Evidence Basis/Outcomes inMinimally Invasive SpinalScoliosis Surgery

Neel Anand, MD, Mch Ortha,*, Eli M. Baron, MDb,Sheila Kahwaty, PA-Cc

KEYWORDS

� Adult scoliosis � Minimally invasive spine surgery � Evidence basis � Outcomes

KEY POINTS

� Minimally invasive spinal surgery (MISS) scoliosis correction may allow for adult scoliosis correctionwith significantly less tissue destruction and less blood loss than open procedures.

� MISS scoliosis correction without osteotomies has limits using present technologies in terms ofcorrecting sagittal plane deformity and has a ceiling effect of about 40� of coronal Cobb correction.

� MISS scoliosis correction has a different complication profile from traditional open scoliosis correc-tion; this may be largely reflective of the use of the lateral transpsoas approach and reduced bloodloss.

� Long-term level II and III studies are needed to compare outcomes between MISS and open adultscoliosis correction.

INTRODUCTION: NATURE OF THE PROBLEM

The principal goal of adult scoliosis surgery is ob-taining both sagittal and coronal balance of thespine.1 However, traditional scoliosis correctionhas been associated with high-volume blood lossand significant medical complications.2–4 Giventhis situation, minimally invasive spinal surgery(MISS) for the treatment of adult scoliosis is partic-ularly attractive. MISS techniques have been usedfor the treatment of lumbar degenerative scoliosis,iatrogenic scoliosis, and adult idiopathic scoliosis.Theoretically, blood loss can be limited, and med-ical complication rates can possibly be reducedwith less invasive procedures. Nevertheless, clin-ical and radiographic outcomes of MISS scoliosiscorrection need to be comparable with open sur-gery before recommending widespread adoption

a Department of Surgery, Spine Trauma, Spine Center,Boulevard, Suite 800, Los Angeles, CA 90048, USA; b

Sinai Medical Center, 444 South San Vicente Boulc Department of Surgery, Spine Center, Cedars Sinai Me800, Los Angeles, CA 90048, USA* Corresponding author.E-mail address: neel.anand@cshs.org

Neurosurg Clin N Am 25 (2014) 361–375http://dx.doi.org/10.1016/j.nec.2013.12.0141042-3680/14/$ – see front matter � 2014 Elsevier Inc. All

of these techniques for the treatment of adultscoliosis. MISS principles and surgical techniquesused in MISS scoliosis correction are reviewed inthis article, as well as outcomes, complications,and limitations of this rapidly evolving area of spi-nal surgery.

THERAPEUTIC OPTIONS OR SURGICALTECHNIQUE(S)

Indications for adult scoliosis correction includedeformity progression, sagittal or coronal imbal-ance with unremitting back pain, radiculopathy onthe side of the concavity of the curve caused byforaminal stenosis, lumbar hyperlordosis, patientswith a history of flat-back syndrome and backpain, fixed lateral listhesis within the degenerativecurve when motion is present on side-bending

Cedars Sinai Medical Center, 444 South San VicenteDepartment of Neurosurgery, Spine Center, Cedarsevard, Suite 800, Los Angeles, CA 90048, USA;dical Center, 444 South San Vicente Boulevard, Suite

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films, and when extensive decompressionincluding facetectomy or the violation of the parsis planned.5 A relative indication is progressivelyworsening deformity with pain as the rib cage abutsthe pelvis.In our practice, adult patients who undergo

MISS scoliosis surgery are typically being treatedfor symptomatic back and leg pain (Fig. 1). Thesepatients include those with adult idiopathic scoli-osis, iatrogenic scoliosis, and lumbar degenerativescoliosis. Patients have tried numerous conserva-tive measures, including physical therapy andepidural and facet injections, before being consid-ered for surgery. The main indication for correctionof adult scoliosis is mechanical low back pain. Thispain is typified by stiffness in the morning, withprogressive worsening of pain with activity that in-creases throughout the day. Often, but not always,this pain may be accompanied by radiculopathy orclaudication.6

