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2007;89:1874-1885. doi:10.2106/JBJS.G.00509J Bone Joint Surg Am.Michael H. Huo, Nathan F. Gilbert and Javad Parvizi What's New in Total Hip Arthroplasty

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COPYRIGHT 2007 BY THE JOURNALOF BONEAND JOINT SURGERY, INCORPORATED

1874

Specialty Update

Whats New in Total Hip ArthroplastyBy Michael H. Huo, MD, Nathan F. Gilbert, MD, and Javad Parvizi, MD

Introduction

Total hip arthroplasty continued to receive much attentionduring the past year. The demand for total hip arthroplastycontinues to increase. Following the outlines from previousupdates, this years review is organized in the following sec-tions: (1) epidemiology and public health, (2) clinical out-come of primary total hip arthroplasty, (3) clinical outcome ofrevision total hip arthroplasty, (4) current status of minimal

incision total hip arthroplasty, (5) hip resurfacing, (6) compli-cations, (7) bearing surfaces, and (8) other clinical and scien-tific studies.

Epidemiology

Resource utilization in total hip arthroplasty has continued toescalate because of the increase in the number of patients un-dergoing arthroplasty. Vessely et al., using the age-adjusteddatabase of residents of a single United States county, reporteda 55% increase in the number of total hip arthroplasties be-tween the years 1969 through 1975 and 2000 through 2003.Women had higher utilization rates than men did. The largestincrease was for patients who were less than fifty years old.

The burden and resource utilization associated with revisiontotal hip arthroplasties are even greater. Ong et al. quantifiedthe projected economic burden of revision total hip arthro-plasty and total knee arthroplasty. Medicare (1997 to 2004)and United States census data were incorporated into a Pois-son regression model to determine the projected economicburden through 2015 for both hospitals and surgeons. On thebasis of their analysis, the annual hospital and surgeon chargesfor primary total hip arthroplasty in the United States arelikely to increase to $17.7 billion and $1.9 billion, respectively.Revision total hip arthroplasty poses a greater economic bur-den than revision total knee arthroplasty does. Using the Na-

tionwide Inpatient Sample (NIS), which includes a survey ofapproximately 1000 hospitals and the computation of the fu-ture population size, Kurtz et al. predicted that periprostheticinfection has the potential to be the most dominant reason forthe failure of total joint arthroplasty in the United States overthe next two to three decades. Suboptimal outcomes and com-plications associated with these procedures will result in aneven greater burden on society.

Zhan et al.1 screened more than eight million hospitaldischarge records in 2003 and identified approximately200,000 total hip arthroplasties, 100,000 partial hip arthro-plasties, and 36,000 revision total hip arthroplasties. Sixtypercent of the patients were more than sixty-five years ofage, and 75% had at least one medical comorbidity. The in-hospital mortality rates for the three procedures were 0.33%,3.04%, and 0.84%, respectively. With respect to complica-tions, the rates of infection were 0.05%, 0.06%, and 0.25%,respectively, and the rates of venous thromboembolism were0.68%, 1.36%, and 1.08%, respectively. The rates of readmis-sion within ninety days for any reason were 8.94%, 21.14%,and 15.72%, respectively, and the rates of readmission within

ninety days for problems related to the hip were 2.15%,1.61%, and 3.99%, respectively. Advanced age and an in-creased number of medical comorbidities were the mostpredictive of mortality and complications. Finally, the meanhospital charges were $34,951, $35,985, and $46,849, respec-tively, in 2003 dollars.

A study from the Swedish hip arthroplasty registry alsoidentified comorbidities as an important parameter influenc-ing the outcome. That study on 4055 total hip arthroplastiesfrom thirty-seven different centers demonstrated that patientanxiety/depression was a very important predictor of out-come. Some researchers have investigated the effects of delayin performing surgery on the outcome of total hip arthro-

plasty. Garbuz et al.

2

conducted a prospective study of 201patients who were on a surgical waiting list for total hip ar-throplasty to specifically determine whether waiting for sur-

Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor amember of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercialentity. A commercial entity (Stryker Orthopaedics) paid or directed in any one year, or agreed to pay or direct, benefits in excess of $10,000 to a re-search fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which one or more of the authors, or amember of his or her immediate family, is affiliated or associated.

J Bone Joint Surg Am. 2007;89:1874-85 doi:10.2106/JBJS.G.00509

Specialty Update has been developed in collaboration with the Council ofMusculoskeletal Specialty Societies (COMSS) of the American Academy ofOrthopaedic Surgeons.


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THE JO U R N A L O F BON E & JOINT SU R G E R Y J B J S .OR G

VO L U M E 89-A NU M B E R 8 AU G U S T 2007

WH AT S NEW IN TO T A L HIP AR T H R O P L A S T Y

Whats New in Total Hip Arthoplasty

gery would result in a less successful outcome. They foundthat waiting time was strongly associated with a reduced prob-

ability of a better-than-expected outcome after total hip ar-throplasty. There was an 8% reduction in outcome with everyadditional month of waiting. They also found the strongestassociation of a worse outcome in patients with more pain,lower function, and more hip stiffness preoperatively. Roderet al.3 performed a retrospective cohort study evaluating theassociation between preoperative functional status and post-operative outcome. Those investigators reviewed 13,766 totalhip arthroplasties that had been prospectively entered into amulti-nation registry (International Documentation andEvaluation System [IDES]) from 1967 to 2002. They found astrong association between both preoperative walking timeand hip flexion arc and the postoperative outcome. Most im-portantly, the preoperative pain level did not have an impact

on the postoperative pain relief. It is hoped that data fromstudies such as these will enable the clinician to select patientsat least partially on the basis of predictors of good outcome.Given an expected reduction in resources, prioritization fortotal hip arthroplasty may ultimately reduce utilization.

Clinical Outcome of Primary

Total Hip Arthroplasty

StemThe evolution favoring cementless fixation of the femoralcomponent continues as the long-term results of unce-mented components become available. Engh et al. reportedthe twenty-year follow-up results of the initial series of 223

total hip arthroplasties performed with use of the extensivelycoated AML stem (DePuy, Warsaw, Indiana). The mean age atthe time of surgery was fifty-five years. The mean durationfollow-up for the 130 living patients (136 stems) was 19.2

years. Only three stems were revised because of loosening.Fibrous-stable fixation of the stem was observed in anotherthree hips. The rate of stem survival free of any revision wasestimated to be 97.2% at twenty years.

Reports of the long-term outcome associated with thetapered wedge-shaped femoral stem are also becoming avail-able. McLaughlin and Lee reported the twenty-year results of145 total hip arthroplasties that had been performed with a ta-pered stem. No stem was revised because of loosening. Among

the stems that remained in situ, 96% demonstrated osseousfixation, 3% demonstrated stable fibrous fixation, and 1%demonstrated radiographic loosening. The rate of revision be-cause of infection was 4%. The rate of survival was estimatedto be 91% at twenty-two years.

The use of stem designs with a higher offset has in-creased because of their ability to better restore the anatomy,increase abductor efficiency, reduce joint-reaction forces,and minimize impingement. Some have questioned if theincreased offset would result in a higher prevalence of tro-chanteric bursitis, thigh pain, and stem loosening. Berend etal. compared two groups of forty-nine consecutive total hip

arthroplasties that had been performed by the same surgeonswith use of identical stem geometry, surface texture, and sur-

gical techniques. One group had increased stem offset. Themean duration of follow-up was thirty-eight months for thehigh-offset group and forty-six months for the normal-offsetgroup. The investigators found lower rates of bursitis (6%compared with 12%; p < 0.05) and thigh pain (0% comparedwith 6%; p < 0.05) in the high-offset group. Moreover, limb-length discrepancy was observed in only one patient in thehigh-offset group, compared with six patients in the normal-offset group. The authors believed that more accurate restora-tion of femoral offset and soft-tissue tension resulted in thebetter results.

