaxialjoint: a comparison between the Gallie and Brooks fusions. Injury 1993; 24(2):126–128.

16. Hongo M, Shimada Y, Miyakoshi N, et al. Posterior fixation for atlantoaxial instability:a comparison between McGraw’s method and Magerl’s transarticular screw fixation.22nd World Congress of SICOT/SIROT, August 23–30, 2002, San Diego. Abstract book,p. 505.

17. Ferlic DC, Clayton ML, Leidholt JD, et al. Surgical treatment of the symptomaticunstable cervical spine in rheumatoid arthritis. J Bone Joint Surg Am 1975; 57(3):349–354.

18. Larsson SE, Toolanen G. Posterior fusion for atlantoaxial subluxation in rheumatoidarthritis. Spine 1986; 11(6):525–530.

19. Thompson RC Jr, Meyer TJ. Posterior surgical stabilization for atlantoaxial subluxationin rheumatoid arthritis. Spine 1985; 10(7):597–601.

20. Grob D, Jeanneret B, Aebi M, et al. Atlantoaxial fusion with transarticular screwfixation. J Bone Joint Surg Br 1991; 73(6):972–976.

21. Casey AT, Madawi AA, Veres R, Crockard HA. Is the technique of posteriortransarticular screw fixation suitable for rheumatoid atlantoaxial subluxation? Br JNeurosurg 1997; 11:508–519.

22. Wright NM, Lauryssen C. Vertebral artery injury in C1-2 transarticular screw fixation:results of a survey of the AANS/CNS section on disorders of the spine and peripheralnerves. American Association of Neurological Surgeons/Congress of NeurologicalSurgeons. J Neurosurg 1998; 88(4):634–640.

23. McAfee PC, Bohlman HH, Wilson WL. Triple wire fixation technique for stabilization ofacute fracture, dislocations of the cervical spine: a biomechanical analysis. Orthop Trans1985; 9:142.

24. Hong X, Dong Y, Yubing C, et al. Posterior screw placement on the lateral mass of atlas:an anatomic study. Spine 2004; 29:500–503.

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Long-Term Implications of MinimallyInvasive Lumbar Spinal Fusion

15 Kai-Uwe Lewandrowski

n INTRODUCTION

Minimally invasive spinal (MIS) fusion techniques have become commonplace inlumbar spinal fusion surgery. Similar trends are occurring in areas involving thecervical and thoracic spine (1–6). There is no question that these techniques havewell-accepted benefits, with improved clinical outcome data in the short term(7–9). For example, blood loss, use of narcotics following surgery, length of hospitalstay, and overall utilization of in-patient hospital resources are significantlyreduced (9). Moreover, postoperative rehabilitation potential, patient functioning,and return-to-work data compare favorably with clinical outcomes obtained withopen lumbar fusions. However, it is unclear whether there are any advantages inthe long term (10). In fact, it has been argued that reduction in visual analog painscores and Oswestry disability scores in patients who underwent open versusminimally invasive lumbar fusion are similar after six months postoperatively (10).This is similar to initial outcomes in lumbar total disc arthroplasty (TDA), wherethe benefits of early return to function have had no impact on the overall clinicalimprovement later on (11).

However, there are other controversial issues surrounding the introduction ofminimally invasive techniques into lumbar spinal fusion surgery, some of whichare increasingly recognized. For instance, the need for posterolateral fusion alongwith MIS interbody fusion has been questioned, and there are some surgeons whodo not routinely perform it (12,13). If it is performed, the question then becomeswhat type of bone graft should be used, and if autologous bone graft harvest isperformed, how much morbidity it adds to the MIS procedure that couldpotentially dilute its potential benefits (14). In addition, the quality of thedecortication and preparation of the posterolateral gutter for fusion procedure hasbeen questioned. Therefore, some surgeons rely on the interbody fusion.

The interbody fusion can be challenging through a minimal access portalsuch as a 22 mm Q1Metrx± tube; specifically when it is done at the L5-S1 level. Ofparticular concern is the inability to assess the placement of interbody fusion cagesunder direct visualization and to assess the consequences of appropriaterestoration of saggital alignment.