Themain principle of adult scoliosis correction isachieving a balanced spinal alignment and ad-dressing symptomatic levels. Radiographic evalu-ation of the patient with adult deformity, whetherbeing treated with traditional open correction orMISS, involves measurement of the Cobb anglein the coronal plane, the amount of correction on

side-bending films, and the amount of deviationof the apical vertebrae to the central sacral verticalline.7 In the sagittal plane, a plumb line is drawnfrom the center of the C7 vertebra to the sacrum.Normally, this line should be within 5 cm of theposterior aspect of the sacrum. In addition,regional alignment and pelvic parameters, suchas pelvic incidence and pelvic tilt, are calculated.In planning for adult scoliosis, the patient’s symp-toms, stenosis, and disk degeneration must beconsidered.Interbody fusion techniques are used to improve

lordosis, help correct lateral listhesis, and, poten-tially, increase fusion rates. For lumbar degenera-tive scoliosis, proximal fusions are typicallystopped at a stable vertebra.7 Others have advo-cated stopping at T10.8 In terms of where to beginand end a fusion, this topic has been discussed indetail elsewhere and is not the focus of thisarticle.7,9 If a thoracolumbar fusion is extendedto the sacrum, interbody fusion and pelvic fixationshould be considered.9

Segmental pedicle screw fixation allows forgreater pullout strength than previous generationinstrumentation systems (ie, hooks, cables).Pedicle screws may allow for shorter fusion lengthand less operative blood loss than hooks.7,10,11

Fig. 1. (A, B) Anteroposterior andlateral 91 cm (36-inch) films of a68-year-old man with a history ofback pain and leg pain refractory toconservative measures. He was notedto have lumbar degenerative scoliosiswith a curve measuring 37� from L1to L5, with the apex to the left.

MISS Scoliosis Surgery 363

Traditional scoliosis surgery allows for variousopen corrective maneuvers, such as derotation,vertebral coplanar alignment, and in situ rodbending.12–14 In addition, open surgery allows forboth structural interbody techniques and osteoto-mies to assist in further deformity correction, withthe creation of lumbar lordosis as needed.1,7

A systematic review of adult scoliosis surgeryshowed that adult scoliosis surgery is associatedwith long-term improvement in patient radio-graphic and clinical outcomes. At a mean follow-up of 3.6 years, average curve reduction wasnoted to be 40.7% and mean Oswestry DisabilityIndex (ODI) was reduced by 15.7.15 In terms ofscoliosis deformity correction, sagittal balanceimprovement seems to be the strongest predictorof improved clinical outcomes, with correction ofcoronal balance being a lesser factor.16

Open adult scoliosis correction has certain limi-tations. Medical complication rates associatedwith open adult deformity correction may be ashigh as 70%.2 Large volume blood loss is not un-usual in these complex procedures. Seo and col-leagues17 reported outcomes in 152 patientsolder than 20 years undergoing open adult scoli-osis correction. These investigators noted amean blood loss of 2855.8 mL � 1822.9 mL.Transfeldt and colleagues18 noted a mean bloodloss of 1538 mL in patients undergoing full fusionand decompression of their degenerative scolioticcurves. The population undergoing adult scoliosissurgery is often elderly, with significant medicalcomorbidities and high cardiac risk. Given this sit-uation, the decision to proceed operatively withadult surgical deformity correction in the olderpopulation must be made carefully.19 Consideringthese limitations, MISS options may be attractive ifsimilar results can be obtained with less blood lossand less tissue trauma.

MISS Scoliosis Correction

A portion of the morbidity associated with tradi-tional spinal surgery occurs because of muscledamage associated with exposure and retractionand subsequent muscular devascularization anddenervation.20–23 Tubular approaches for diskec-tomy, decompression, and minimally invasive sur-gery posterior fusion were developed to minimizethese complications.24–29 MISS interbody fusiontechniques followed. This was an important devel-opment, because interbody fusion may havehigher fusion rates than posterolateral fusion tech-niques.7,30 In addition, diskectomy and graftplacement may allow the achievement of anteriordeformity release and alignment.31–34 Current op-tions for MISS interbody fusion techniques include

transforaminal lumbar interbody fusion (TLIF), min-iopen and MISS anterior lumbar interbody fusion(ALIF), lateral transpsoas interbody fusion andthe presacral approach for interbody fusion (Axia-LIF) (Table 1). All of these options have subse-quently been used in MISS correction of adultscoliosis.35–41

The combined use of 3 techniques to facilitatecircumferential MISS scoliosis correction was re-ported in 2008.42 These techniques included thetranspsoas approach for diskectomy and inter-body fusion, the presacral approach for L5-S1fusion, and percutaneous pedicle screw and rodplacement. Percutaneous screw and rod place-ment has proved to be a major determinant ofcorrection of apical vertical translation, evenbeyond diskectomy and interbody fusion.6 Subse-quently, other series have reported outcomes us-ing a combination of MISS techniques for adultscoliosis.