CupThe durability of cementless cup fixation has been well docu-

mented. Aseptic cup failure principally has been due to articu-lation wear and associated osteolysis. Short-term failure hasbeen due to hip joint instability. A lateralized cup liner offersthe surgeon the option to restore the hip center and reducesthe risk of impingement from the femoral stem. In the studyby Burke et al.4, fifty-six total hip arthroplasties that had beenperformed with a 4-mm lateralized liner were compared withthirty-nine total hip arthroplasties that had been performedwith use of a neutral liner. At a mean duration of follow-up of7.1 years, there was a significant increase in polyethylene wear(0.04 mm/year) in association with the lateralized liners (p =0.02). The dislocation rate was lower (3.6% compared with10.3%), but not statistically so, for the lateralized liner. There

was no difference between the groups with regard to the fixa-tion status of the shell. The wear characteristics of lateralizedliners need to be further studied.

Clinical Outcome of

Revision Total Hip Arthroplasty

Stem RevisionContinuing efforts have been made to use newer techniquesand implant designs in the hope of improving the success ofrevision total hip arthroplasty. It appears that the newer gen-eration of modular fluted stems, with a reinforced taper junc-tion, may be a better choice for reconstruction of the femur inpatients with bone loss. Even the advocates of monoblock, ex-

tensively coated stems have reported a better outcome in asso-ciation with the use of modular stems. Paprosky, in a study ofthirty-two patients, reported the outcome of revision total hiparthroplasty with use of a modular tapered stem after a meanduration of follow-up of 5.3 years. The mean stem diameterwas 21 mm (range, 17 to 26 mm). All revisions were per-formed through an extended trochanteric osteotomy. Femo-ral bone deficiencies were classified as Paprosky type IIIA intwo hips, type IIIB in twenty-three hips, and type IV in sevenhips. One stem was revised because of infection, and one wasrevised because of loosening. One additional stem had subsid-ence but was not revised. The author concluded that the mod-


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ular tapered stems performed better than did the extensivelycoated stems, particularly when there was marked femoral

bone deficiency. Garbuz et al.

5

, in a matched-pair analysis inwhich a monoblock extensively coated femoral stem was com-pared with a modular fluted stem, also noted a better outcomein terms of pain, function, and overall rating in the group ofpatients who received the modular, tapered stem. One majorproblem of the latter study was that some important parame-ters such as operating time, blood loss, surgical approach, useof the extended trochanteric osteotomy, bone-grafting, con-comitant cup revision, and preoperative functional statuswere not matched.

The modular stem does, however, pose a potential prob-lem. Surgeons and engineers have long been concerned withthe potential for corrosion and fretting at taper junctions inmodular implant designs, leading to reduction in fatigue

strength and the potential for catastrophic failure of the im-plant. Furthermore, the generation and migration of frettingand corrosion products could add to the particulate burdenand lead to accelerated bearing surface wear from third-bodyabrasion. Jacobs et al. performed a detailed analysis of thirtyretrieved modular stems of three different designs. Frettingand corrosion damage were observed at the stem-sleeve orstem-body junction in twenty of thirty stems. Qualitativegrading revealed that the damage was minimum in ten, mildin eleven, moderate in six, and severe in three. Fortunately, se-vere changes resulting in a potential risk for structural failureof the stem were observed in only one hip.

Cup RevisionAcetabular revision in the presence of bone deficiency is tech-nically challenging. In the study by Weeden and Paprosky6,134 consecutive revisions that had been performed with useof a porous-coated cup with peripheral screws were followedfor a mean of 13.2 years. Bone deficiency was classified asPaprosky type I or II in 80% of the hips and as type IIIA in20%. There was no case of pelvic discontinuity. No structuralbulk graft was used. Ninety-five percent of the hips were stableand were rated as clinically successful. Seven hips failed: fivebecause of infection and two because of aseptic cup loosen-ing. The most common complication was dislocation (preva-lence, 4%), despite the fact that all patients used an abduction

orthosis for six weeks postoperatively. Weeden and Schmidtreported the outcome of revision with use of a trabecular ace-tabular cup in a study of forty-three hips with severe bone de-ficiency (classified as Paprosky type IIIA in thirty-three hipsand as type IIIB in ten). Modular trabecular metal augmentswere used in twenty-six hips (60%) to provide additional sup-port for the cup. After a mean duration of follow-up of 2.8

years, one cup had failed because of infection. There were noadditional instances of revision or loosening.

Jumbo cups and pelvic reinforcement cages have alsobeen used for reconstruction of the acetabulum in hips withmarked bone loss. While both methods have been associated

with failures, a combination technique known as the cageover cup technique is believed to be a viable option for chal-

lenging acetabular revision cases. The proposed advantagesof this combination are that (1) the porous cup will allow forlong-term durability of fixation by osseous ingrowth to thehost, and (2) the cage will protect the cup, which may havefailed in the short term because of poor host-bone quantityand quality. Noiseux et al. reported the results of this combi-nation technique in a study of thirty-one complex revisions.The acetabulum was reconstructed with use of a hemispheri-cal shell, over which a cage was placed, and the polyethyleneliner was cemented into the cage, thus unitizing the entirecomposite. The mean duration of follow-up was 2.3 years. Norevision was done for the treatment of loosening. Radiolucentlines were observed in 42% of the hips, especially over the is-chial flange of the cage. Partial bone-graft resorption occurred

in 26% of the hips. Revision was necessary in two hips for thetreatment of recurrent dislocation. Eighty-two percent of thehips were rated good to excellent. Longer-term follow-up isnecessary to determine if this new technique will be more du-rable than either a jumbo cup or a cage alone.

Controversies exist with regard to the best way to ad-dress pelvic osteolysis around stable cups. Engh et al. injecteda semi-liquid calcium sulfate bone graft substitute to fill pelvicdefects. The investigators performed two pilot studies: oneinvolving cadaveric specimens, and the other involving clini-cal revisions. All patients had a preoperative computed tomo-graphic scan to quantify the defect volume. The mean volumeof the experimental defects was 6.7 cm3. The mean volume of

osteolysis in the patients was 34.5 cm3. The surgeons were suc-cessful in filling 89.3% of the small lesions in the cadavericmodel. However, they were successful in filling only 44.7% ofthe defect volume in the patients. No data were given with re-gard to the degree of healing of these lesions.

Surgeons have utilized one of several treatment optionsfor pelvic osteolysis around a well-fixed cup: (1) liner ex-change only, (2) liner exchange with bone-grafting of the le-sions, (3) cementation of a liner in cases of an incompetentlocking mechanism with or without bone-grafting, and (4)revision of the shell. Talmo et al. reviewed the results of 128cup reoperations that had been performed for the treatmentof osteolysis over a period of twelve years. All cups were of the

same design, which was known to have a suboptimal lockingmechanism but a high success rate for durable bone fixation.Fifty-two percent of the procedures involved liner exchangeinto the preexisting shell, 27% involved shell revision, and21% involved cementation of a new liner into the preexistingshell. The mean duration of follow-up was 5.1 years. In theliner-exchange-only group, 24% of the hips required reopera-tion, one-half because of liner dislodgment and one-half be-cause of progressive polyethylene wear and pelvic osteolysis.In the liner-cementation group, 29% required reoperation,two-thirds because of dislocation and one-third because ofshell loosening. In the shell-revision group, 15% required re-


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operation, one-half because of dislocation and one-half be-cause of infection. The authors recommended shell revision as

the optimal treatment of polyethylene wear and osteolysis forthis particular cup design.