Another problem that is increasingly recognized relates to myofascial painsyndromes from pedicle screws and screw-rod constructs that had been placedpercutaneously under fluoroscopic guidance rather than direct visualization. The

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Kai-Uwe Lewandrowski Department of Orthopaedics, University Medical Center, Center forAdvanced Spinal Surgery of Southern Arizona, Tucson, Arizona, U.S.A.

223

problem here is twofold. First, open lumbar exposures allow appropriate recessingof pedicle screws by preparing the pedicle entry sites. Excess bony overhang fromhypertrophic facet joints can be removed without violating the integrity of the jointitself. Second, open exposures are more likely to result in more scarring of theparaspinal muscles, thus insulating metallic implants from the surroundingnormal tissues. It has been speculated that the lack of excess scar formation in MISexposures is one of the contributing factors to myofascial pain syndromes thatresult in higher rates of postfusion implant retrieval surgeries.

In other words, the analysis of clinical outcomes with MIS versus openlumbar surgeries is not only a matter of simple comparison. Although the goals ofopen and MIS lumbar fusion surgery are very similar (relief of pain, decompres-sion of neural elements, and restoration of spinal stability), and the surgeriesthemselves appear seemingly similar (same surgery through smaller incision), it isbecoming evident upon closer examination that they are in fact different surgeries,with their own specific technique-related problems.

The problem of comparing long-term clinical outcomes with lumbar spinalfusions using either the open or the MIS approach is further complicated by thefact that most clinical outcome studies on lumbar spinal fusion end at two-years offollow-up, thus making an objective assessment nearly impossible (15). Very fewlumbar fusion patient cohorts have been followed to 10 years or longer. In thischapter, long-term implications of MIS lumbar fusion techniques are discussed.This is by no means an all-encompassing analysis but merely a description of someof the problems that have been described in the literature along with clinicalillustrations from the author’s own clinical series.

n MIS INTERBODY FUSION TECHNIQUES

It is commonly recognized that the goals of spinal fusion surgery are the samewhether it is carried out through the MIS approach or through a traditional midlineopen incision. The biological challenges are the same: fusion bed preparation,decortication, harvest and preparation of bone grafts and bone graft extenders, andinstrumentation and assembly of spinal fusion constructs.

There are some differences between minimally invasive and open fusiontechniques that may have some influence on long-term outcomes. Visualization islimited through small mini-open or true percutaneous incisions. Therefore,discectomy and endplate preparation may be limited and the fusion outcomemay be affected. Another issue is the role of autologous bone graft harvest. Mostsurgeons performing MIS fusion surgery will not take autologous iliac crest graftsince it adds to the morbidity of the procedure. Instead, they use local bone graftharvested during the decompression and/or bone graft extenders, and morerecently, recombinant bone morphogenetic protein 2 (rh-BMP-2), now commer-cially available as Infuse± (7–10). To date, there has been no systematic review ofthe role of autologous versus local bone graft materials with or without the use ofrh-BMP-2 in interbody fusions carried out using the minimally invasive technique.

Most of the bone graft substitutes and extenders, if they have been studied atall, have been evaluated in a posterolateral fusion rabbit model in comparison toautologous or local bone graft. Their osteoinductive and osteoconductive potentialhas been evaluated in the posterolateral fusion gutter (16–19). However, littleinformation is available as to what their performance is in the interbody fusion

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224 n Lewandrowski

space. Although there are some new demineralized bone matrix products, such asthe Expanse± (Osteotech, NJ), that have been specifically designed for interbodyfusion, long-term data on their performance in comparison to iliac crest bone graftis still unavailable.