Most articles reporting MISS scoliosis correc-tion rely heavily on the lateral transpsoasapproach. This factor allows the surgeon MISS ac-cess to the spine, where diskectomy, deformityrelease, and interbody fusion can be achieved formultiple levels with minimal tissue disruption. Thecurrent technique, as described by Luiz Pimentaand published by Ozgur and colleagues,43 buildson the experience of other historical approachesin which MISS techniques were used to achieveALIF.44–46 The techniques of Thalgott and col-leagues47 and that of McAfee and colleagues48

served as precursors to the current technique.The current technique does not rely on endoscopyor laparoscopy. It requires less specialized equip-ment and theoretically has less of a learning curve.The transpsoas approach has subsequently beenwidely adopted as a technique to achieve releaseof scoliotic curves and perform interbody fusion(Fig. 2).6,40,41,49,50 However, the lateral approachdoes place the lumbar plexus and genitofemoralnerve at risk for injury and is not without its owncomplication profile, reflected in Table 3.

The development of multilevel percutaneouslyplaced screws, with freehand rod passage, al-lowed for deformity correction and fixation withminimal tissue disruption.42 Percutaneous rodand screw placement results in substantially lessdisruption of the thoracolumbar fascia than opentechniques. This factor is clinically relevant,because the thoracolumbar fascia may be a majorstabilizer of the lumbosacral spine and pelvis.51

Percutaneous screw and rod placement hasproved to be crucial in the correction of apicalvertical translation, even beyond diskectomy andinterbody fusion.6 In addition, MISS screwtechniques have been developed to allow

Table 1MISS interbody fusion technique

Technique Advantages DisadvantagesSagittal and Coronal PlaneCorrection with Technique

TLIF Posterior approach fordiskectomy and interbodyfusion

Reduced risk for neurologicinjury/durotomy whencompared with posteriorlumbar interbody fusion

Potential for neurologicinjury and durotomy

Time consuming

In 1 large deformity series,change in local lordosisranging from –1.7� to 4�

depending on leveltreated. May havesuperior results to ALIF incorrection of AP lumbarcurve and fractionalcurves. Mean correctionof AP lumbar curvereported at 22.9� and APfractional lumbosacralcurve of 10.3�78

ALIF Large grafting surface,indirect neuroforaminaldecompression

Avoidance of spinal canal

Potential viscous/vascularinjury, often requiresapproach surgeon,potential sympatheticdysfunction/retrogradeejaculation

Superior sagittal correctionwhen comparedwith TLIF.In 1 large deformityseries, increase in locallordosis ranging from 2.5�

to 5.5� was noted withALIF, depending on leveltreated. Reducedcorrection of AP lumbarcurve and fractional curvewas noted whencompared with TLIF; 9.9�

for AP lumbar curve and3.3� AP correction forfractional lumbar curve78

Transpsoasinterbodyfusion

Efficient method ofachieving diskectomy,deformity release andinterbody fusion; reducedrisk of vascular/viscusinjury when comparedwith ALIF, large graftsurface, indirectforaminal decompression

Usually cannot beperformed at L5-S1,potential for thighdysesthesias, legweakness

Mean gain of 2.8� lordosisat each level of transpsoasinterbody fusion63

Controversial as to whetherglobal coronal alignmentis improved or not

Global sagittal balanceseems not improved withthis technique62,63

AxiaLIF Minimally invasive corridorto L5-S1

Cannot be performed incases of prerectal scarringor aberrant vasculature

Data not available

Abbreviation: AP, anteroposterior.

