What's New in Total Hip Arthroplasty

Transcription

1 This is an enhance PDF from The Journal of Bone an Joint Surgery The PDF of the article you requeste follows this cover page. What's New in Total Hip Arthroplasty Michael H. Huo, Java Parvizi, B. Sonny Bal an Michael A. Mont J Bone Joint Surg Am. 2008;90: oi: /jbjs.h This information is current as of September 2, 2008 Reprints an Permissions Publisher Information Click here to orer reprints or request permission to use material from this article, or locate the article citation on jbjs.org an click on the [Reprints an Permissions] link. The Journal of Bone an Joint Surgery 20 Pickering Street, Neeham, MA

2 2043 COPYRIGHT Ó 2008 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED Specialty Upate By Michael H. Huo, MD, Java Parvizi, MD, B. Sonny Bal, MD, an Michael A. Mont, MD Total hip arthroplasty remains one of the most frequently performe reconstructive operations. Much work has again been one in this iscipline over the past year with regar to scientific investigation, clinical outcome assessment, an the treatment of complications. In aition, controversies relate to venous thromboembolism, meical-legal issues, an surgeon-inustry relationships have been at the center of scrutiny an meia coverage. We have electe to organize this upate into six sections: (1) outcome of primary total hip arthroplasty, incluing bearing surface options; (2) outcome of revision total hip arthroplasty, incluing new methos of enhancement of bone growth an fixation; (3) hip resurfacing arthroplasty; (4) minimal incision surgery; (5) complications; an (6) practice management, incluing meical-legal issues, workforce issues, an inustry-surgeon relationships. Outcome of Primary Total Hip Arthroplasty Femoral Stem Many surgeons have reporte excellent intermeiate to longterm results in association with the use of tapere stems inserte without cement uring primary total hip arthroplasty. Mallory reporte on 2000 consecutive arthroplasties that were performe between 1984 an The mean uration of follow-up was 5.5 years. The rate of femoral stem survival was 98.6% at five years, 98.6% at ten years, an 96.6% at fifteen years. A separate analysis with use of aseptic loosening as the en point emonstrate a survival rate of 99.5% at five an ten years an of 99.1% at fifteen years. This success was attribute to the stem geometry an surface texture. Aaptive bone changes after total hip arthroplasty vary accoring to biomaterials, esign geometry, an surface texture. Proximal bone stress transfer has been thought to be less in association with proximally coate stems as compare with Specialty Upate has been evelope in collaboration with the Council of Musculoskeletal Specialty Societies (COMSS) of the American Acaemy of Orthopaeic Surgeons. extensively coate stems. Capello et al. followe 144 hips that ha been treate with a stem that was proximally coate with hyroxyapatite. All stems were well fixe. Thirty-seven percent of the femora emonstrate stress-transfer bone remoeling at fifteen years. There was no correlation with preoperative bone ensity, bone geometry, stem size, boy weight, age, or iagnosis. These stress-transfer changes were more prevalent in women than in men (45% compare with 25%; p = 0.008). Hips with stress-transfer bone remoeling in general ha a smaller cortical ratio an a lower percentage of the canal fille by the stem istally. The clinical relevance of these changes is unclear. Component malpositioning, particularly varus, has been associate with higher failure rates. Min et al. 1 reviewe a consecutive series of ninety-eight arthroplasties that ha been performe with a cementless tapere-wege stem; the mean uration of follow-up was 7.7 years. The stem position was neutral in 63% of the hips, valgus in 21%, an varus in 16%. No revision was one. There was no ifference among the three groups in terms of the Harris hip score or the prevalence of thigh pain. Similar bone remoeling changes were observe in all patients, regarless of stem position. The authors conclue that varus position i not aversely affect fixation urability or clinical outcome. Acetabular Component Bone remoeling aroun cementless cups has not been extensively stuie. Meneghini et al. conucte a prospective ranomize stuy to quantify periacetabular bone ensity after primary total hip arthroplasty; the mean uration of follow-up was 7.5 years. Sixteen patients were ranomize into two groups of monobloc hemispherical cementless cups: nine patients receive a porous tantalum cup, an seven receive a cup with a titanium-alloy beae surface. Bone mineral ensity was measure aroun the cup as well as in the contralateral acetabulum, which serve as the control. There was a ramatic ifference between the two types of cups. Bone ensity e- Disclosure: The authors i not receive any outsie funing or grants in support of their research for or preparation of this work. Neither they nor a member of their immeiate families receive payments or other benefits or a commitment or agreement to provie such benefits from a commercial entity. No commercial entity pai or irecte, or agree to pay or irect, any benefits to any research fun, founation, ivision, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immeiate families, are affiliate or associate. J Bone Joint Surg Am. 2008;90: oi: /jbjs.h.00741

3 2044 crease aroun the titanium-alloy cups, whereas it increase aroun the tantalum cups. The ifference was especially pronounce in the region between 6 an 12 mm from the cup periphery an in the posterosuperior aspect of the acetabulum. The relative increase of bone ensity aroun the tantalum cups range from 5% to 40% in comparison with the contralateral acetabulum. These changes may not be reprouce with a moular tantalum cup because the ifferent esign features of a moular cup result in ifferences in the moulus of elasticity of the component. Ceramic-on-Ceramic Bearings Ceramic-on-ceramic bearings have been in clinical use for nearly forty years. Auible squeaking in a small number of patients with this bearing combination has receive much attention recently. Walter et al. 2 conucte a etaile raiographic analysis of component positioning in seventeen hips with squeaking. These hips represente 0.7% of the series of 2397 hip arthroplasties that were performe with use of a ceramic-on-ceramic bearing at their institution over an eightyear perio. The mean time interval to the onset of squeaking symptoms was fourteen months following the inex hip arthroplasty. There were a variety of implant esigns, with the vast majority of the bearing surfaces being manufacture by a single company (CeramTec, Plochingen, Germany). The raiographs an compute tomography scans of these hips were compare with those for a group of nonsqueaking hips that were matche accoring to clinical profile an implant esign. The cup position was foun to be outsie of the ieal range (anteversion in excess of 25 an abuction in excess of 45 )in 65% of the squeaking hips. In contrast, only 6% of the nonsqueaking hips ha an outlier cup position. In the revise hips, the investigators consistently foun evience of articulation amage ue to impingement or ege-loaing as a result of suboptimal component positioning. Lusty et al. 3 reviewe 301 consecutive primary total hip arthroplasties that ha been performe with use of a thir-generation ceramic-on-ceramic bearing coupling; the minimum uration of follow-up was five years (mean, 6.5 years). The rate of survival of both components with aseptic loosening as the en point was 99% at seven years. The most common complications were periprosthetic femoral fracture (prevalence, 1.7%) an psoas teninitis (prevalence, 1.3%). The authors reporte only one case of squeaking from the bearing (prevalence, 0.3%). The mean wear rate in the seven retrieve femoral heas was calculate to be 0.3 mm 3 per year. There was one case of pelvic osteolysis, which was attribute to impingement of the neck of the stem against the ege of the cup. The exact mechanism causing squeaking was not efine. In aition to ege impingement as escribe above, Sariali et al. formulate a threeimensional biomechanical an kinematic moel of the hip. Their moel emonstrate that microseparation coul be an important mechanism leaing to the generation of noise from these couplings. Fracture of the ceramic bearing remains the most feare complication. Koo et al. 4 followe 312 patients (367 hips) from four centers who ha unergone total hip arthroplasty with use of ientical implants with a ceramic-on-ceramic bearing. Five femoral hea fractures occurre (prevalence, 1.4%). All of these fractures occurre uring normal physical