Outcome of Revision Total Hip ArthroplastyRevision total hip arthroplasty is performed for a very widerange of failure mechanisms. This has posed difficulty in as-sessing the outcome of revision total hip arthroplasty. Davis etal.7 prospectively evaluated 126 patients with use of the SF-36and WOMAC outcome instruments before and after surgery.The investigators found that preoperative pain (p = 0.002)and medical comorbidities (p = 0.02) were the most signifi-cant predictors of a successful outcome. Patients with a lowerpreoperative status did worse after surgery. Time spent on apreoperative waiting list did not affect the outcome. Compli-

cations occurred in 22% of the patients and did affect postop-erative pain and function. One limitation of the study was thatthere was no assessment of the difference in the complexity ofthe revisions. Garbuz et al., in a retrospective study of 222patients who had undergone revision total hip arthroplasty,sought to identify factors that predicted quality-of-life out-comes at one and two years after surgery. There was significantimprovement after surgery as compared with baseline. Theimprovement leveled off at one year after surgery. Predictivefactors for improved outcome included a better preoperativeWOMAC function score, an age of between sixty and seventy

years, male gender, a lower Charnley class, and no prior revi-sions. The baseline WOMAC pain level was not correlated

with outcome. Interestingly, the operating surgeon was a sig-nificant predictor of activity level after revision. These dataalso validate that a suboptimal preoperative status can have anegative impact on the outcome.

Current Status of Minimal

Incision Total Hip Arthroplasty

Recent clinical data have provided conflicting evidence withregard to the efficacy and safety of minimal incision total hiparthroplasty. Some of the most recent studies have focused notspecifically on minimal incision total hip arthroplasty butrather on the impact of a different surgical exposure on thesoft tissues around the hip and on the clinical outcome with

regard to gait and muscle strength. Picado et al.8

specificallyevaluated the effect of the lateral approacvh (partial detachmentof the abductors) on Trendelenburg gait. The investigatorsstudied forty consecutive patients with sequential examina-tions and electromyographic studies that were performed pre-operatively and at four, eight, twelve, and twenty-four weeks.One-half of the patients had a Trendelenburg gait before sur-gery, and 25% still did at one year after surgery. Electromyo-graphic findings consistent with muscle and nerve injury werefound in 42.5% of the patients at four weeks. Three of the pa-tients still had some electromyographic changes at six months.There was no correlation between the electromyographic find-

ings and a clinical Trendelenburg gait. While the authors didnot provide data with regard to the functional outcome, it is

clear that a persistent Trendelenburg gait is common after to-tal hip arthroplasty involving the direct lateral approach.One of the clinical impacts of minimal incision total hip

arthroplasty has been the development of newer instrumenta-tion to facilitate surgery. Baad-Hansen et al.9 performed a ca-daver study in which conventional acetabular reamers werecompared with chamfered reamers designed for minimal in-cision total hip arthroplasty. The purpose was to compare theaccuracy of bone preparation with use of these reamers of dif-ferent geometries. The investigators used a three-dimensionaldigital scanning technique to determine the best-fit spherecreated by the various reamers. On the average, there was 0.1mm and 0.3 mm of deviation from a perfect fit for the mini-mal incision total hip arthroplasty and conventional reamers,

respectively. Another important finding was that the differ-ence between the labeled reamer size and the actual reamerdimension could vary as much as 3 mm. Further refinementof instrumentation is necessary in order to ensure more accu-rate bone preparation, and surgeons should try to identify anydifferences between the reamers and actual cup dimensionprior to surgery.

One potential complication of minimal incision totalhip arthroplasty is malpositioning of the components becauseof limited visualization. Rittmeister and Callitsis10 reviewed500 consecutive total hip arthroplasties that had been per-formed by multiple surgeons at one center. Four hundred ofthese procedures had been performed with use of conven-

tional surgical approaches, whereas 100 had been performedwith use of a minimal-incision technique without navigation.For all 500 procedures, 19.8% of the cups fell outside of thedesirable abduction angle range (35 to 55) and 11.2% felloutside of the desirable anteversion range (5 to 25). Therewas no difference between conventional and minimal inci-sion approaches. Most important, some surgeons consistentlyplaced the cups in positions outside of the range. Those stud-ies suggest that much more instrumentation work remains tobe done to help surgeons more consistently achieve desirableacetabular preparation and cup placement.

Some surgeons have reported accelerated recovery fol-lowing two-incision minimal incision total hip arthroplasty.

Pagnano et al. conducted gait analysis and muscle-strengthtesting in patients following minimal incision total hip arthro-plasty with use of either the two-incision approach or a mini-posterior approach. Ten patients were randomized to eachgroup. Both groups had similar demographic characteristics,preoperative hip scores, and functional status. Both groupshad marked improvement in gait velocity, stride length, andstep width at eight weeks. There was no difference in any ofthe gait or muscle-testing parameters between the groups.In the study by Meneghini and Pierson, sixteen patients(seventeen hips) were randomized to one of three surgical ap-proaches: two-incision, mini-posterior, and mini-anterolateral.


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The mean age of the patients was fifty-three years, and themean body mass index was 26 kg/m2. All patients received

comprehensive preoperative instruction with an expectationto be discharged on the day after surgery. All patients receivedidentical anesthesia, pain management, and physiotherapy.The patients were blinded with regard to the surgical ap-proach, as were the hospital nursing and therapy staff. Four-teen of the seventeen hips met physical therapy criteria fordischarge by the next morning. With these small numbers,surgical approach did not appear to have an effect on earlydischarge. Pagnano et al., in a prospective, randomized studyof seventy-two patients, compared the two-incision techniquewith a mini-posterior minimal incision approach. All proce-dures were performed by the same surgeon. Outcome mea-sures were focused on early functional recovery. The meanduration of discontinuation of narcotic medication was

shorter for the patients in the two-incision group. Discon-tinuation of walking aids and return to daily activities werefaster for the patients in the mini-posterior incision group.The authors found no evidence that the two-incision mini-mal incision total hip arthroplasty had any dramatic effecton early return of function. In another study, Sirianni et al.evaluated forty-eight patients with instrumented gait analysisfollowing three different surgical approaches: conventionalposterior, mini-posterior, and mini-lateral. For all patients,gait velocity increased 10% at six weeks from the preoperativevalue. At six weeks, there was no difference among the groupswith regard to velocity, cadence, stride length, or single-limb-support time. The authors concluded that (1) the patients re-

covered to near-normal gait parameters by six weeks and (2)the surgical approach did not influence recovery.

NavigationMany surgeons have advocated for navigation in total hip ar-throplasty with the advancement of software and more clinicalexperience over the past five years. Navigation may be espe-cially important in minimal incision total hip arthroplasty. Atthe present time, the most useful application of navigation intotal hip arthroplasty has been for acetabular reconstruction.Malik et al. validated the precision of an imageless computernavigation system with use of postoperative computed tomog-raphy scans to quantify cup position. They obtained three sets

of data: (1) surgeon perception at the time of surgery, (2)measurements from standardized radiographs, and (3) mea-surements from computed tomography scans. The precisionwith the use of navigation was 3.6 for inclination and 4.4 foranteversion. The precision measured against postoperativeradiographs was 9.1 for inclination and 3.9 for anteversion.The precision of the experienced surgeons perception was11.4 for inclination and 12.3 for anteversion. The surgeonsestimate was only within 12 of the real position, in contrastto within 4 when using navigation. Thirty percent of thecups were >5 off alignment even when inserted by the seniorsurgeon with use of contemporary alignment jigs. Long-term

clinical follow-up is necessary to determine if more preciseimplant placement will result in fewer complications, better

fixation durability, and less articulation wear. Another benefitof navigation may be in hip resurfacing. Perlick et al. prospec-tively evaluated the precision of implant position in a study offifty hip resurfacing arthroplasties performed with or withoutnavigation. The inclination and the axial alignment of thefemoral resurfacing component were measured by two inde-pendent observers and were compared with the navigationvalues. The mean deviation from the ideal placement in theaxial plane was 2.9, compared with 4.8 when the conven-tional surgical technique was used. Navigation added onlyseven minutes to the surgery time. The authors concludedthat navigation may help to reduce the risk of notching, par-ticularly for less experienced surgeons while performing hipresurfacing.