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supplemental iliac fixation, allowing rod insertionwithout connectors or extensive soft tissuedissection.52,53

In terms of achieving MISS fusion, series to datehave relied heavily on interbody grafting and theoff-label use of recombinant human bone morpho-genetic protein 2 (rhBMP-2) (Medtronic SofamorDanek, Memphis, TN) (Table 2). Use of rhBMP-2has facilitated fusion without the need for exten-sive posterolateral decortication or autogenousbone graft harvesting.

CLINICAL OUTCOMES

In the series mentioned earlier, reporting the com-bined use of 3 techniques for MISS correction ofscoliosis, outcomes for 12 patients were reported(Fig. 3).42 Mean segments operated on were 3.64.Mean blood loss for the transpsoas approach was164 mL, and for the posterior approach, includingpedicle screw placement and AxiaLIF, it was94 mL. Mean surgical time for anterior procedureswas 4 hours. Mean surgical time for posterior

Fig. 2. Anteroposterior fluoroscopic image showingCobb elevator being used to release contralateralannulus during a direct lateral interbody fusionprocedure.

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procedures was 3.9 hours. Mean preoperativeCobb was 18.93�. Mean postoperative Cobb was6.19�. Mean follow-up time was 75.5 days, withclinical improvement documented by a decreasein Visual Analogue Scale (VAS) of 4.8. Althoughthis study was primarily a feasibility studydescribing the usefulness of MISS techniques inthe correction of adult scoliosis, it was also the firststudy describing multilevel percutaneous screwand freehand rod placement. Subsequently,numerous other series regarding MISS for adultscoliosis have been published (see Table 2).

COMPLICATIONS AND CONCERNS

Complication rates and complications commonlyseen with MISS deformity correction may bedifferent from those seen with open correction ofadult spinal deformity (ASD). Complications notedwith MISS scoliosis series are summarized in(Table 3).

The complication rates in these series comparefavorably with open approach series for lumbardegenerative deformity, in which complicationrates of 20% to 80% have been reported.54–57

Cho and colleagues58 reported an overall compli-cation rate of 68% in patients undergoing posteriorfusion and instrumentation (in addition, 7 patientsunderwent posterior lumbar interbody fusion) fordegenerative scoliosis. These investigators notedan early complication rate of 30%, a mean bloodloss of 2.1 L, and a mean hospital stay of20.7 days. Similarly, Wu and colleagues59 noted

a mean blood loss of 1.7 L in 29 patients undergo-ing posterior lumbar interbody fusion for degener-ative scoliosis. In a study of 78 articles regardingfusion for lumbar degenerative conditions notedin degenerative scoliosis, Bono and Lee60 noteda pooled good to excellent outcome rate of 82%with fusion rates of 87%. However, these investi-gators noted a pooled complication rate of 55%.

Several concerns have been raised regardingMISS correction of adult scoliosis. All the seriesto date regarding MISS adult scoliosis correctionhave been classified as level IV data (see Table 2).Future level II or III studies may better answer howoutcomes compare with open surgery. To date,there has been no direct comparison with opensurgery in any trial.

Shaffrey and Smith61 noted several problemsregarding most series and outcomes data forMISS deformity correction. Most series reportoutcomes of less than 2 years, with limitedhealth-related quality of life data. Even althoughmore of these data have been reported,37 thereare still limited data regarding MISS deformitycorrection and its relationship to pelvic parame-ters, lumbar lordosis, and the sagittal verticalaxis (SVA). Thus, it is argued that a study needsto be conducted that meets the same standardused in the treatment of open deformity surgery.

Understanding limitations of current techniquesin achieving appropriate alignment is mandatorywhen using MISS technology for deformity correc-tion. Acosta and colleagues62 reviewed radio-graphic records of 36 patients undergoingtranspsoas diskectomy and interbody fusion forlumbar degenerative disease. Transpsoas diskec-tomy and interbody fusion was performed on anaverage of 1.8 levels per patient. SupplementalMISS posterior fixation was used in all but 1 pa-tient. Standing anteroposterior (AP) and lateral91 cm (36-inch) films were obtained preoperativelyand postoperatively for measurement of globalcoronal and sagittal balance. AP and lateral lum-bar standing radiographs were obtained for mea-surement of segmental and regional sagittal andcoronal Cobb angles. The investigators notedtranspsoas interbody fusion to significantlyimprove segmental, regional, and global coronalplane alignment in these patients. However, theynoted that regional lumbar lordosis and globalsagittal alignment were not improved by thesetechniques. Similarly, Sharma and colleagues63

noted a mean gain of 2.8� (P<.001) of lordosis ateach level of transpsoas interbody fusion but nosignificant change in the overall coronal or sagittalplane alignment of the lumbar spine.