activities, an all occurre in hips with a short neck. The fractures involve a circular crack along the circumference of the thinnest portion of the hea, extening raially along the longituinal axis. This rate of component fracture may be specific to this particular esign. Highly Cross-Linke Polyethylene Bearings Highly cross-linke polyethylene has evolve into the most frequently use bearing material for total hip arthroplasty. Many stuies have ocumente clinically superior wear characteristics as compare with conventional polyethylene. Questions remain as to whether this bearing surface will be proven to be clinically more urable in patient populations that have been known to be especially at risk for wear. Stephani et al. reporte less femoral hea penetration in matche groups of obese patients when highly cross-linke polyethylene was compare with conventional polyethylene. The authors examine the results of forty-one hip arthroplasties after a mean uration of follow-up of 4.75 years. Highly cross-linke polyethylene was use in twenty-one hips (twelve in nonobese patients an nine in obese patients), an conventional polyethylene was use in twenty hips (sixteen in nonobese patients an four in obese patients). The linear penetration rate was significantly lower in the group with highly cross-linke polyethylene uring both the being-in phase (p = 0.036) an the steay-state phase (p = 0.009). The mechanical properties of polyethylene are altere uring the cross-linking process. Reuction of material strength an toughness may result in fracture. Tower et al. 5 reporte the results of a etaile analysis of four retrieve fracture cup liners that ha been mae of highly cross-linke polyethylene by a single manufacturer. Cross-linking ha been one by means of 10-Mra electron-beam irraiation with subsequent above-melt-temperature annealing. All four liners ha been inserte into an ientical acetabular shell esign. All liner fractures occurre at the superior aspect, along the groove in the polyethylene that engages the locking ring of the shell. There was no evience of oxiation, an no other in vivo egraation was foun. Surface wear was present an was classifie as moerate in all four. When the liners were teste against never-implante control liners mae of the same material, there was no ifference in terms of the mechanical properties. The authors postulate that the fractures were ue to a combination of thin polyethylene in cups place with a high abuction angle, resulting in excessive loaing at the superior ege. Cross-linking with a below-melt-temperature annealing process is believe to improve the mechanical properties.

4 2045 Currier et al. 6 examine eleven retrieve liners mae of the same cross-linke polyethylene that was manufacture with use of below-melt-temperature annealing. The liners ha been in service for 0.1 to 5.3 years. Oxiation of the material was present in all liners, with a visible white ban being seen in seven of them. Six of these seven liners also exhibite clinical fatigue amage. Overall, eight of the eleven liners showe evience of impingement or islocation. The oxiation-relate reuction of mechanical properties in the polyethylene was sufficient to allow the fatigue amage seen in these liners. Aitional improvements in highly cross-linke polyethylene have been mae. Brunner et al. reporte aing the antioxiant agent vitamin E to the manufacturing process. This process has been emonstrate to improve the wear characteristics an the material oxiation level. Human articular cartilage is normally covere with a nanoscale phospholipi layer that contributes to lubricity an biocompatibility. Moro et al. use an ultraviolet-rayinuce polymerization technique to coat the polyethylene liner surface with a biocompatible phospholipi polymer, 2-methacryloyloxyethyl phosphorylcholine. The important finings were that (1) wear particle prouction was reuce following hip simulator testing an (2) wear particles inuce less bone resorption in an animal moel. Outcome of Revision Total Hip Arthroplasty Cementless fixation has become the preominant preference for revision hip arthroplasty. Callaghan et al. presente the twenty-year follow-up results of eighty-three consecutive hip revisions that were performe with use of contemporary cementing techniques. The mean age at the time of revision was 62.4 years. For all patients, the failure rate (incluing both re-revision an loosening) was 39.1% for the cups an 13.8% for the stems. Among the living patients, 48% of the cups an 13% of the stems were re-revise. These results shoul provie a founation for comparison with the results of newer technology an cementless fixation for revision hip arthroplasty. Acetabular Revision One of the most ifficult clinical ecisions is how to etermine the optimal timing of surgical intervention for the treatment of periprosthetic osteolysis in an asymptomatic patient. Howie et al. 7 reviewe sequential quantitative compute tomography scans of the pelvis in a stuy of thirty hips with a cementless moular cup; all of the cups were of an ientical esign. The initial scans were performe after a minimum of ten years of follow-up. The subsequent scans were performe at a meian of fifteen months (range, twelve to twenty-seven months) after the inex scan. Eighty-nine percent of the femoral heas were smaller than 28 mm. The mean outer iameter of the cup was 52 mm (range, 48 to 62 mm). Osteolysis progresse in sixteen (53%) of the thirty hips. Osteolytic lesions measuring >10 cm 3 in volume on the inex scan were 2.5 times more likely to progress. Patients with a greater linear wear rate, a higher activity level, Charnley class-a involvement, an a larger femoral hea size ha significantly larger lesions. Significant preictors for lesion progression were the initial size of the lesion, wear rate, an femoral hea size. There was, however, consierable variation in the rates of progression of pelvic osteolysis in this cohort of patients with stable cementless cups. Revision because of liner wear an osteolysis is common. Paprosky an Sporer reporte on 127 acetabular revisions that were intene for liner exchange only. The authors foun malpositioning in 19% of the hips, a cup esign that was not suitable for liner exchange (because it was too small or ha a ifferent geometry) in 15%, an unstable fixation in 6.2%. Forty percent of the cups initially assesse to be without nee for shell revision actually require full cup revision at the time of surgery. Hozack et al. reviewe the results of forty-three acetabular revisions. Twenty-nine hips ha a liner exchange only, whereas fourteen hips ha full cup revision. The mean age of the patients was sixty-three years. Six (21%) of the twenty-nine hips that ha only liner exchange require rerevision because of shell loosening at a mean of twentytwo months (range, three to fifty-three months). Only one (7%) of the cups in the full revision group faile because of loosening at a comparable follow-up interval. The numbers were too small to conclue whether full cup revision shoul be consiere when the preoperative planning is for only liner exchange for the treatment of polyethylene wear an osteolysis. Large segmental or combine acetabular bone eficiency poses a substantial challenge. No single surgical technique has been prove to be the most efficacious an urable. Abeyta et al. 8 reporte the long-term results of fifteen revisions that ha been performe with use of an oblong-shape cup inserte without cement; the mean uration of follow-up was eleven years. Three hips require re-revision. The mean Harris hip score for the remaining twelve hips was 76.5 at the time of the latest follow-up. Palm et al. 9 reporte on the use of allograft impaction an cementless cups with a hyroxyapatite coating for acetabular revision in a stuy of eighty-seven patients with large bone efects. Containe efects were present in 45% of the patients, segmental efects were present in 49%, an combine or uncontaine efects were present in 6%. The mean uration of follow-up was nine years. The rate of cup survival was 94% at nine years, with aseptic loosening as the en point. The hyroxyapatite coating along with supplemental screw fixation (both ome an peripheral) may have contribute to the success of these revisions even in the absence of sufficient contact with the host bone. Another surgical technique to aress acetabular bone eficiency is the use of moular tantalum augments. Garbuz et al. followe thirtyfour revisions performe with use of tantalum augments an tantalum cups for a mean of thirty-four months. Two cups faile an require re-revision, an short-term success was seen after 91% of the revisions.