Over the last several years, the use of rh-BMP-2 has found wide application forinterbody fusions. It is assumed that it supersedes the use of iliac crest autograft boneas it induces the body to grow its own bone (20–23). In 2000, the Food and DrugAdministration (FDA) approved the use of rh-BMP-2 for anterior interbody fusionwhenused inconjunctionwith theLumbarTaperedFusionDevice,LTcage± (SofamorDanek) (5). Since then, clinical studieshave indicatedequivalent interbody fusion ratesbetween rh-BMP-2 and iliac crest bone graft (23,24). Good clinical results have alsobeendemonstratedwith“off-label” applications inposterior interbody lumbar fusions(25). The small and medium Infuse± kits come with a 4.9mg vial of rh-BMP-2.According to themanufacturer, only 4.2mg of the 4.9mg of rh-BMP-2 is applied to the

Q2absorbable collagen sponges following reconstitution.However, there is someconcernabout that dosage being too high, as it was found to be associated with bone loss andvertebral osteolysis in some cases. When comparing the technique of posteriorinterbody fusion in a posterior lumbar interbody fusion (PLIF) or transforaminallumbar interbody fusion (TLIF) to the FDA study using LTcages in conjunction withrh-BMP-2, it is evident that the LTcage placement is carried out via endplate-sparingtechniques (26). Thismaynot be the casewith theposterior interbody fusion techniquewhere activebleeding cancellous bonemaybe exposed andwhich seems to change thebalance between osteoclastic resorption and new bone formation. Excessive boneresorption has been reported with the use of rh-BMP-2 in posterior interbody fusion.That clearly has an impact on long-term clinical results, as it is associated with loss ofsaggital correctionand lossof interspaceheightdue to settlingof thecage.At thispoint,it isnot clearwhat thepotential interactionsbetween rh-BMP-2anddifferentbonegraftmaterials and bone graft substitutes are.

n ROLE OF POSTEROLATERAL FUSION

The role of posterolateral fusion is a controversial issue in MIS lumbar fusionsurgery (27–29). If it is performed, there are some technical considerations that mayhave an effect on the long-term outcomes. The visualization in the posterolateralgutter can be limited, particularly if smaller retractor systems are used that offerlimited exposure. That may limit the surgeon’s ability to perform an adequatedecortication between the transverse processes and to deliver an adequate amountof bone graft into the fusion bed. Often, resorption of the bone graft in theposterolateral gutter can be observed, which raises the question of its merit.Recently, larger doses of rh-BMP-2 have been suggested for posterolateral fusion(30). However, it remains to be seen what the role of that procedure is whenperformed in conjunction with interbody fusion.

n RESTORATION OF SAGGITAL AND CORONAL BALANCE

Mobilization of lumbar motion segments may be difficult in some cases. This maybe of particular importance when the interspace is significantly collapsed. Unlikein an open PLIF procedure, where a wide laminectomy with and without removalof the facet joints may be performed, in an MIS exposure, access through the

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Long-Term Implications of Minimally Invasive Lumbar Spinal Fusion n 225

intervertebral disc may only be attempted through a unilateral exposure byremoving the facet joint in its entirety and exposing Kambin’s triangle. Thisapproach is often used in the setting of unilateral leg pain where exposure of thecontralateral lateral recess appears unnecessary. However, it may limit thesurgeon’s ability to perform an adequate discectomy and endplate preparation,and more importantly, to mobilize the interspace by releasing it anteriorly. Only bydoing that will the surgeon be able to place the cage in the desired anterior andmiddle position, and restore adequate lumbar lordosis at the same time.Sometimes though, this is very difficult, and the cage placement may increaseinterspace height but force it into a kyphotic position. It is now well recognizedthat even local kyphosis can potentiate thoracolumbar kyphosis, which is poorlytolerated by the patient (31–33). In addition, there may be problems with correctingcoronal malalignment, which is usually better tolerated than saggital malalign-ment. The latter condition can produce an iatrogenic flat back, which can worsenclinical outcomes significantly. When performing an MIS interbody fusion, oneshould keep in mind that cage placement may affect coronal and saggital balancenot only locally but also throughout the entire thoracolumbar spine, which couldaffect the long-term outcome of the entire fusion procedure.

n MYOFASCIAL PAIN SYNDROMES

A small subset of patients present with persistent or new onset of low-back painfollowinganMIS lumbar fusionprocedure.Often, these symptomsdevelopmore thansix months postoperatively after patients have recovered and have gained enoughfunctional improvements to produce a new onset of myofascial low-back pain.