Recently, Johnson and colleagues64 reportedon pelvic parameters and sagittal balance after

Table 2MISS scoliosis series

Author, YearNumber ofPatients

Length ofFollow-Up Blood Loss Radiologic/Clinical Outcomes Comments

Level ofEvidence

Anandet al,42 2008

12 75.5 d 164 mL for transpsoasapproach; 94 mL forposteriorinstrumented fusionand AxiaLIF

Decrease in mean Cobb from 18.93�

to 6.19�

Mean decrease in VAS of 4.8

Retrospective, feasibility study usinga combination of the transpsoaslateral approach for diskectomyand interbody fusion, AxiaLIF, andpercutaneous pedicle screw androd placement. Mean segmentsoperated on was 3.64

rhBMP-2 was used for all fusion sitesPosterolateral fusion at all fusionsites without interbody fusion andat L5-S1

IV

Anandet al,38 2010

28 22 mo 241 mL for transpsoasapproach; forposterior procedures(including pediclescrew and rodplacement andAxiaLIF) was 231 mL

Decrease in mean Cobb from 22� to7�

ODI improved from 39.13 to 7 VASimproved from 7.05 to 3.03

All patients were noted to maintaincorrection of their deformity andnoted to have arthrodesis on plainradiograph

Retrospective study. MISS correctionand fusion over 3 or more levelsfor adult scoliosis. Combination ofthe transpsoas lateral approachfor diskectomy and interbodyfusion, AxiaLIF (if fusing to L5-S1),and percutaneous pedicle screwand rod placement rhBMP-2 wasused for all fusion sites.Posterolateral fusion at all fusionsites without interbody fusion

IV

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Anandet al,37 2013

71 39 mo Patients with 1-stagesame-day surgery hada mean blood loss of412 mL. Patients with2-stage surgery had amean blood loss of314 mL for transpsoasinterbody fusion and357 mL for posteriorinstrumentation andaxial lumbarinterbody fusion

Mean number of levels operated onwas 4.4. Mean hospital stay was7.6 d (mean preoperative Cobbangle was 24.7�, which correctedto 9.5�. Mean preoperativecoronal balance was 25.5 mm,which corrected to 11 mm. Meanpreoperative sagittal balance was31.7 mm and corrected to10.7 mm. Mean preoperativelumbar apical vertical translationwas 24 mm and corrected to12 mm. Fusion rate, as assessed byCT scan was 94%. VAS, ODI, andSF-36 improved significantly:preoperatively, 6.43, 50.3, and41.8; at last follow-up, 2.35, 41,and 62.7, respectively

Retrospective study. MISS correctionand fusion over 2 or more levelsfor adult scoliosis. Combination ofthe transpsoas lateral approachfor diskectomy and interbodyfusion, AxiaLIF (if fusing to L5-S1),and percutaneous pedicle screwand rod placement rhBMP-2 wasused for all fusion sites.Posterolateral fusion at all fusionsites without interbody fusion

IV

Caputoet al,39 2012

30 1 y ODI decreasing from24.8% to 19.0% andVAS leg pain scoredecreasing from 5.4to 2.8

Mean Cobb 20.2 preoperativelyPostoperatively not reportedMean ODI decreased from 24.8 to

19.0. Mean VAS back decreased;mean VAS leg decreased from 6.8to 4.6

Patients underwent the transpsoasapproach followed by posteriorMISS instrumentation for adultdegenerative scoliosis. Osteocellused for interbody fusion(Nuvasive, San Diego, CA)