Hip Resurfacing

Hip resurfacing has received much attention in the past yearsince the approval of the first implant system by the UnitedStates Food and Drug Administration. It is the fastest growing

joint arthroplasty procedure worldwide. Surgeon advocates,patient information sites, and the device companies all haveproposed that hip resurfacing is associated with superior func-tion and faster recovery as compared with conventional totalhip arthroplasty. Fowble, dela Rosa, and Schmalzried ques-tioned if the observed clinical outcome of hip resurfacing wasa function of patient selection and expectation rather than theprocedure itself. The investigators evaluated two groups of

patients: (1) fifty patients managed with hip resurfacing pro-cedures, and (2) thirty-five patients managed with totalhip arthroplasty procedures performed with use of a large-diameter head. These patients were prospectively followedfor two to four years. There were demographic differencesbetween the groups, with the patients in the hip resurfacinggroup being more frequently male (62%), being younger (bynine years), being less obese (lower body mass index), andhaving a lower anesthesia risk than those in the total hip ar-throplasty group. Patients in the hip resurfacing group alsohad a lower Harris hip score, more pain, a higher activityscore, and better range of motion before surgery. The operat-ing time was 18% longer in the hip resurfacing group, but that

group had less blood loss and fewer transfusions. There wasno difference between the groups with regard to the Harris hipscore after surgery. Patients in the hip resurfacing group hadhigher Short Form-12 physical, function, and activity scores.However, they also had a higher prevalence of mild pain.There was no difference between the groups with regard to thepostoperative range of motion. There was one dislocation ineach group. The preoperative differences between the groups,rather than the procedure itself, may have contributed to someof the observed differences after surgery.

A study involving three-dimensional simulation dem-onstrated that the flexion-extension arc following resurfacing


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was significantly less than that in the native hip and that fol-lowing conventional total hip arthroplasty. The large neck-to-

head ratio and the presence of a large prosthetic posterioracetabular wall with resurfacing were postulated to accountfor these findings.

Femoral neck fracture is the most important complica-tion following hip resurfacing. Most surgeons identify notch-ing of the femoral neck as the most important factor leadingto fracture. The other controversy is whether the femoralcomponent should be placed in neutral or in a valgus posi-tion. Masri et al. tested ten paired fresh-frozen cadaver speci-mens. On one side the femoral component was placed inneutral, and on the other side it was placed in 10 of valgus.A standardized notch (3 mm wide and 2 mm deep) was cre-ated in the superolateral aspect of the femoral neck. The in-vestigators also determined the bone mineral density of each

specimen. All specimens were loaded to fracture. There weretwo fracture patterns: (1) simple fracture (noted in fourteenspecimens [70%], with eight in neutral and six in valgus) and(2) crush fracture (noted in six specimens [30%], with two inneutral and four in valgus). The crush pattern reflected failurein compression in specimens with low bone mineral density.For those that failed in a simple fracture pattern, valgus place-ment increased the load to fracture by 30% over neutral place-ment, but component placement did not have an impact onfracture load in specimens with a low bone mineral density.These results suggest that placement of the femoral compo-nent in 10 of valgus in patients with normal-to-high bonemineral density can provide substantial protection against

femoral neck fracture following notching when comparedwith neutral placement. Davis et al. conducted a similar ca-daver experiment without notching of the neck. Placement ofthe femoral component in 10 of varus was associated with a12% reduction in ultimate fracture strength, whereas place-ment of the femoral component in 20 of valgus was associ-ated with a 32% increase in fracture strength. The results ofthese studies should help to define optimal patient selectioncriteria and surgical technique in order to minimize fracturefollowing hip resurfacing. Another potential factor related tofractures and femoral fixation failure is compromised femoralhead vascularity. In the study by Beaule et al.11, ten patientsundergoing surgery were evaluated with use of laser Doppler

flowmeter recordings during femoral head reaming. Therewas a mean 70% decrease in blood flow from baseline duringreaming. The authors recommended keeping the reamer asclose to the inferomedial neck as possible in order to minimizedamage to the retinacular vessels.

Hip resurfacing may be especially difficult in patientswith femoral head deformity. Boyd et al. reported the resultsof hip resurfacing in a study of eighteen hips with deformityresulting from Legg-Calv-Perthes disease. After a mean du-ration of follow-up of 4.2 years, 95% had a good to excellentHarris hip score. No fractures or loosening were reported.The authors recommended careful removal of marginal os-

teophytes around the neck to minimize impingement.Obesity poses another controversy in patient selection.

Amstutz and Le Duff presented the results of 148 hip resur-facing procedures that were performed in 138 patients with abody mass index of >30 kg/m2. The mean age was 49.4 years,and the mean body mass index was 33.4 kg/m2. There were nocases of acetabular or femoral component loosening. Two hipswere revised, one because of a femoral neck fracture and theother for cup placement. In a smaller subset of patients with abody mass index of >35 kg/m2, there were no cases of fractureor implant loosening.

With respect to patient age, Amstutz et al. followed 295hip resurfacing arthroplasties in patients who were youngerthan fifty years old. The mean age was 41.2 years. The meanduration of follow-up was 6.4 years. No cup revision wasdone. Ten hips required femoral revision because of loosen-

ing. Another hip was revised because of a femoral neck frac-ture. Radiolucent lines were observed in another eight hips.The five-year survival rate was 97.8% in patients with goodbone stock and proper surgical preparation. Hashmi andHolland reported on a prospective study of 107 consecutiveBirmingham hip resurfacing procedures after a mean durationof follow-up of 6.5 years. The mean age was 52.2 years for theseventy-four male patients and 47.8 years for the twenty-sixfemale patients. Two revisions were done because of femoralneck fracture. All surviving hips were rated as excellent. Thatstudy, which represented one of the first series of Birminghamhip resurfacing procedures performed by surgeons other thanthe designers, demonstrated the efficacy of hip resurfacing in

properly selected patients.

Complications

DislocationInstability remains among the most frequent causes of reoper-ation following total hip arthroplasty, and it is especially fre-quent following revision total hip arthroplasty. Ries and Kungreviewed the effect of head size in a study of 218 revision totalhip arthroplasties. There were four groups. Group 1 includedhips with an intact abductor mechanism and a 28-mm head,Group 2 included hips with an absent abductor mechanismand a 28-mm head, Group 3 included hips with an intact ab-ductor mechanism and a 36-mm head, and Group 4 included

hips with an absent abductor mechanism and a 36-mm head.The dislocation rates were 11.7%, 38%, 0%, and 38%, respec-tively, for the four groups. There was significant difference be-tween Groups 1 and 2 and between Groups 3 and 4. Thus, theintegrity of the abductor mechanism had a greater impact onthe dislocation rate than did the head diameter. Constrainedliners have been used to address instability in patients withan incompetent abductor mechanism. Guyen et al. reviewedforty-three failed constrained liners of a single design (tripolartype). These failures represented 11% of the 390 total hip ar-throplasties performed with use of this liner design. The meantime to failure was twenty-eight months (range, one to seventy-


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eight months). Most of the failures occurred in hips that hadhad multiple previous revision procedures, and the most com-

mon mechanism of failure was infection (28%). Among thedifferent mechanical failure mechanisms, the most commonwere fixation failure between shell and bone (26%), disloca-tion of the bipolar component (21%), and failure of the lock-ing mechanism between the liner and the shell (14%). Theauthors suggested judicious use of tripolar constrained linersin salvage situations.