In the author’s own series of 85 patients with TLIF at the levels betweenL3–L4 and L5–S1, 36 patients were diagnosed with myofascial low-back pain, and24 of these underwent removal of their spinal instrumentation between 9 and 15months postoperatively. Patients presented with symptoms of painful spinalinstrumentation. Their spinal construct was tender to palpation. Their symptomsresponded well to trigger point injections. Implant removal was considered only inpatients who did not respond well to conservative management, which consistedof physical therapy, anti-inflammatory medication, and local trigger pointinjections. All the 24 patients who underwent hardware removal improved andtheir symptoms resolved.

The author can only speculate why patients with lumbar MIS fusion surgeryseemingly have a higher rate of myofascial low-back pain than patients under-going open lumbar fusion procedures. However, a plausible explanation could bethat minimally invasive procedures are believed to result in less scar tissueformation. This has been demonstrated by a number of MRI studies that showedless fatty muscle degeneration and improved trunk control with percutaneouslyplaced pedicle screws versus open placement of pedicle screws. Q3There issignificantly less scare disuse formation. The good response rate followinghardware removal is supportive of this hypothesis.

n SUMMARY

There are many mostly technique-related issues with minimally invasive lumbarfusion procedures that may affect long-term results. Therefore, the novice surgeon

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should be familiar with them. Adequate decompression of neural elements,restoration of coronal and saggital balance, and attention to detail during theinterbody fusion are essential for good clinical outcomes that will stand the testof time.

n REFERENCES

1. Hilton DL Jr. Minimally invasive tubular access for posterior cervical foraminotomywith three-dimensional microscopic visualization and localization with anterior/posterior imaging. Spine J 2007; 7(2):154–158. Epub, September 11, 2006.

2. Santiago P, Fessler RG. Minimally invasive surgery for the management of cervicalspondylosis. Neurosurgery 2007; 60(Suppl 1):S160–S165.

3. Hong WJ, Kim WK, Park CW, et al. Comparison between transuncal approach andupper vertebral transcorporeal approach for unilateral cervical radiculopathy—apreliminary report. Minim Invasive Neurosurg 2006; 49(5):296–301.

4. Musacchio M, Patel N, Bagan B, Deutsch H, Vaccaro AR, Ratliff J. Minimally invasivethoracolumbar costotransversectomy and corpectomy via a dual-tube technique:evaluation in a cadaver model. Surg Technol Int 2007; 16:221–225.

5. Son-Hing JP, Blakemore LC, Poe-Kochert C, Thompson GH. Video-assisted thoraco-scopic surgery in idiopathic scoliosis: evaluation of the learning curve. Spine 2007; 32(6):703–707.

6. Barrenechea IJ, Fukumoto R, Lesser JB, Ewing DR, Connery CP, Perin NI. Endoscopicresection of thoracic paravertebral and dumbbell tumors. Neurosurgery 2006; 59(6):1195–1201.

7. Holly LT, Schwender JD, Rouben DP, Foley KT. Minimally invasive transforaminallumbar interbody fusion: indications, technique, and complications. Neurosurg Focus2006; 20(3):E6. Review.

8. Houten JK, Post NH, Dryer JW, Errico TJ. Clinical and radiographically/neuroimagingdocumented outcome in transforaminal lumbar interbody fusion. Neurosurg Focus2006; 20(3):E8.

9. Schwender JD, Holly LT, Rouben DP, Foley KT. Minimally invasive transforaminallumbar interbody fusion (TLIF): technical feasibility and initial results. J Spinal DisordTech 2005; 18(Suppl):S1–S6.

10. Park Y, Ha JW. Comparison of one-level posterior lumbar interbody fusion performedwith a minimally invasive approach or a traditional open approach. Spine 2007; 32(5):537–543.

11. Delamarter RB, Fribourg DM, Kanim LE, Bae H. ProDisc artificial total lumbar discreplacement: introduction and early results from the United States clinical trial. Spine2003; 28(20):S167–S175.