IV

Dakwaret al,40 2010

25 80% ofpatientsunderwentmore than6 mo offollow-up

53 mL per segmentfused

Decrease in mean Cobb from 22.1�

to 6.2�. Mean improvement of 5.7points on the VAS scores and a23.7% improvement in ODI. Allpatients with >6 mo follow-upwith solid fusion

Patients with adult degenerativedeformity. Avariety of stabilizationtechniques were used, includinglateral plates, and open andpercutaneously placed pediclescrews. At each level, rhBMP-2,tricalciumphosphate, andhydroxy-apatite used as fusion material

IV

Isaacset al,79 2010

107 6 wk Almost two-thirds(62.5%) of patientshad a recorded bloodloss of 100 mL, andonly 9 patients (8.4%)had a 300 mL bloodloss

NA Multicenter prospective,nonrandomized study oftranspsoas lumbar interbodyfusion procedures in adultdegenerative scoliosis.Perioperative outcome study.Fusion material not specified

IV

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Table 2

(continued)

Author, YearNumber ofPatients

Length ofFollow-Up Blood Loss Radiologic/Clinical Outcomes Comments

Level ofEvidence

Karikariet al,80 2011

22 patients, ofwhom 11 haddegenerativescoliosis

16.4 mo 227.5 mL In the subset of patients treated fordegenerative scoliosis, the meanpreoperative and postoperativecoronal Cobb angles were 22�

and 14�, respectively

Retrospective study. Most patientswithout supplemental fixation.Lateral screws in 4 patients.Posterior fixation in 1 patient. Allpatients treated for scoliosisreceived rhBMP-2 in their cages

IV

Scheufleret al,81,82 2010

30 patient withthoracolumbardegenerativekyphoscoliosis

19.6 mo 771.7 mL Fusion rate was 90% (26 patientsavailable for CT scan at a meanof 6 mo).

Average segmental correction of10�–12� in the coronal andsagittal planes. Mean lumbarsagittal Cobb angle correctionwas 44.8 � 10.7�, resulting in amean postoperative lumbarlordosis of �36 � 6.9�. Meanpreoperative sagittal balance of31.6 � 15.2 mm (range, 5–96 mm) was reduced by 63.5 �30% to a postoperative mean of8 � 8.4 mm (range, �4–25 mm).A mean coronal Cobb anglecorrection of 31.7 � 13.7� wassufficient to achieve a final meanpostoperative coronal Cobbangle of 10.3 � 7.8� at 12-mofollow-up. Mean preoperativeapical vertebral translation wasreduced from 22.3 � 32 mm(range, 17–78 mm) to 9.9 �15.6 mm (range, 8–30 mm).

Mean VAS reduced from 7.5 to 2.82at last follow-up; ODI decreasedfrom mean of 57.2 to 23.9

Retrospective series of patientsundergoing unilateral MISS TLIFsand percutaneous screw and rodplacement for MISSkyphoscoliosis correction usingbiplanar fluoroscopy orintraoperative CT scanning/navigation. 3 to 8 segmentsfused using TLIFs and facetfusion. TLIF performed usingtubular access. In patientsreceiving short instrumentation(�4 segments), TLIF wasperformed each level, whereas3–5 segments were treated byTLIF in patients undergoing longinstrumentation. Vertebralcement augmentationperformed in 10 femaleosteopenic patients. Autologousbone chips and rhBMP-2 wasused for all fusion sites

IV

Anandetal

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Sharmaet al,63 2011

43 patients, 25with lumbardegenerativescoliosis

1 y 200 mL fortranspsoasportion ofsurgery only

Mean correction of maximal Cobbangle was noted to be 10.4�

(43%). VAS, ODI, and SF-12improved significantly.Preoperatively, VAS and ODI 8.2and 42.6; at 1 y, 4.6 and 31.5,respectively

Retrospective study. Ten patients intheir series were treated withstand-alone transpsoas fusion, 9with lateral plate and screwfixation, and 24 with pediclescrew fixation. Depending onsurgeon preference, autograft orrhBMP-2 was used

IV

Wang andMummaneni,41

2010

23 13.4 mo 477 mL Decrease in mean Cobb from 31.4�

to 11.5�

Thoracolumbar lordosis increasedby a mean of 8�

All interbody fusions with solidarthrodesis as noted on CT scan.Two of 7 cases in whichposterolateral fusions wereperformed alone hadpseudarthrosis.