5 2046 Femoral Revision An extensively coate stem has been successful for femoral revision surgery. Hamilton et al. 10 reporte on the use of such a stem esign for the revision of a faile extensively coate stem. Sixteen failures were ientifie in a large atabase of 711 femoral revisions that ha been performe with use of a single stem esign with an extensive porous coating. All sixteen faile stems were re-revise with use of the same stem esign. Three of the sixteen stems ha insufficient follow-up. The mean uration of follow-up was 9.8 years for the remaining thirteen stems. None of those thirteen stems were re-revise. Bone integration was evient in twelve of the thirteen stems raiographically. Technical challenges may be formiable in the presence of severe femoral bone eficiency. Parvizi et al. 11 reporte on the use of a moular proximal femoral replacement prosthesis for forty-eight complex femoral revisions. The inications for revision inclue periprosthetic fracture (twenty patients), reimplantation because of a eep infection (thirteen), a faile arthroplasty (thirteen), nonunion of an intertrochanteric fracture (one), an raiation-inuce osteonecrosis (one). The mean uration of follow-up was three years. There was significant improvement in the mean Harris hip score, from 37 preoperatively to 65 postoperatively. However, only twentytwo of the hips were rate as goo or excellent at the time of the latest follow-up. Ten patients require a total of eighteen reoperations. The survival rate with revision as the en point was 87% at one year an 73% at five years. While this may be an effective option for complex cases with severe bone eficiency, the functional outcome an the urability of the implant are less optimal than those associate with a typical revision. Improvement in Implant Fixation an Bone Growth Bone loss an suboptimal implant fixation to eficient bone remain the principal challenges to a successful clinical outcome. Several groups have reporte using pharmacological agents to retain or to increase bone mass following total hip arthroplasty. Iwaki et al. reporte an increase in bone mass following the aministration of riseronate (a bisphosphonate) in a prospective ranomize clinical trial with controls at the time of the two-year follow-up. Eberhart et al. reporte enhance osseointegration of hyroxyapatite-coate implants in association with bisphosphonate aministration in a rat moel. Even more important, they foun an equal amount of osseointegration in osteoporotic bone. Another group from Hanover, Germany, reporte positive bone remoeling an retention of bone mass in association with local aministration of magnesium hyroxie aroun the bone-implant interface in patients with osteoporosis. Several types of titanium foam metal have been introuce into clinical application over the past two years. These materials generally have a larger pore structure that promotes greater bone ingrowth as compare with stanar beae or plasma-spraye titanium surfaces. Garbuz et al. 12 reporte on cylinrical porous tantalum implants that were inserte into the istal part of the femur of eighteen rabbits. Three types of implants were inserte: (1) uncoate tantalum implants (control), (2) tantalum implants coate with calcium phosphate, an (3) tantalum implants coate with both calcium phosphate an alenronate. The authors reporte significantly more total gap filling (143%), bone ingrowth (259%), an total bone formation (193%) in association with the cyliners that were coate with both calcium phosphate an alenronate in comparison with the uncoate implants. All of the values were also significantly greater when the implants coate with calcium phosphate plus aitional alenronate were compare with those coate with calcium phosphate alone. If this type of coating enhancement can be prove to be effective an safe in the clinical setting, the outcome of complex revisions with bone eficiency may be improve. This type of material also may enhance soft-tissue attachment. Dickey et al. foun that the most ieal material characteristics for the strongest soft-tissue ingrowth were (1) a pore size ranging from 500 to 600 mm an (2) 30% ranomness. Further evelopment of this type of material may ai in the reattachment of the hip abuctors as well as the extensor mechanism aroun the knee joint. Gene therapy has been applie to total hip arthroplasty. DePoorter et al. reporte on the use of gene therapy an the injection of aitional cement into the bone-implant interface aroun loose femoral stems. The investigators use a viral vector, HAV-5ntr, to eliminate the interface fibrous tissue. They then combine it with the prorug CB1954 an injecte a combination of the vector an the prorug into the interface in twelve patients with a loose stem. The vector was injecte into the hip joint irectly, followe by prorug injection in two ays an by cement injection five to seven ays later. The patients reporte a reuction in pain an an improvement in overall function in the short term. Bone remoeling aroun the bone-implant interface an stem fixation stability remain to be further evaluate. Such an approach may become useful for elerly patients with substantial meical comorbiities who are not suitable caniates for major revision surgery. Hip Resurfacing Arthroplasty Hip resurfacing continue to receive much attention in the past year with the approval of a secon implant system in the Unite States. Moreover, there has been intense meia coverage as well as frequent postings on patient an inustry web sites. At the present time, it is estimate that hip resurfacing accounts for as many as 6% to 9% of all total hip arthroplasties in some countries, incluing Australia (7.9%), France (6%), Germany (9%), an the Unite Kingom (7%). The current enthusiasm for hip resurfacing may have le to inaccurate an inappropriate patient expectations. Murphy et al. conucte a prospective stuy at a tertiary joint arthroplasty center. One hunre an thirty-nine consecutive patients were surveye,

6 2047 an 41% were aware of hip resurfacing. Among these, 46% learne of the proceure through the Internet an 42% learne of the proceure from family an friens. Only 19% reporte having receive information from an orthopaeic surgeon. Eighty-two percent believe that hip resurfacing was safer than a stanar total hip arthroplasty, an 80% believe that hip resurfacing involve less soft-tissue amage an a faster return to function. When aske which type of hip arthroplasty woul be preferable, 54% of the responents preferre hip resurfacing, only 8% preferre a stanar total hip arthroplasty, an 38% were unsure. There is clearly a iscrepancy between patient perception an the scientific literature with regar to the clinical efficacy an safety of hip resurfacing arthroplasty. Avocates for hip resurfacing have propose that this proceure is associate with a superior functional outcome in comparison with stanar total hip arthroplasty. Lavigne et al. conucte a ranomize, prospective stuy in which hip resurfacing (107 patients) was compare with total hip arthroplasty (103 patients); both proceures were performe with use of ientical surgical techniques. The uration of follow-up range from two to five years. Patients from both groups reporte a high level of satisfaction, with no ifference between the groups in terms of functional outcome measures or complications. The authors also reporte higher activity levels in another cohort of patients who unerwent hip resurfacing. Haa et al. reporte superior functional outcome in a matche-pair analysis of forty patients, each of whom ha unergone hip resurfacing or total hip arthroplasty. Mont et al., in a matche-pair comparative analysis that inclue fifty-four patients in each group, reporte higher postoperative activity levels among patients who ha been manage with hip resurfacing. Naal et al. surveye 112 patients at twenty-four months following hip resurfacing. Approximately 26% of the patients performe sports four times or more per week for longer than sixty minutes per session. One of the limitations of all of these stuies was a higher preoperative activity level in the hip resurfacing cohort. This represente a selection bias that coul have resulte in the higher activity level at the time of the latest follow-up. In summary, ifferences in patient selection make meaningful comparisons of postoperative activity quantification ifficult