InfectionA new and improved polymerase chain reaction (PCR) devel-oped at the Cleveland Clinic holds great promise in helpingwith the diagnosis of periprosthetic infection. A specific poly-merase chain reaction to detect Staphylococcus aureus (Staph-PCR) and another universal one to detect other organisms

(Univ-PCR) have been developed and have been shown tohave a sensitivity and specificity of 90% and 87.8%, respec-tively. Interestingly, the same study demonstrated that 12%of aseptic loosening cases showed presence of bacterialcolonization.

Currently, there is no consensus regarding the principlesof empiric antibiotic treatment of suspected infection. Fulker-son et al.12 conducted a retrospective review of positive cul-tures of specimens that had been obtained from the sites of110 total hip arthroplasties and eighty-four total knee arthro-plasties over thirteen years at a tertiary joint arthroplasty cen-ter. Seventy percent of the infections were classified as chronic;17%, as acute postoperative; and 13%, as acute hematoge-

nous. Gram-positive organisms were isolated in 84% of thecases. Staphylococcus aureus was the most common organismisolated from the site of total hip arthroplasty (45%), andStaphylococcus epidermidis was the most common organismisolated from the site of total knee arthroplasty (40%).Ninety-six percent of all organisms were sensitive to vanco-mycin; 88%, to gentamycin; and only 61%, to cefazolin. Cul-tures were positive for multiple organisms in 9.3% of thecases. Resistant organisms were most commonly found inspecimens from patients who had had a failure of previoustreatment and those from patients who had an acute postop-erative infection. The investigators recommended the use ofempirical antibiotic therapy. Specifically, they recommended

(1) that chronic infection should be treated with vancomycin,(2) that acute hematogenous infection should be treated withgentamycin and cefazolin, and (3) that infections involvingmultiple organisms should be treated with vancomycin and athird or fourth-generation cephalosporin. Last, they recom-mended that, if cultures were negative after four days, empirictherapy should be discontinued.

VenousThromboembolismDeep-vein thrombosis and pulmonary embolism are amongthe most common complications. Controversies principallycenter on the difference between deep-vein thrombosis rates

from screening with use of venography and the rates of actualsymptomatic events. Many surgeons believe that the efficacy

of a particular prophylaxis protocol should be determined bya reduction in symptomatic events rather than by the rates asdocumented with venography. Moreover, many surgeons haveutilized a multimodal prophylaxis protocol that has demon-strated excellent clinical efficacy13,14. However, multimodalprotocols are not sanctioned by the American College of ChestPhysicians (ACCP) guidelines, and these protocols are notconsidered to be in compliance with the measures mandatedby Medicare and other organizations.

Lachiewicz and Soileau14 prospectively evaluated 936patients managed with 1032 primary and revision total hiparthroplasties, 95% of which were performed with use of re-gional anesthesia. Prophylaxis against deep-vein thrombosisincluded the use of a thigh-high sequential compression de-

vice while the patient was in the use of aspirin (325 mg, ad-ministered twice daily for six weeks). Screening duplex ultra-sonography was performed an average of four days aftersurgery. Deep-vein thrombosis was documented in forty-onepatients (thirty-five of whom were asymptomatic), symptom-atic pulmonary embolism occurred in seven patients, and fatalpulmonary embolism occurred in only one patient. In that co-hort, the overall thirty-day mortality rate from all causes was0.3%. Keeney et al.13 evaluated the efficacy and safety of usinga multimodal prophylaxis protocol that included seven days ofadjusted-dose warfarin, mechanical prophylaxis, and acceler-ated mobilization. Screening was done by means of bilateralultrasonography on Day 3 or 4. Seven hundred and five pa-

tients undergoing primary or revision total hip arthroplastywere included. An asymptomatic deep-vein thrombosis wasdocumented in twenty-five patients (3.5%), and two-thirds ofthese clots were proximal. An additional five patients (0.7%)were managed for symptomatic deep-vein thrombosis. Symp-tomatic pulmonary embolism occurred in one patient. Therewere no deaths, readmissions, or late symptomatic deep-veinthromboses or pulmonary emboli. The authors found that aprior deep-vein thrombosis or pulmonary embolism, in-creased age, and male gender were significant risk factorsfor the development of deep-vein thrombosis or pulmonaryembolism within ninety days after total hip arthroplasty.

One current controversy is the duration of prophylaxis.

Dhupar et al.15

evaluated 2364 patients who were managedwith primary total hip arthroplasty and total knee arthro-plasty from 1994 to 2001 with use of duplex ultrasonographyas screening protocol. All patients received thromboembolicprophylaxis with use of adjusted-dose warfarin. Forty percentunderwent screening at the time of hospital discharge, and theothers underwent screening at two weeks after surgery. Therate of proximal deep-vein thrombosis in the thigh was notdifferent between the groups (2.5% and 2.2%, respectively).As a result of that study, the authors no longer perform rou-tine screening for asymptomatic patients.

Some orthopaedic surgeons have questioned whether


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the ACCP guidelines are safe, especially with regard to periop-erative morbidity. Burnett et al.16 conducted a prospective,

nonrandomized study of 129 consecutive total hip arthroplas-ties that were performed over six months at a single institu-tion. All patients received low-molecular-weight heparin (30mg, administered every twelve hours for ten days). The resultswere compared with those from the previous study involvingshort-term adjusted-dose warfarin from the same institution.The prevalence of major complications was 9% in the low-molecular-weight heparin group and 2.1% in the warfaringroup (p < 0.001). The prevalence of symptomatic deep-veinthrombosis was significantly higher in the low-molecular-weight heparin group (7% compared with 1.6%; p < 0.001).

As many patients travel long distances to undergo sur-gery, extended travel shortly after total hip arthroplasty is ofconcern, particularly because of the risk of venous throm-

boembolism. Ball et al. followed 502 patients who had amean age of fifty-one years. All patients received either low-molecular-weight heparin or adjusted-dose warfarin as pro-phylaxis. The patients traveled an average of 1319 miles(2123 km) (range, 200 to 8000 miles [322 to 12,875 km]) at amean of 6.5 days after surgery, 74% by airplane and 26% byautomobile. No deaths or pulmonary emboli were recorded.Symptomatic deep-vein thrombosis was identified in threepatients. Of interest, none of the 104 patients who had totravel continuously for a minimum of six hours had develop-ment of deep-vein thrombosis. The authors concluded thatthere was minimal risk of deep-vein thrombosis during travelwithin the first six weeks after total hip arthroplasty for pa-

tients receiving prophylaxis.

PeriprostheticFracturesThe success of treatment of periprosthetic femoral fractureshas improved with newer fixation devices and surgical tech-niques. OToole et al.17 reported on twenty-four fractures thatwere treated with a locking plate through a limited-incisionapproach at two tertiary trauma centers over a two-year pe-riod. Ten fractures occurred around the site of a total hip ar-throplasty, nine occurred around the site of a total kneearthroplasty, and five occurred around the sites of both pro-cedures. While fracture union was achieved in 95% of the pa-tients, radiographic analysis demonstrated malalignment of

>5 in 33% and shortening in 16%. Functional outcome wasgood to excellent for only 71% of the patients, and 70% of thepatients believed that their walking ability was worse than ithad been before the fracture. The use of a limited-incisiontechnique and a locking plate can result in fracture union witha low complication rate; however, this injury can remain func-tionally debilitating to the patients despite successful treat-ment of the fracture.