Significant improvements in VAS:VAS leg averaged 4.35 andimproved to 1.57; VAS backaveraged 7.30 and improvedto 3.35

Retrospective study. Two centers.Patients with scoliosis >20� orsignificant sagittaldecompensation with loss ofsagittal balance. Deformitycorrection using the transpsoasapproach, along with MISS TLIFat L5-S1 if fused to the sacrum.rhBMP-2 was used for all fusionsites. Posterior fixation usingpercutaneous pedicle screws androds. Posterolateral fusion at allfusion sites without interbodyfusion

IV

Abbreviations: CT, computed tomography; NA, not applicable; SF-12, Short Form 12 Health Survey; SF-36, Short Form 36 Health Survey; VAS, Visual Analog Scale.

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Fig. 3. (A, B) Anteroposterior andlateral postoperative images 3 yearsout from 3 stage MISS deformitycorrection, including AxiaLIF. Thepreviously described curve now mea-sures 8�. Coronal and sagittal balanceis maintained.

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transpsoas interbody fusion for lumbar degenera-tive conditions in patients with at least 6 months offollow-up. Standing preoperatively and postopera-tively lumbar radiographs were used in theirassessment. A total of 30 patients were includedin this series, with only 6 undergoing posterior sup-plemental fixation: 3 with pedicle screws and 3with interspinous process devices. Most patientsunderwent operations at a single level. The inves-tigators found no effect of the procedure on sacralslope or pelvic tilt. They found lumbar lordosis notto be significantly affected by lateral transpsoasinterbody fusion but Cobb angle to be significantlyreduced.Limitations exist in these studies, because the

lateral transpsoas approach is typically beingused for short segment deformity correction.Recent multicenter analysis of data through theInternational Spine Study Group and radiologicanalysis of our data suggest that there are ceilingeffects to both the amount of Cobb correction andthe SVA, which can be corrected using circumfer-ential MISS techniques (incorporating the lateraltranspsoas approach) in spinal deformity. A

ceiling effect of 34� of Cobb correction was notedin 1 multicenter study.65 Our study revealed aCobb ceiling effect of 40� and an SVA ceiling ef-fect of 10 cm.66 Hence, the techniques do notseem to provide major correction of global lumbarlordosis or sagittal plane deformity as seen in pro-cedures involving osteotomies. Because sagittalplane alignment is a critical parameter for out-comes in the setting of ASD,67 patients withconsiderable SVA imbalance or pelvic inci-dence/lumbar lordosis mismatch may be betterconsidered for appropriate osteotomy or otheropen techniques rather than relying solely onMISS techniques for sagittal plane deformitycorrection.Nevertheless, techniques continue to involve

and more lordosis may be obtainable in the futureusing the MISS technique. Deukmedjian and col-leagues68 reported a novel surgical technique bywhich release of the anterior longitudinal ligamentwas performed in addition to an MISS lateralretroperitoneal transpsoas approach. This tech-nique was performed to achieve an even greaterlordosis than a typical transpsoas approach. The

Table 3Complications reported in MISS adult scoliosis series

Author, Year Complications MISS Complication Rate

Anandet al,83 2013

3 quadriceps palsy (2 made a completerecovery within 6 mo)

1 foot drop after transpsoas approach ileusDeep venous thrombosisPulmonary embolism cerebral hemorrhage,

pleural effusion and underwentthoracentesis

Ureteropelvic injury, retrocapsular kidneyhematoma

Screw looseningSuperficial sacral wound dehiscence

28% complication rate

Caputoet al,39 2012

Lateral incisional breakdownPedicle fractureHerniaAtrial fibrillation2 cases of iatrogenic anterior longitudinal

ligament ruptureSubstantial amount of patients having thigh

numbness or pain, which all resolved by4 wk

26.6% complication rate

Dakwaret al,40 2010

Rhabdomyolysis, asymptomatic graftsubsidence, and asymptomatic hardwarefailure

3 patients with thigh numbness

NA

Isaacset al,79 2010

Myocardial infarction, sepsis, deep veinthrombosis, posterior wound infection,kidney laceration