between hip resurfacing an stanar total hip arthroplasty. Le Duff et al. 13 specifically analyze the activity levels of obese patients who ha unergone hip resurfacing. In that stuy, 125 patients (144 hips) who ha a boy mass inex of >30 kg/m 2 were compare with 531 patients (626 hips) who ha a lower boy mass inex. The University of California at Los Angeles (UCLA) function an activity scores were lower in the obese group. The non-obese group ha higher physical component scores on the Short Form-12 (SF-12) an higher Harris hip scores. The five-year implant survival rate was significantly higher in the obese group (98.6% compare with 93.6%), an the femoral component size was significantly larger in the obese group. The authors conclue that the better implant survival was attribute to lower activity level an larger implant size in the obese group. Gait analysis has been performe to compare hip resurfacing an stanar total hip arthroplasty. Shimmin et al. foun no ifferences in the gait characteristics between the hip resurfacing group (fourteen hips) an the total hip arthroplasty group (twelve hips). Moreover, both of these groups were no ifferent from a thir (control) group mae up of agematche patients without any hip isease. Lavigne et al. reporte gait ata for three istinct groups of eight patients each; the first group was manage with hip resurfacing, the secon group was manage with stanar total hip arthroplasty, an the thir group was manage with hip arthroplasty with use of a large-iameter femoral hea. The investigators foun better gait measurements in the hip resurfacing an large-iameterhea groups than in the stanar total hip arthroplasty group. There was no ifference between the hip resurfacing an the large-iameter-hea groups. There is controversy with regar to which surgical approach is best for hip resurfacing with regar to exposure, implant position, an preservation of femoral hea vascularity. In the stuy by McBrye et al. 14, 135 hip resurfacings that ha been performe through the irect lateral approach were compare with another 774 hip resurfacings that ha been performe through the posterolateral approach. After intermeiate-term follow-up (range, two to ten years), there were no ifferences between the two approaches with regar to complications, the rate of reoperation, implant survival, or hip scores. The eight-year implant survival rate exceee 97% for both approaches. Steffen et al. 15 ocumente less reuction of femoral hea bloo flow in association with the anterior approach in contrast to the posterolateral approach. Kahn et al. also ocumente less reuction of bloo flow in association with the anterolateral approach in contrast to the posterolateral approach. In summary, the posterolateral approach oes lea to greater reuction of femoral hea bloo flow. However, there are no ocumente ifferences in terms of clinical outcome, the urability of fixation, or complications when these ifferent surgical approaches are compare. Longer-term follow-up is necessary to etermine if there is any ifference in implant survival as a function of the surgical approach use for hip resurfacing arthroplasty. More clinical outcome ata from a large series of hip resurfacing proceures performe at ifferent centers were reporte at the 2008 Annual Meeting of the American Acaemy of Orthopaeic Surgeons. The secon implant system that was approve by the Unite States Foo an Drug Aministration in 2007 was the Cormet esign (Stryker, Mahwah, New Jersey). Three hunre an thirty-seven hips were inclue in a Unite States trial with a minimum uration of follow-up of two years. The Cormet system was associate with an overall revision rate of 4.7% (compare with 1.1% for stanar total hip arthroplasty) an a femoral neck fracture rate of 3.3%. In another stuy reviewing the experience of a single surgeon

7 2048 with 2474 hip resurfacings, the overall failure rate was 3.8% after a mean uration of follow-up of seven years. The femoral neck fracture rate was only 0.6%. Of the forty-eight hips that were revise, twenty-nine ha substantial femoral osteolysis. In the largest single-surgeon clinical series of >4000 hips, the nineyear rate of implant survival was 98%. Higher failure rates were observe in women, patients who ha ha previous surgery, an patients with osteonecrosis. Of the forty-one revisions, eighteen were performe because of a femoral neck fracture. The Australian hip resurfacing registry inclues >10,000 hips that have been treate since The five-year revision rate was 3.8% overall, compare with 2.8% for stanar total hip arthroplasty. The revision rate was 1.9% for men uner sixty-five years of age. This rate was similar to the revision rate for stanar total hip arthroplasty in this specific patient group. A higher revision rate was foun in women, patients with osteonecrosis, patients with inflammatory arthritis, an patients with evelopmental ysplasia of the hip. In contrast, Stulberg et al. reporte no higher failure rate among patients with osteonecrosis when hip resurfacing was compare with stanar total hip arthroplasty. Amstutz et al. escribe the largest single-surgeon hip resurfacing experience in the Unite States in a report on 1000 hips. There was a istinct ifference between the initial 300 hips an the subsequent 300 hips as the clinical experience increase. The implant survival rate was 91.8% for the early group an 98.4% for the later group at the time of the five-year follow-up. The islocation rate was 0.9%. These ata unerscore the importance of patient selection an surgical experience in optimizing the intermeiate-term success of hip resurfacing arthroplasty. Della Valle et al. reporte on the collective experience of Unite States surgeons with hip resurfacing following its approval in Data were collecte for the first 600 proceures. The uration of follow-up was short (three to six months). Averse events were ocumente in forty-one cases (6.8%); these events inclue eleven reoperations (nine of which were performe for the treatment of a femoral neck fracture) an seven cases each of nerve palsy an islocation. Longer followup is critical to etermine if complications will increase or will become less frequent with more clinical experience. Navigation an Computer-Assiste Surgery in Hip Resurfacing Navigation has been use in an effort to increase the accuracy an consistency of hip arthroplasty component position. Most stuies have emonstrate equal or superior accuracy in association with the use of navigation systems as compare with manual techniques. In one stuy, navigation was use to etermine if the learning curve for hip resurfacing coul be reuce. Twenty surgeons were ranomize into three groups with ifferent tasks for guiewire placement into the femoral hea. The mean error from the ieal position was 23 in association with the manual technique an 7 in association with navigation. Schnurr et al. performe a stuy of thirty hip resurfacing proceures in which the manual technique was compare with the navigation-assiste technique. They foun less varus positioning of the femoral component in association with the use of navigation. The learning curve associate with the use of navigation was long, but the set-up time was reuce to fifteen minutes with experience. In summary, these preliminary ata are encouraging. It remains to be etermine whether the avantage of an optimize femoral resurfacing component position woul outweigh the extra costs, substantial learning curve, an aitional operating time associate with the use of navigation. Complications of Hip Resurfacing Arthroplasty One of the most feare complications of hip resurfacing is femoral neck fracture. Marker et al. 16 reviewe 550 hip resurfacing proceures that ha been performe by a single surgeon. Twelve of the fourteen femoral neck fractures occurre in association with the first sixty-nine proceures. The fracture rate was 0.4% (two of 481 hips) after the initial learning curve. Women an obese patients were more likely to have a fracture. In another prospective multicenter stuy, Mont et al. 17 compare an initial cohort of 292 patients with a secon cohort of 724 patients. The ifference was that refinement of the surgical technique an patient selection criteria were institute in the secon group. The overall complication rate ecrease from 13.4% to 2.1%. More importantly, the femoral neck fracture rate ecrease from 7.2% to 0.8%. Data