Intraoperative acetabular fracture is a rare complica-tion of total hip arthroplasty. Haidukewych et al.18 reportedtwenty-one such fractures in a joint registry of 7121 total hiparthroplasties that had been performed over eleven years at a

tertiary joint replacement center. No fractures occurred in as-sociation with cups that had been inserted with cement. The

fracture rate associated with cementless cups was 0.4%. Allfractures united without cup loosening. The investigatorsfound a greater risk of acetabular fracture in association withelliptical monoblock shells than in association with eitherelliptical modular or hemispherical modular designs. Thatreport raises concern with regard to preparation and cup in-sertion with use of minimal incision total hip arthroplastytechniques as well as with regard to the potential for fracturesduring resurfacing arthroplasty as many resurfacing cups havean elliptical monoblock geometry.

Bearing Surfaces

Metal-on-MetalMetal-on-metal articulations were initially introduced more

than four decades ago. The resurgence of this alternative bear-ing surface over the past decade was driven primarily by thehope to reduce wear and osteolysis. It has remained popularwith the current enthusiasm for hip resurfacing and large-head articulation total hip arthroplasties. In this update last

year, we cited several recent reports on the histological fea-tures of hypersensitivity in tissues retrieved from the sitesof total hip replacements with a metal-on-metal bearing.Korovessis et al.19 reported on the histological characteristicsof tissues retrieved from the sites of eleven total hip replace-ments with a metal-on-metal bearing. These hips were part ofa cohort of 194 total hip replacements with a contemporarytapered stem, a threaded cup, and a 28-mm metal-on-metal

articulation coupled with a polyethylene inlay design. Themetallurgy was a low-carbine, wrought cobalt-chromium-molybdenum alloy with a thickness of 3 mm. The investiga-tors consistently found histiocytes and giant cells with fineintracellular metallic debris. Moreover, a predominantlyperivascular lymphoplasmacytic infiltrate was observed. Theinvestigators found no correlation between the histologicalgrade and the presence of osteolysis on the radiographs. Inanother report, Milosev et al.20 followed 640 total hip arthro-plasties that had been performed with use of a similar metal-on-metal bearing design. The mean duration of follow-up wasseven years. Thirty-four hips were revised. Linear or expansilefemoral osteolysis was observed in 64% of the hips that were

revised because of aseptic loosening. Histological analysis ofretrieved tissue demonstrated perivascular lymphocyte andplasma cell infiltrates. Wear analysis of retrieved componentsdemonstrated that the mean total linear wear was 31 m, witha mean annual wear rate of 6.3 m/year. An abrasive wear pat-tern was consistently observed with electron microscopy onthe bearing surfaces of both the femoral head and the cup.Those two reports further documented hypersensitivity as apossible mechanism of failure following total hip arthroplas-ties performed with this metal-on-metal bearing, particularlywhen there is loosening.

Serum and urine metal ion levels in patients managed


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with metal-on-metal total hip arthroplasty have been reportedby investigators from several centers. MacDonald et al. re-

ported additional data in a prospective, randomized, blindedclinical trial of twenty-three patients with a metal-on-metalbearing and eighteen patients with a metal-on-polyethylenebearing. The bearings had identical designs. After a mean du-ration of follow-up of 7.2 years, the metal-on-metal groupcontinued to have elevated ion levels and the erythrocyte co-balt levels were eleven times elevated compared with those inthe metal-on-polyethylene group. Most importantly, therewas no decrease over time in the erythrocyte cobalt levels aftersix months following surgery. Moreover, compared with thevalues in the metal-on-polyethylene group, the urine cobaltlevels in the metal-on-metal group were thirty-nine times ele-vated (p < 0.001) and the chromium levels were twenty-eighttimes elevated (p < 0.001). These data may be specific to this

particular bearing coupling. Nonetheless, it is of concern thatthe levels continued to be elevated.

Ceramic-on-CeramicThis alternative hard-on-hard bearing coupling has been pop-ular over the past decade, but recently squeaking has beenreported as a clinical problem. This symptom, however, is notexclusive to ceramic-on-ceramic couplings. Jarrett et al. foundthat 7% of 159 ceramic-on-ceramic total hip arthroplastieswere associated with an audible squeak. However, as many as20% of patients reported some noise in the hips. The preva-lence of noise associated with metal-on-polyethylene total hiparthroplasties involving similar implant designs was 4%. Hips

with squeaking or noise were indistinguishable from silenthips with regard to clinical and radiographic findings. Kurtzet al. analyzed ten ceramic-on-ceramic bearings that were re-trieved, at a mean of 2.2 years, from patients who complainedof squeaking. There were four different designs from two dif-ferent manufacturers. Edge loading wear was observed in allten cups. Six of the ten patients also had evidence of impinge-ment of the stem neck against the cup. There were no chips orcracks in the ceramic bearing surfaces. Nishii et al. reviewed201 total hip replacements with a ceramic-on-ceramic bearingat a mean of seven years. Three hips were revised because ofliner fracture. Eight additional hips demonstrated notchingof the stem neck as a result of impingement. Noise was re-

ported in eight of these eleven hips with either fracture orstem notching. The cup inclination and anteversion angleswere also higher in these hips than in those without fractureor notching. Given currently available data, the etiology ofsqueaking of ceramic-on-ceramic couplings remains un-known but of concern.

PolyethyleneCross-linked polyethylene has become the most popular bear-ing surface for total hip arthroplasty. Optimization of thisbearing surface continues. With use of methods such as high-pressure crystallization, better cross-linking is being obtained

at lower doses of irradiation. Doping with antioxidants suchas trace elements of vitamin E also seems to confer benefits

to the cross-linked polyethylene. Salineros et al. analyzed re-trieved polyethylene liners produced by one manufacturerfor a single shell design with use of three different steriliza-tion techniques. Three groups were studied. The first groupincluded eleven 28-mm liners that had been sterilized withgamma radiation in air, which were evaluated after a mean offorty-nine months in situ. The second group included three28-mm liners that had been sterilized with gamma radiationin nitrogen, which were evaluated after a mean of thirty-threemonths in situ. The third group included three 28-mm andeight 32-mm highly cross-linked liners, which were evaluatedafter a mean of twenty-eight months in situ. The visual dam-age score for the highly cross-linked group was 50% less thanthose for the other two groups. Delamination as a mode of

failure was observed only in the gamma-in-air group. Mea-sured wear and creep were lowest in the highly cross-linkedgroup.

Larger-diameter femoral heads have the advantages ofmore clearance, greater range of motion, less impingement,and greater offset. However, polyethylene wear is of concern.Bragdon et al. evaluated penetration into highly cross-linkedpolyethylene liners in a study of thirty patients who were ran-domized to treatment with either a 28-mm head or a 36-mmhead; the implant design was identical in both groups. Themean duration of follow-up was three years. There was no sig-nificant difference between the groups following an initialbedding-in of 0.075 mm. Dorr et al. followed eighty-nine total

hip arthroplasties involving a single cup design. Each hip hadreceived the largest-possible diameter femoral head (28, 32,38, or 44 mm) to provide 5 mm of polyethylene thickness.There was no difference in clinical or radiographic outcomeamong the groups.