Motor deficit

Major complication rate of 5.8%and minor complication rateof 11.5% for those with MISSposterior instrumentation;motor deficit rate of 6.5%

33.6% of patients were notedto have some evidence ofweakness after the transpsoasapproach (in 86.2% thisweakness was transient)

Scheufleret al,81 2010

13.3% with new nerve root motordisturbance

10% with worsening of preexistingneuropathic pain

5 patients with small durotomies43.3% of patients with instrumented fusion

to the sacrum with sacroiliac painMedical complications included deep venous

thrombosis, hemorrhage from an ulcer,and urinary tract infections

Major and minor complicationrates were 23.4% and 59.9%,respectively

Sharmaet al,63 2011

15 patients of 43 with thigh pain11 patients with hip flexor weakness4 patients with quadriceps weaknessNumerous end-plate fractures in patients

undergoing transpsoas interbody fusion2 vertebral body fractures in patients

undergoing lateral fixation1 case of infection at the site of posterior

instrumentationRetroperitoneal hemorrhage

NA

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Table 3

(continued)

Author, Year Complications MISS Complication Rate

Tormentiet al,49 2010

2 cases of motor weakness; 1 transientCecal perforation

NA75% of patients to have thighparesthesias or dysesthesias

Wang &Mummaneni,41

2010

Thigh numbness, pain, and weakness in 30.4%of patients undergoing the transpsoasapproach, on the same side of the approach

Cerebrospinal fluid leakage Hardware pulloutPneumothoraxOne case of significant blood loss

NA

Abbreviation: NA, not applicable.

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investigators reported good results in 7 patients, inwhom they noted an increase in global lumbarlordosis of 24�, segmental lordosis of 17� per levelof anterior longitudinal ligament release, and adecrease in pelvic tilt of 7�. They also noted adecrease in SVA of 4.9 cm. They noted that a mini-mally invasive lateral retroperitoneal transpsoasapproach in addition to release of the anterior lon-gitudinal ligament might be a feasible alternative incorrecting sagittal plane deformity. Wang andMadhavan69 reported using an MISS techniquein association with a miniopen approach for per-formance of pedicle subtraction osteotomy. Theseinvestigators described the technique as an evolu-tion of minimally invasive techniques now beingused for the treatment of fixed sagittal imbalance.Similarly, Wang70 described using a hybrid MISSapproach for deformity correction with goodlordosis restoration using a combination of unilat-eral multilevel facet osteotomies, TLIF, expand-able cages, and percutaneous screw/rodinstrumentation.From our experience, we advise in addition

against using these techniques in their presentform in cases of truly rigid scoliosis, for curvesgreater than 100� in magnitude, and for congenitaland neuromuscular deformities. Osteoporosiswith a T-score of less than –2.0 is also acontraindication.6

Other criticisms of MISS techniques in general,but specifically for deformity correction, include alarger learning curve than for open techniques,the need for specialized equipment, disorientationof the surgeon, and increased radiation expo-sure.26,71–73 With proper training and experience,the disadvantages of learning curve and equip-ment investment are reduced with time. Disorien-tation may be an issue with certain deformities,especially with suboptimal imaging or poor bonedensity. Surgeon radiation exposure remains a

serious concern regarding these procedures.When a technique is performed properly, adheringto radiation safety guidelines, many of these pro-cedures can be performed yearly withoutexceeding occupational dose limits.74 In addition,neuronavigation may be useful in increasing sur-geon accuracy with instrumentation placementand reducing radiation exposure.75–77

SUMMARY

MISS scoliosis surgical correction continues toevolve, and its use has increased in recent years.Theoretic advantages of these techniques overopen procedures include reduced blood loss,potentially reduced complication rates, andreduced tissue trauma. These techniques may beuseful in their present form when up to 40� of coro-nal Cobb correction is desired and with fixedsagittal imbalance less than 10 cm. Questionsremainas to thedurability of the resultsand towhichdeformities are better served with open correctionmethods. Although long-term follow-up has beenreported, more data are necessary to ensure thatthe results are comparable in the long-term withopen deformity correction. Future level II or IIIstudies should be designed to help answer whatis the role of MISS technologies in the setting ofscoliosis when compared with the open technique.

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