from both stuies emphasize the importance of proper patient selection an precise surgical technique when performing hip resurfacing arthroplasty. Femoral neck notching has been cite as perhaps the most important factor leaing to an increase risk of femoral neck fracture. Noiseux et al., in a caaveric biomechanical stuy, create ifferent situations with regar to femoral neck notching an varus component positioning. Varus positioning was foun to be the most important factor leaing to femoral neck fracture. In fact, femoral neck notching was not foun to cause a reuction in the loa neee to create a fracture. Most surgeons who are experience in resurfacing arthroplasty strongly recommen the avoiance of both femoral neck notching an varus component positioning uring hip resurfacing arthroplasty. Concerns about metal ion levels have been raise not only for resurfacing but for any metal-on-metal coupling. Controversies exist with regar to the ifference in accuracy when analyzing ion levels from the serum or the whole bloo. Venittoli et al. 18 reporte that serum ion levels were 1.39 an 1.37 times higher than whole bloo levels for chromium an cobalt, respectively, in sixty-four patients. Age an activities i not affect ion levels. De Haan et al. 19 measure ion levels in a competitive athlete who ha unergone hip resurfacing. A marke elevation in ion levels returne to baseline after six ays. Daniel et al. analyze urine ion levels prospectively at stanar intervals up to six years following hip resurfacing surgery. There was an increase of ion levels, reaching the

8 2049 maximum at six months to one year after surgery, an then there was a steay ecrease over the following five years. The whole bloo chromium level was significantly lower at the sixyear interval than at the one-year interval (p < 0.05). This reuction was a function of the patient s ability to clear the ions provie there was no increase in ion prouction from the bearing surfaces. Finally, implant position has an influence on ion levels. Hart et al. reporte higher ion levels in patients with a cup inclination of >56 as compare with patients with a cup inclination of <42. In some patients, the ion levels were more than tenfol higher. More stuies have been reporte with regar to lymphocyte aggregation, ALVAL (aseptic lymphocytic vasculitisassociate lesions), an metal hypersensitivity. Panit et al. reporte soft-tissue masses (pseuotumors) aroun hip resurfacing components in sixteen patients. All of the patients were women without a known history of metal allergy. The presenting symptoms inclue pain (twelve patients), a palpable lump (three), neurological symptoms (two), a sense of instability an subluxation (two), an spontaneous hip islocation (one). White bloo-cell counts were within normal limits in all cases, whereas inflammatory markers were elevate in 50%. Ultrasonography or magnetic resonance imaging emonstrate either a soli or a cystic mass arising from the hip joint. Histological analysis typically showe lymphocyte aggregates without polymorphonuclear leukocytes. The surgeons recommene revision to a conventional total hip replacement with a metal-on-polyethylene bearing. This problem may be relate to metallurgy an the manufacturing process of the implants use in these patients. Campbell et al. also reporte perivascular infiltrates of inflammatory cells in hip joint tissues retrieve from the sites of faile hip resurfacings, an they believe that a metal hypersensitivity reaction was a possible cause of failure. Ball et al. 20 observe scallope bone remoeling in the posterior part of the femoral neck an aroun the acetabular component rim in fourteen hips. They hypothesize that these changes were ue to neck-cup impingement. The changes were not, however, associate with implant loosening or femoral neck fracture. Hing et al. 21 reporte similar finings. They foun femoral neck bone loss (>10% of the femoral neck iameter) in 28% of 163 hips following resurfacing. Interestingly, they foun no aitional reuction in the amount of femoral neck bone from the three-year to the five-year followup. They conclue that narrowing of the femoral neck was not associate with any averse clinical or raiographic outcome up to a maximum of six years after the operation. Similar to the pseuotumors escribe above, longer-term follow-up is critical to further efine the clinical relevance of these bone remoeling changes aroun hip resurfacing implants. Conversion of a faile hip resurfacing to a stanar total hip arthroplasty is theorize to be relatively simple. In the stuy by Ball et al. 20, the results of twenty-one conversions that ha been performe following the failure of hip resurfacing were compare with those of sixty-four primary total hip arthroplasties that ha been performe for the treatment of osteoarthritis. There were no ifferences between the groups with regar to operative time, intraoperative bloo loss, or the complication rate, an the functional outcome was similar for the groups at a mean of four years of follow-up. Mont et al. reporte similar outcome ata when twenty-four conversions were compare with a matche cohort of primary total hip arthroplasties. Minimal Incision Surgery The initial enthusiasm brought about by the introuction of minimal incision hip arthroplasty appears to have graually ecrease over the past few years. Sustaine superior functional outcome following minimal incision surgery has not been conclusively ocumente. Moreover, an increase in complications has been ocumente in many clinical series. Minimal incision surgery has contribute to the evelopment of newer tissue-preserving surgical techniques, moifications of instruments an implants, the introuction of multimoal analgesia, the refinement of postoperative rehabilitation protocols, an, in some centers, accelerate patient ischarge an return to function. Dorr et al. 22 conucte a prospective stuy of 231 patients in which the efficacy of minimal incision surgery was compare with that of stanar-incision techniques involving the posterior approach. All proceures were performe by two experience senior surgeons, each of whom ha performe at least 100 minimal incision operations prior to the stuy. All patients were manage with ientical anesthesia, multimoal analgesia, an rehabilitation protocols. The minimal incision was an average of 10 cm in length, whereas the stanar incision was 20 cm in length. In all patients in the minimal incision group, the incision was extene to 20 cm at the completion of the operation in orer to control for the length of the incision itself an potential patient perception bias. The mean uration of the hospital stay was shorter in the minimal incision group. Patients in the minimal incision group were more likely to be ischarge in two ays an to use only a single assistive evice on ischarge. They also reporte less pain on each of the postoperative ays until ischarge. There was no ifference between the groups at six weeks or three months after surgery with regar to gait an pain level. There were no ifferences between the two groups with regar to cup position, stem orientation, limb lengths, offset measurement, or complications. Lin et al. 23 evaluate hip muscle strength, walking spee, an functional scores in a stuy in which fifty-three patients who ha unergone hip arthroplasty with use of a minimal anterolateral incision were compare with fifty-three patients who ha unergone hip arthroplasty with use of a stanar anterolateral incision. The major ifference in the approaches was the amount of hip abuctor release from the greater trochanter. During the first year after surgery, patients with the