12. Potter BK, Freedman BA, Verwiebe EG, Hall JM, Polly DW Jr, Kuklo TR. Transforaminallumbar interbody fusion: clinical and radiographic results and complications in 100consecutive patients. J Spinal Disord Tech 2005; 18(4):337–346.

13. Harris BM, Hilibrand AS, Savas PE, et al. Transforaminal lumbar interbody fusion: theeffect of various instrumentation techniques on the flexibility of the lumbar spine. Spine2004; 29(4):E65–E70.

14. Coe JD. Instrumented transforaminal lumbar interbody fusion with bioabsorbablepolymer implants and iliac crest autograft. Neurosurg Focus 2004; 16(3):E11.

15. Kumar MN, Jacquot F, Hall H. Long-term follow-up of functional outcomes andradiographic changes at adjacent levels following lumbar spine fusion for degenerativedisc disease. Eur Spine J 2001; 10(4):309–313.

16. Louis-Ugbo J, Murakami H, Kim HS, Minamide A, Boden SD. Evidence ofosteoinduction by Grafton demineralized bone matrix in nonhuman primate spinalfusion. Spine 2004; 29(4):360–366.

17. Damien CJ, Grob D, Boden SD, Benedict JJ. Purified bovine BMP extract and collagenfor spine arthrodesis: preclinical safety and efficacy. Spine 2002; 27(Suppl 1):S50–S58.

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18. Sandhu HS, Khan SN, Suh DY, Boden SD. Demineralized bone matrix, bonemorphogenetic proteins, and animal models of spine fusion: an overview. Eur Spine J2001; 10(Suppl 2):S122–S131.

19. Martin GJ Jr, Boden SD, Titus L, Scarborough NL. New formulations of demineralizedbone matrix as a more effective graft alternative in experimental posterolateral lumbarspine arthrodesis. Spine 1999; 24(7):637–645.

20. Khan SN, Lane JM. The use of recombinant human bone morphogenetic protein-2(rhBMP-2) in orthopaedic applications. Expert Opin Biol Ther 2004; 4:741–748.

21. Riley EH, Lane JM, Urist MR, Lyons KM, Lieberman JR. Bone morphogenetic protein-2:biology and applications. Clin Orthop Relat Res 1996; 39–46 Q4.

22. Sandhu H. Spinal fusion using bone morphogenetic proteins. Orthopedics 2004; 27:717–718.

23. Szpalski M, Gunzburg R. Recombinant human bone morphogenetic protein-2: a novelosteoinductive alternative to autogenous bone graft? Acta Orthop Belg 2005; 71:133–148.

24. Walker DH, Wright NM. Bone morphogenetic proteins and spinal fusion. NeurosurgFocus 2002; 13:e3.

25. Mummaneni PV, Pan J, Haid RW, Rodts GE. Contribution of recombinant human bonemorphogenetic protein-2 to the rapid creation of interbody fusion when used intransforaminal lumbar interbody fusion: a preliminary report. Invited submission fromthe Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2004.J Neurosurg Spine 2004; 1:19–23.

26. BMP 2—Genetics Institute/Medtronic-Sofamor Danek/Integra. Bone morphogeneticprotein 2—Genetics Institute/Medtronic-Sofamor Danek/Integra, INFUSE Bone Graft,recombinant human bone morphogenetic protein 2—Genetics Institute/Medtronic-Sofamor Danek/Integra, RhBMP 2—Genetics Institute/Medtronic-Sofamor Danek/Integra. BioDrugs 2002; 16:376–377.

27. Stevens KJ, Spenciner DB, Griffiths KL, et al. Comparison of minimally invasive andconventional open posterolateral lumbar fusion using magnetic resonance imaging andretraction pressure studies. J Spinal Disord Tech 2006; 19(2):77–86.

28. Wang JC, Mummaneni PV, Haid RW. Current treatment strategies for the painfullumbar motion segment: posterolateral fusion versus interbody fusion. Spine 2005; 30(Suppl):S33–S43. Review.

29. Thalgott JS, Chin AK, Ameriks JA, et al. Minimally invasive 360 degrees instrumentedlumbar fusion. Eur Spine J 2000; 9(Suppl 1):S51–S56.