Although wear reduction is consistently documentedwith highly cross-linked polyethylene, the ability of thisbearing surface to minimize osteolysis continues to be stud-ied. Leung et al. evaluated seventy-six hips with computedtomography to detect and monitor pelvic osteolysis. Thecups were randomized to either conventional polyethylenesterilized in an inert environment or to highly cross-linkedpolyethylene. The mean duration of follow-up was 6.1 years.

Osteolysis was detected in 30% of the hips in the conven-tional group and 16.7% of those in the highly cross-linkedgroup, and the mean volume of the osteolysis lesion was sig-nificantly less in the highly cross-linked group (1.2 cm3 com-pared with 7.0 cm3; p = 0.001). Kitamura et al.21 examined aminimum of six serial radiographs for 145 hips that had un-dergone total hip arthroplasty with use of a cementless cup.The minimum duration of follow-up was ten years. The lin-ers were made of either conventional polyethylene or high-crystalline polyethylene. The femoral heads were 28 mm andwere made of either cobalt-chromium alloy or alumina ce-ramic. Pelvic osteolysis was present in 17.2% of the hips. The


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investigators determined the two-dimensional lesion sizeand the progression of the lesions over time. The mean rate

of lesion expansion was 42.7 49.0 mm

2

/year. The meantime to the first observation of a lesion was 5.7 years. How-ever, the mean x-intercept for the regression line was 1.3 3.0 years, indicating that the onset of osteolysis was muchearlier than was detectable on radiographs. There was a ten-dency for dome lesions to expand faster than peripheral le-sions, and more expansion occurred in men. No differencein osteolysis expansion was noted between the two types ofpolyethylene or the two head types. That study providedvaluable data that will be helpful for formulating practiceguidelines related to the frequency of radiographic follow-upfor patients managed with total hip arthroplasty, althoughthe osteolysis rate may vary between different polyethyleneliners and cup designs.

Bearing surface wear is affected by many factors. Somesurgeons have found greater polyethylene wear in cups withhigh inclination. Gallagher et al. analyzed wear in a study offorty-two cups of a single design and polyethylene type at aminimum of five years. The mean linear wear rate was 0.12mm/year, and the mean volumetric wear rate was 56 mm3/yr.There was a difference in linear wear between cups with aninclination of45 and those with an inclination of


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that involve acceleration and deceleration such as running,racquet sports, or basketball. One-third of the surgeons rec-

ommended returning to acceptable athletic activities at oneto three months after surgery. Ninety percent of the surgeonsagreed that patients could return to athletics by six months.However, the surgeon should discuss activity limitationswith each patient individually on the basis of experience andexpectations.

Future MeetingsThe major venues for scientific information exchange are theannual meetings of the American Association of Hip andKnee Surgeons (to be held in Grapevine, Texas, in November2007), the American Academy of Orthopaedic Surgeons (tobe held in San Francisco, California, in March 2008), andThe Hip Society (to be held in Pasadena, California, in Sep-tember 2007 and in San Francisco, California, in March2008). Instructional courses in complex primary and revi-sion total hip arthroplasties, including laboratory hands-ontraining, are sponsored by the American Academy of Ortho-paedic Surgeons at the Orthopaedic Learning Center.

Evidence-Based Orthopaedics

The editorial staff ofThe Journalreviewed a large number of

recently published research studies related to the musculoskel-etal system that received a Level of Evidence grade of I. Over100 medical journals were reviewed to identify these articles,which all have high-quality study design. In addition to arti-cles cited already in this Update, five level-I articles were iden-tified that were relevant to total hip arthroplasty. A list of thesetitles is appended to this review after the standard bibliogra-phy. We have provided a brief commentary about each of thearticles to help guide your further reading, in an evidence-based fashion, in this subspecialty area.

Michael H. Huo, MDNathan F. Gilbert, MDDepartment of Orthopedic Surgery, University of Texas SouthwesternMedical Center, 1801 Inwood Road, Dallas, TX 75390-8883. E-mail ad-dress for M.H. Huo: [email protected]

Javad Parvizi, MDRothman Institute at Thomas Jefferson University, 925 Chestnut Street,5th Floor, Philadelphia, PA 19107. E-mail address: [email protected]

References

1. Zhan C, Kaczmarek R, Loyo-Berrios N, Sangl J, Bright RA. Incidence and short-term outcomes of primary and revision hip replacement in the United States.J Bone Joint Surg Am. 2007;89:526-33.

2. Garbuz DS, Xu M, Duncan CP, Masri BA, Sobolev B. Delays worsen quality oflife outcome of primary total hip arthroplasty. Clin Orthop Relat Res. 2006;447:79-84.

3. Roder C, Staub LP, Eggli S, Dietrich D, Busato A, Muller U. Influence of preoper-ative functional status on outcome after total hip arthroplasty. J Bone Joint SurgAm. 2007;89:11-7.

4. Burke WV, Orishimo KF, McAuley JP, Engh CA. Midterm radiographic comparisonof cementless acetabular shells containing lateralized and nonlateralized liner. JArthroplasty. 2006;21:1099-104.

5. Garbuz DS, Toms A, Masri BA, Duncan CP. Improved outcome in femoral revi-sion arthroplasty with tapered fluted modular titanium stems. Clin Or thop RelatRes. 2006;453:199-202.

6. Weeden SH, Paprosky WG. Porous-ingrowth revision acetabular implants se-cured with peripheral screws. A minimum twelve-year follow-up. J Bone Joint SurgAm. 2006;88:1266-71.

7. Davis AM, Agnidis Z, Badley E, Kiss A, Waddell JP, Gross AE. Predictors offunctional outcome two years following revision hip ar throplasty. J Bone JointSurg Am. 2006;88:685-91.

8. Picado CH, Garcia FL, Margues W Jr. Damage to the superior gluteal nerveafter direct lateral approach to the hip. Clin Orthop Relat Res. 2007;455:209-11.

9. Baad-Hansen T, Kold S, Fledelius W, Nielsen PT, Soballe K. Comparison ofperformance of conventional and minimally invasive surgery acetabular ream-ers. Clin Orthop Relat Res. 2006;448:173-9.

10. Rittmeister M, Callitsis C. Factors influencing cup orientation in 500 con-secutive total hip replacements. Clin Orthop Relat Res. 2006;445:192-6.

11. Beaule PE, Campbell P, Shim P. Femoral head blood flow during hip resurfac-ing. Clin Orthop Relat Res. 2007;456:148-52.

12. Fulkerson E, Valle CJ, Wise B, Walsh M, Preston C, Di Cesare PE. Antibioticsusceptibility of bacterial infecting total joint arthroplasty sites. J Bone Joint SurgAm. 2006;88:1231-7.

13. Keeney JA, Clohisy JC, Curry MC, Maloney WJ. Efficacy of combined modality

prophylaxis including short-duration warfarin to prevent venous thromboembolismafter total hip arthroplasty. J Arthroplasty. 2006;21:469-75.

14. Lachiewicz PF, Soileau ES. Multimodal prophylaxis for THA with mechanicalcompression. Clin Orthop Relat Res. 2006;453:225-30.

15. Dhupar S, Iorio R, Healy WL, Dhimitri K. A comparison of discharge andtwo-week duplex ultrasound screening protocols for deep venous thrombosisdetection following primary total joint arthroplasty. J Bone Joint Surg Am.2006;88:2380-5.

16. Burnett RS, Clohisy JC, Wright RW, McDonald DJ, Shively RA, Givens SA,Barrack RL. Failure of the American College of Chest Physicians-1A protocol forlovenox in clinical outcomes for thromboembolic prophylaxis. J Arthroplasty.2007;22:317-24.