9 2050 minimal incision hip arthroplasty ha significantly better muscle strength, walking spee, an functional scores. There was no ifference between the groups after one year. Williams et al. 24 prospectively followe sixty-seven hips that were treate with the two-incision approach an compare them with twenty-eight hips that were treate with use of a stanar anterolateral approach. There was no ifference between the groups in terms of implant position or clinical outcome. However, neither of those stuies were ranomize. Patient satisfaction is often ifficult to quantify. Dorr et al. 25 performe psychological assessments an correlate the finings with patient satisfaction following minimal incision total hip arthroplasty. A questionnaire was aministere to 165 patients before surgery an at various intervals after surgery. A minimal incision was use in 109 patients, an a stanar incision was use in fifty-six. Incision length was foun to be a factor that influence patient satisfaction at six weeks. This ifference was not observe beyon the short term because all of the patients were satisfie at the time of longer follow-up, regarless of the incision length. Forty percent of the patients with suboptimal satisfaction in the group with a stanar incision were foun to have other confouning reasons, inepenent of the incision length, that contribute to their issatisfaction. Minimal incision surgery is technically ifficult. Berger et al. reporte on the prospective clinical experience of four surgeons who began performing total hip arthroplasty with use of a minimal incision approach without formal training. Each surgeon performe 100 proceures. The collective complication rate associate with the first thirty-five operations was high (8%). The complication rate was reuce to 6%, 1%, an 0% for each subsequent 100 operations, respectively. This fining raises concerns with regar to the utility of minimal incision techniques in light of a high initial complication rate an no ocumente sustaine superior clinical outcome beyon the short term. The minimal incision approach has been extene to hip resurfacing arthroplasty. Chena et al. reporte on 136 hip resurfacing proceures that were performe with use of a 7-cm gluteus maximus-splitting approach. They reporte no more frequent complications as compare with their previous experience with use of a stanar posterior approach. A satisfactory result was recore for 97% of the patients at the time of the two-year follow-up. Piriou et al. reporte on 100 hip resurfacing proceures that were performe with use of a moifie minimal anterior incision. They reporte no increase in operative time or in the rate of complications as compare with their previous experience with the posterior surgical approach. There was one femoral neck fracture. Complications Venous Thromboembolism Venous thromboembolic isease is common following hip arthroplasty. Intense ebate has focuse on which prophylaxis methoology is most effective an safe. This topic was one of the most iscusse clinical issues in the past year with the introuction of the Surgical Care Improvement Project manate by the Unite States Centers for Meicare an Meicai Services an other health-care purchasers in The American Acaemy of Orthopaeic Surgeons (AAOS) recently publishe clinical guielines with regar to venous thromboembolic isease prophylaxis in orthopaeic patients. Differences between the AAOS guielines an the American College of Chest Physicians (ACCP) guielines have le to controversy not just among surgeons but also among meical isciplines an hospital aministrators. The orthopaeic community has long maintaine that the clinical relevance of venous thromboembolic isease shoul not be base solely on the prevalence of asymptomatic lesions on venographic stuies as reporte in well-esigne multicenter clinical trials. Dorr et al. 26 retrospectively reviewe the results of 1179 total joint arthroplasties in 970 patients. The patients were stratifie as being at low risk for venous thromboembolic isease (1046 operations) or at high risk for venous thromboembolic isease (133 operations). The low-risk group was manage with multimoal prophylaxis, incluing aspirin, ipyriamole, or clopiogrel bisulfate as well as intermittent calf pneumatic compression evices. The high-risk group was manage with ajuste-ose warfarin or low-molecular-weight heparin. All patients unerwent a screening venous Doppler scan before hospital ischarge. There were only three symptomatic pulmonary emboli, all in the low-risk group. There were five symptomatic eep-vein thrombi (prevalence, 0.4%) an sixty-one asymptomatic eep-vein thrombi (prevalence, 5.2%). A woun hematoma occurre in association with five (0.4%) of the operations; all were seen in patients who receive either warfarin or low-molecular-weight heparin. The authors conclue that multimoal prophylaxis without following the ACCP recommenations was effective an safe for selecte low-risk patients. Effective pharmacological prophylaxis may result in greater complications in the orthopaeic patient population. Parvizi et al. 27 reporte a higher prevalence of periprosthetic infection in patients who receive excessive pharmacological prophylaxis, which resulte in woun rainage an wounhealing problems. Sharrock et al. 28 conucte a meta-analysis evaluating the efficacy an safety of multimoal prophylaxis (incluing regional anesthesia, pneumatic compression, an aspirin) in 7193 patients. Those patients were compare with patients who receive either low-molecular-weight heparin (>15,000 patients) or warfarin (5000 patients). The authors reporte a higher mortality rate ue to all causes (0.41% compare with 0.19%) an a higher rate of nonfatal pulmonary emboli (0.60% compare with 0.35%) among patients receiving low-molecular-weight heparin as compare with those receiving the multimoal prophylaxis. Infection Reuction in the infection rate has been realize with timely aministration of perioperative antibiotic prophylaxis, a-

10 2051 vances in surgical technique, an moifications of the surgical suite. Ritter et al. 29 reviewe the results of 5980 total joint arthroplasties that ha been performe by a single surgeon, at a single institution, in ientical surgical suites, with use of the same surgical technique an perioperative management protocol, incluing antibiotics. The infection rate over this nineteen-year perio (from 1986 to 2005) was 1.77% (1.03% for hip arthroplasty an 2.20% for knee arthroplasty). The infection rate was effectively reuce to 0.57% (a threefol reuction) when ultraviolet light was installe in the operating suites. Ultraviolet light i not substantially ecrease the infection rate following hip arthroplasty (1.03% compare with 0.72%), but it i have an impact on the infection rate following knee arthroplasty (2.20% compare with 0.50%). Regression analysis emonstrate that revision surgery, previous infection, age, boy mass inex, cement fixation, an iagnosis ha no effect on the rate of infection. These ata are important as they reflect the infection rate associate with the use of contemporary surgical techniques an perioperative management protocols. The clinical efficacy of appropriately time antibiotic aministration has been ocumente in many stuies. Compliance, however, has been poor. Rosenberg et al. 30 evaluate the utility of aing confirmation of antibiotic aministration to the surgical timeout for wrong-site surgery in the operating room. The stuy inclue all patients who unerwent spine surgery, total hip arthroplasty, an total knee arthroplasty. The mean time between antibiotic aministration an skin incision was twenty-six minutes. This protocol resulte in a compliance rate of 99.1%. The authors also performe another retrospective analysis of forty patients who ha unergone total joint arthroplasty uring the three months prior to the institution of the protocol. The compliance rate was only 65% for that earlier patient subset. The compliance rate was maintaine at 97% in the eighteen months following the termination of the stuy perio, reflecting the effectiveness of changing a practice pattern at their institution. A two-stage reimplantation protocol is the most commonly utilize metho in the treatment of eep periprosthetic infection following total hip arthroplasty. Controversy remains with regar to which iagnostic criteria are best to exclue persistent infection. Bori et al. 31 reviewe the results of frozensection histological analysis for twenty-one patients who unerwent reimplantation. Seven of the twenty-one patients ha positive intraoperative cultures. The sensitivity, specificity, positive preictive value, an negative preictive value were 28.5%, 100%, 100%, an 73.6%, respectively, if the histological criterion was a minimum of five neutrophils seen in at least five high-power fiels. Although the ata ocumente a high probability of persistent infection if the results of frozensection histological analysis emonstrate more than five neutrophils per high-power fiel, it was not possible to completely rule out infection if the neutrophil count was less than five. It is perhaps best to use a