30. Singh K, Smucker JD, Gill S, Boden SD. Use of recombinant human bone morphogeneticprotein-2 as an adjunct in posterolateral lumbar spine fusion: a prospective CT-scananalysis at one and two years. J Spinal Disord Tech 2006; 19(6):416–423.Erratum in:J Spinal Disord Tech 2007; 20(2):185.

31. Barrey C, Jund J, Noseda O, Roussouly P. Sagittal balance of the pelvis-spine complexand lumbar degenerative diseases. A comparative study about 85 cases. Eur Spine J2007 Q5.

32. Roussouly P, Gollogly S, Berthonnaud E, Labelle H, Weidenbaum M. Sagittal alignmentof the spine and pelvis in the presence of L5–S1 isthmic lysis and low-gradespondylolisthesis. Spine 2006; 31(21):2484–2490.

33. Roussouly P, Gollogly S, Noseda O, Berthonnaud E, Dimnet J. The vertical projection ofthe sum of the ground reactive forces of a standing patient is not the same as the C7plumb line: a radiographic study of the sagittal alignment of 153 asymptomaticvolunteers. Spine 2006; 31(11):E320–E325.

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FROM THE FOREWORD . . .“With surgical techniques being the emphasis, a broad range of clinicians can effectivelyimplement various aspects of the book’s contents. Minimally Invasive Spinal FusionTechniques is thus a welcome addition to the professional literature to help advance the surgical understanding and continued progress of this exciting and fast moving field.”

— Dr. Heinz Michael Mayer, Orthopedic Hospital (Müchen, Germany)

ABOUT THE BOOK . . .Several surgery technologies have recently emerged which have led many Spinal Surgeons torethink traditional approaches to reconstructive procedures of the spine. Minimally invasivespinal surgery (MISS) techniques are now aided by computerized navigation systems, alongwith improved and more flexible instrumentation and surgical systems. Minimally InvasiveSpinal Fusion Techniques provides the medical professional with a thorough review of preclin-ical and clinical data while describing and illustrating the most effective surgical techniquesthus far employed. Objectively reviewing the most current treatment methods for patients withdegenerative conditions of the cervical and lumbar spine, this timely reference book spans thebreadth of minimally invasive spinal fusion and related methodologies that have been performed surgically to date, as well as its future as an ongoing medical treatment.

ABOUT THE EDITORS . . .Kai-Uwe Lewandrowski is a Clinical Assistant Professor at the University of Arizona and isin private practice at the Center for Advanced Spinal Surgery of Southern Arizona in Tucsonspecializing in MISS treatments for degenerative conditions, tumor, and trauma. He receivedhis MD from Humboldt University (Berlin, Germany), completed a residency at MassachusettsGeneral Hospital, and a fellowship in Spinal Surgery at the Cleveland Clinic. Dr. Lewandrowskihas served as lead Editor on such medical books as Advances in Spinal Fusion (2003) andSpinal Reconstruction (2006).

Christopher A. Yeung is a practicing Orthopedic Spine Surgeon at the Arizona Institute for Minimally Invasive Spine Care in Phoenix where he specializes in MISS techniques, especially relating to sports related spine injuries. Dr. Yeung received his MD from Universityof Southern California, completed a Orthopedic residency at UC-Irvine, and a Spine fellow-ship at UC-San Diego.

Mark J. Spoonamore is Assistant Professor of Clinical Orthopedic Surgery at the Universityof Southern California in Los Angeles where he specializes in MISS, as well as sports spinalinjuries and rehabilitation. Dr. Spoonamore received his MD from the University of Illinois atChicago, completed an Orthopedic Surgery residency at the University of Iowa, and a SpineSurgery fellowship at USC.

Robert F. McLain is on the staff of the Department of Orthopedic Surgery at the ClevelandClinic Foundation (Cleveland, Ohio). He is a well published authority regarding both micro-surgical and minimally invasive spine techniques. Dr. McLain serves as Associate Editor forthe journal, Spine. Prior to joining Cleveland Clinic in 1997, Dr. McLain was the Director of theSpine Care Center at UC-Davis.

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Binder2 KUL MIS Book