17. OToole RV, Gobezie R, Hwang R, Chandler AR, Smith RM, Estok DM2nd, Vrahas MS. Low complication rate of LISS for femur fractures adja-cent to stable hip or knee arthroplasty. Clin Orthop Relat Res. 2006;450:203-10.

18. Haidukewych GJ, Jacofsky DJ, Hanssen AD, Lewallen DG. Intraoperative frac-tures of the acetabulum during primary total hip arthroplasty. J Bone Joint SurgAm. 2006;88:1952-6.

19. Korovessis P, Petsinis G, Repanti M, Repantis T. Metallosis after contempo-rary metal-on-metal total hip ar throplasty. Five to nine-year follow-up. J Bone JointSurg Am. 2006;88:1183-91.

20. Milosev I, Trebse R, Kovac S, Cor A, Pisot V. Survivorship and retrieval analy-sis of Sikomet metal-on-metal total hip replacements at a mean of seven years.J Bone Joint Surg Am. 2006;88:1173-82.

21. Kitamura N, Sychterz-Terefenko CJ, Engh CA Sr. The temporal progressionof pelvic osteolysis after uncemented total hip arthroplasty. J Arthroplasty.2006;21:791-5.

22. Nuelle DG, Mann K. Minimal incision protocols for anesthesia, painmanagement, and physical therapy with standard incisions in hip andknee arthroplasties: the effect on early outcomes. J Arthroplasty. 2007;22:20-5.

23. Klein GR, Levine BR, Hozack WJ, Strauss EJ, DAntonio JA, Macaulay W,Di Cesare PE. Return to athletic activity after total hip arthroplasty. Consensusguidelines based on a survey of the Hip Society and American Association ofHip and Knee Surgeons. J Arthroplasty. 2007;22:171-5.


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Evidence-Based Articles

Related to Total Hip Arthroplastyvon Schewelov T, Sanzen L, Onsten I, Carlsson A, Besjakov J. Total hip re-placement with a zirconium oxide ceramic femoral head: a randomised roent-gen stereophotogrammetric study.J Bone Joint Surg Br. 2005;87:1631-5.

Four different articulation couplings in 114 total hip arthroplasties wereinvestigated. All arthroplasties were performed with use of an identical implantdesign with cement fixation. Wear and migration were measured with roentgenstereophotogrammetric analysis techniques at standard intervals of as long asfive years after surgery. Patients were randomized to treatment with (1) a stain-less steel head against standard polyethylene, (2) a stainless steel head againstextended-chain polyethylene, (3) a zirconium head against standard polyethyl-ene, or (4) a zirconium head against extended-chain polyethylene. The wearrates for the four groups were 0.11, 0.34, 0.17, and 0.40 mm/year, respectively(p < 0.008). There was no difference between the two types of heads againstextended-chain polyethylene (p = 0.26). There was no advantage associatedwith the use of a zirconium head. These data may be unique to the 22-mmhead diameter articulating against cemented cups. Conflicting wear charac-teristics of zirconium against polyethylene have been reported by other groups.

Johansson T, Engquist M, Pettersson LG, Lisander B. Blood loss after totalhip replacement: a prospective randomized study between wound compres-sion and drainage.J Arthroplasty. 2005;20:967-71.

A multicenter prospective, randomized study was undertaken to eval-uate the efficacy of wound compression after total hip arthroplasty. Fifty-onepatients were randomized to treatment with a wound compression girdle, andfifty-four patients served as controls. All procedures were performed with thepatient under normotensive spinal anesthesia. All implants were cemented.There was no difference between the groups in terms of total blood loss (p =0.13). However, the compression girdle group had fewer transfusions (p =0.05) and less bloody drainage from the incision (p = 0.04). There was no dif-ference between the groups in terms of the wound infection rate or the rate ofvenous thromboembolism. This part icular compression device may be usefulfor selected patients. However, no cost analysis was done.

Harse JD, Holman CD. Charlsons Index was a poor predictor of quality of lifeoutcomes in a study of patients following joint replacement surgery.J Clin Ep-idemiol. 2005;58:1142-9.

The Charlson index, a validated instrument that is used to assess theimpact of comorbidities on the outcome of medical interventions, was evalu-ated following 408 joint arthroplasties that had been performed in 392patients over twelve months at a single institution. Regression analysis dem-onstrated the Charlson index to be a poor predictor of health-related qualityof life. It was found to explain only 1.79% of the differences in the SF-36 phys-ical scores among patients. The Charlson index was an especially ineffectivemeasure for patients with relatively low levels of comorbidities. Alternative in-struments should be developed to provide a more valid assessment for smalldifferences in outcome following total joint arthroplasty.

Kwon MS, Kuskowski M, Mulhall KJ, Macaulay W, Brown TE, Saleh KJ. Doessurgical approach affect total hip arthroplasty dislocation rates? Clin OrthopRelat Res. 2006;447:34-8.

A meta-analysis was done to evaluate the efficacy of capsular repairfollowing the posterior approach with regard to the dislocation rate. A com-prehensive review produced only five acceptable studies that directly com-pared the dislocation rates between hips with and without soft-tissue repair.The dislocation rate was 0.49% for hips with the repair and 4.46% for thosewithout the repair. The relative risk of dislocation without capsular repairwas 8.21 times greater (95% confidence interval, 4.05 to 16.67). A separatesystematic review of eleven studies demonstrated no difference in the dislo-cation rates among anterolateral, direct lateral, and posterior approacheswith capsular repair (0.70%, 0.43%, and 1.01%, respectively). The study didnot specifically analyze the potential impact of prosthetic design and im-plant position.

Roderick P, Ferris G, Wilson K, Halls H, Jackson D, Collins R, Baigent C.Towards evidence-based guidelines for the prevention of venous thromboem-bolism: systematic reviews of mechanical methods, oral anticoagulation, dex-

tran and regional anaesthesia as thromboprophylaxis. Health Technol Assess.2005;9:iii-iv, ix-x, 1-78.

Prophylaxis against venous thromboembolic disease has received in-tense attention of late because of the initiation of the Surgical Care Improve-ment Program. This study was a comprehensive analysis of the efficacy ofdifferent types of prophylaxis against venous thromboembolic disease and theeffect of anesthesia in patients undergoing surgery. The investigators did notlimit the analysis to only orthopaedic procedures. They also did not includean analysis of low-molecular-weight heparin. Nonetheless, the study is an ex-cellent synopsis of a detailed analysis of some of the most popular prophylaxismethods used by orthopaedic surgeons. The authors found that mechanicaldevices reduced the rate of venous thromboembolic disease by two-thirds incomparison with the rate for controls, and the addition of pharmacologicalprophylaxis did not improve the efficacy. There was no difference amongstockings, intermittent compression, or foot pumps. These devices reducedthe risk of proximal deep-vein thrombosis by 66% and reduced the risk of

pulmonary embolism by 50%. Oral anticoagulants (principally warfarin) re-duced the risk for overall venous thromboembolism and proximal deep-veinthrombosis by 50%, and they reduced the risk of pulmonary embolism bynearly 80%. The statistical significance was unclear because of the low rate ofreporting in trials; thus, there was the possibility of selection bias. The use oforal anticoagulants did double the risk of major bleeding. Regional anesthesiahad a significant impact on the rate of venous thromboembolism in compari-son with general anesthesia, with the former being associated with a 50% re-duction. These are important data for the clinician to reference. This studyclearly underscores the multifactorial nature of venous thromboembolismand the complications of prophylaxis in the clinical setting. The major limita-tion of the study is that the investigators did not study the dif ference betweenoral anticoagulants and low-molecular-weight heparin.

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New Arthro Aug 2007