combination of clinical infection markers an frozen-section histological analysis to formulate a final ecision regaring reimplantation. Dislocation Sah an Estok 32 compare the rate of islocation following conversion hip arthroplasty performe after the failure of a previous hemiarthroplasty with that following revision arthroplasty performe after the failure of a previous total hip arthroplasty. The hypothesis was that there might be a higher islocation rate in the conversion group because of the nee to ownsize the femoral hea iameter when the conversion arthroplasty was performe. There were eighty-nine hips in the conversion group an 115 hips in the revision group. The rate of islocation was significantly higher in the conversion group than in the revision group (22% compare with 10%). There was no ifference between hips with an without islocation in terms of cup iameter or position. A smaller femoral hea size contribute to a higher probability of islocation. The authors recommene maximizing femoral hea size an balancing soft-tissue tension when converting a previous hemiarthroplasty to a total hip arthroplasty. Periprosthetic Femoral Fracture Periprosthetic femoral fractures often occur in elerly patients with associate meical comorbiities. In the stuy by Bhattacharyya et al. 33, a cohort of 106 patients with periprosthetic femoral fractures was compare with 309 patients with hip fractures an 311 patients who unerwent primary total hip or total knee arthroplasty (controls). The comparator groups were matche for age an sex. The one-year mortality rate was 11% for the periprosthetic fracture group, compare with 2.9% for the primary total joint arthroplasty group. The mortality rate for the periprosthetic fracture group was similar to that for the hip fracture group (16.5% in both groups). Seventy-three of these periprosthetic fractures were Vancouver type-b fractures. Forty-nine of the seventy-three fractures were treate with revision hip arthroplasty, whereas twenty-four were treate with open reuction an internal fixation. The mortality rate was significantly lower in the revision group than in the open reuction an internal fixation group (12% compare with 33%; p < 0.03). However, the sample size was too small to etermine if the preferre treatment metho for Vancouver type-b fractures shoul be revision hip arthroplasty rather than open reuction an internal fixation. Taunton et al. reviewe a large cohort of 3346 primary total hip arthroplasties that ha been performe with use of a cementless proximally-coate femoral stem from 1987 to 2007 at two institutions. Forty-one hips (1.2%) ha an acute postoperative periprosthetic femoral fracture. Twenty-eight of these fractures were isplace, unstable fractures. The fractures occurre an average of twenty-eight ays (range, four to eightyeight ays) after surgery. Nineteen of these patients with a fracture were still using walking ais. There was a significant increase in the fracture rate uring the last three years of the

11 2052 stuy perio. The authors attribute this increase to the contemporary practice pattern in the Unite States: smaller incisions, accelerate rehabilitation, an higher utilization of cementless stems. Practice Management Specialty Hospitals The recent emergence of specialty hospitals focusing on proceural aspects of meicine has generate wiesprea controversy. Arguments have centere aroun (1) whether quality is improve an (2) whether specialty hospitals preselect patients with a low risk profile. Cram et al. 34 conucte a retrospective cohort stuy of 51,788 Meicare beneficiaries who unerwent total hip arthroplasty an 99,765 who unerwent total knee arthroplasty in thirty-eight specialty orthopaeic hospitals an 517 general hospitals between 1999 an The emographic ata an the ratio of primary to revision arthroplasties were similar. However, patients in specialty hospitals ha fewer comorbiities an resie in more affluent zip coes. More proceures were performe in specialty hospitals for both hip an knee arthroplasties. The unajuste rate of averse outcomes was lower in specialty hospitals for total hip arthroplasty (3.0% compare with 6.9%) an for total knee arthroplasty (2.1% compare with 3.9%). The ifferences were even more pronounce after ajusting for patient profile an proceure volume. These ata i substantiate better patient outcomes at specialty hospitals in the Meicare population. Major ifferences exist between countries with regar to health-care elivery, clinical protocols, an patient outcomes. Peterson et al. 35 reporte ata on the effectiveness of transferring a best-practice moel from the Unite States to the Unite Kingom with regar to reuction of the length of stay in the hospital following total hip arthroplasty. The reporte mean length of stay in the Unite Kingom was eleven ays in In fact, <15% of the patients were ischarge in less than eight ays. The government electe to buil a new specialty hospital near Lonon for total hip arthroplasty. The benchmark process inclue partnering with a high-volume orthopaeic specialty hospital in the Unite States. A collaborative effort was unertaken to transfer the best-practice strategies an clinical protocols (surgical, anesthesia, rehabilitation) from the Unite States hospital to buil an evelop the new hospital in the Unite Kingom. Data were collecte for twelve months after the opening of the new hospital. The mean length of stay was 6.1 ays for the 615 patients, representing a 45.5% reuction from historical ata. Eighty-six percent of the patients were ischarge in less than eight ays. The infection rate was also reuce, from 1% to 0.16%. During the same twelve-month perio, 1506 hip arthroplasties were performe in the Unite States hospital. The mean length of stay was four ays. The only factor that was cite to account for the ifference in the length of hospitalization was age of the patient, with younger patients in the Unite States hospital. This stuy suggests that the transfer of best-practice strategies can be effective in improving outcomes an achieving potential cost reuction. Regional Analgesia Regional blocks for analgesia have gaine tremenous popularity in recent years. The use of regional anesthesia an analgesia techniques in patients receiving anticoagulants has been a subject of ebate. There are well-establishe guielines for using anticoagulants in patients receiving neuraxial blocks. There are no guielines for the use of peripheral nerve blocks in patients receiving anticoagulants. Chelly an Schilling 36 assesse the risk of hematoma formation relate to the concomitant use of peripheral nerve blocks an pharmacological anticoagulation in patients unergoing total joint arthroplasty. Over a three-year perio, 6935 blocks in 3588 patients were one at a single institution with use of stanar protocols. The blocks were either single or continuous an inclue three sites: lumbar plexus, femoral, an sciatic. The perineural catheters were remove (in the continuous cases) on the secon or thir postoperative ay. The anticoagulants inclue warfarin (50%), aspirin (23.8%), low-molecular-weight heparin (13.4%), an fonaparinux (12.8%). No hematomas were recore. The stuy ocumente the safety of placing a peripheral nerve block before the aministration of anticoagulation prophylaxis in patients unergoing total joint arthroplasty. Furthermore, the catheters can be safely remove while the patient is receiving pharmacological prophylaxis after surgery. Arthroplasty Surgeon Workforce Deficiency Demographic ata inicate that there will be a ramatic increase in the eman for total joint arthroplasty in the Unite States in the years to come. Even more important, it has been estimate that there will be a 137% increase in the eman for revision hip arthroplasty an a 601% increase in the eman for revision knee arthroplasty by the year There is a concern that the iscrepancy in the projecte eman an the supply of arthroplasty specialists will wien. The 2005 AAOS membership survey reflecte that only 7% of the responents ientifie themselves as a specialist in ault hip an knee surgery. These specialists performe an average of 9.2 primary an 2.8 revision total hip arthroplasties per month. An aitional 41% of the responents ientifie themselves as having a clinical interest (not a focus) in ault hip an knee reconstructive surgery. These surgeons performe an average of 2.4 primary hip arthroplasties an 0.4 revision hip arthroplasties per month. The same survey also ocumente that fewer orthopaeic surgeons performe primary an revision total hip arthroplasty in 2004 as compare with the numbers generate from the 1990 AAOS membership survey. Iorio et al. conucte a survey of the AAOS membership an program irectors for ault reconstructive surgery fellowships. Ninety percent of the 620 grauating orthopaeic resients in the Unite States selecte a postgrauate fellowship in 2005, but only 6% chose ault reconstruction. There were 119 ault

12 2053 reconstructive fellowship positions in sixty-two programs in 2006 to 2007, an 77.3% of the positions were fille at that time. In 2007 to 2008, only 61.7% of the positions were fille an 19.3% were fille by physicians who ha been traine outsie of the Unite States. The average age of a joint arthroplasty specialist in the Unite States is fifty-three years. The AAOS survey emonstrate that the average age of retirement for all orthopaeic surgeons was 63.3 years. As a consequence of these numbers, a critical shortage in the ault reconstructive surgeon workforce is preicte to occur over the next two ecaes. Declining financial reimbursement for total hip arthroplasty continues to be a source of concern. Hariri et al. 37 reporte that payments from Meicare an Meicai constitute an average of 33% of an orthopaeic surgeon s practice revenue in This figure represente an increase from 26% in Meicare reimbursement for a primary total hip arthroplasty ecline from $1718 in 1998 to $1361 in 2007, a 21% reuction. The reimbursement for revisions ecline from $2416 to $1862, a 23% reuction uring the same time interval. These were non-inflation-ajuste figures. The Centers for Meicare an Meicai Services recently mae a proposal to reuce the fees by an aitional 21%. Aitional fee reuctions will unoubtely affect the practice patterns of arthroplasty surgeons in the future. Meical-Legal Issues Arthroplasty surgery is especially susceptible to the risk of meical malpractice exposure. Upahyay et al. 38 surveye 422 active members of the American Association of Hip an Knee Surgeons. Eighty-nine percent of the responents ha performe >100 hip an knee arthroplasty operations per year, an 78% ha been name as efenant in at least one lawsuit alleging meical negligence. This figure is higher than the estimate incience of thirteen per 1000 for non-feerally employe practicing physicians reporte by the Henry J. Kaiser Family Founation in The averse outcomes most commonly relate to litigation following total hip arthroplasty were nerve injury, limb-length iscrepancy, infection, vascular injury, an islocation. These finings agree with those of previous reports ientifying arthroplasty as among the most commonly litigate orthopaeic proceures 39. Suggeste strategies for minimizing the risk of litigation inclue aherence to the prevailing efine stanar of care an patient safety strategies, thorough patient communication, management of patient expectations, expert execution of the surgery, timely recognition an treatment of complications an averse outcomes, an etaile meical recor ocumentation. Meicai programs in the Unite States can receive bonuses, subject to a cap, for reporting ata on certain quality measures. Bozic et al. 40 reporte that evience-base guielines for payfor-performance initiatives in arthroplasty surgery are yet to be fully evelope. Preliminary peer-reviewe ata have emonstrate a positive impact on the quality of health care from practice guielines an the institution of qualitymonitoring processes. Direct-to-Consumer Avertising Direct-to-consumer avertising (DTCA) for arthroplasty evices an surgical proceures is a common practice, an it remains controversial. Bozic et al. 41 surveye both surgeons an patients to examine the impact of irect-to-consumer avertising. Nearly all surgeons reporte encountering questions from patients that were riven by irect-to-consumer avertising, most frequently regaring minimal incision surgery an specific implant esigns. The majority of surgeons believe that irect-to-consumer avertising ha a negative impact on the surgeon-patient interaction. Oler surgeons (those with an age of more than fifty years) an more experience surgeons (those in practice for more than twenty-five years) were more likely to view irect-to-consumer avertising as a positive factor in terms of patient eucation an improving physician-patient communication. Patients perceive irectto-consumer avertising as positive with regar to gaining information on new technology, current implant esigns, an surgical techniques. The authors conclue that the ifferent perceptions between the surgeons an the patients unerscore the importance for further improvement in surgeon-patient communication, which unoubtely will improve patient outcomes an reuce litigation. Inustry-Surgeon Relationship Inustry-physician relationships are the subject of a national ebate. In a survey of 3167 Unite States physicians from various specialties, 94% reporte some relationship with inustry, ranging from receiving gifts to receiving rug samples 42. More than one-thir receive reimbursement for attening professional meetings or continuing meical eucation activities. More than one-quarter receive payments for consulting, giving lectures, or enrolling patients in clinical trials. In 2007, the American Acaemy of Orthopaeic Surgeons implemente Stanars of Professionalism (SOPs) relate to Orthopaeist Inustry Conflicts of Interest 43. These stanars serve as guielines that enable surgeons to best serve the interests of patients while avancing the scientific an acaemic missions of the profession. Pay-for-Performance Future government proposals to reform Meicare, such as the pay-for-performance (P4P) program will target quality rather than volume of services. The pay-for-performance program provies that surgeons participating in the Meicare an Evience-Base Orthopaeics The eitorial staff of The Journal reviewe a large number of recently publishe research stuies relate to the musculoskeletal system that receive a Level of Evience grae of I. Over 100 meical journals were reviewe to ientify these

13 2054 articles, which all have high-quality stuy esign. In aition to articles cite alreay in this Upate, five level-i articles were ientifie that were relevant to total hip arthroplasty. A list of these titles is appene to this review after the stanar bibliography. We have provie a brief commentary about each of the articles to help guie your further reaing, in an eviencebase fashion, in this subspecialty area. Java Parvizi, MD Department of Orthopaeic Surgery, Rothman Institute, Thomas Jefferson University School of Meicine, 925 Chestnut Street, Philaelphia, PA B. Sonny Bal, MD Department of Orthopaeic Surgery, University of Missouri School of Meicine, Missouri Hip an Knee Center, 204 N. Keene Street, Suite 102, Columbia, MO Michael H. Huo, MD Department of Orthopaeic Surgery, UT Southwestern Meical Center, 1801 Inwoo Roa, Dallas, TX aress: michael.huo@utsouthwestern.eu Michael A. Mont, MD The Rubin Institute for Avance Orthopeics, 2401 West Belveere Avenue, 5th Floor, Sinai Hospital of Baltimore, Baltimore, MD References 1. Min BW, Song KS, Bae KC, Cho CH, Kang CH, Kim SY. The effect of stem alignment on results of total hip arthroplasty with a cementless tapere-wege femoral component. J Arthroplasty. 2008;23: Walter WL, O Toole GC, Walter WK, Ellis A, Zicat BA. Squeaking in ceramic-onceramic hips: the importance of acetabular component orientation. J Arthroplasty. 2007;22: Lusty PJ, Tai CC, Sew-Hoy RP, Walter WL, Walter WK, Zicat BA. Thir-generation alumina-on-alumina ceramic bearings in cementless total hip arthroplasty. J Bone Joint Surg Am. 2007;89: Koo KH, Ha YC, Jung WH, Kim SR, Yoo JJ, Kim HJ. Isolate fracture of the ceramic hea after thir-generation alumina-on-alumina total hip arthroplasty. J Bone Joint Surg Am. 2008;90: Tower SS, Currier JH, Currier BH, Lyfor KA, Van Citters DW, Mayor MB. Rim cracking of the cross-linke Longevity polyethylene acetabular liner after total hip arthroplasty. J Bone Joint Surg Am. 2007;89: Currier BH, Currier JH, Mayor MB, Lyfor KA, Collier JP, Van Citters DW. Evaluation of oxiation an fatigue amage of retrieve Crossfire polyethylene acetabular cups. J Bone Joint Surg Am. 2007;89: Howie DW, Neale SD, Stamenkov R, McGee MA, Taylor DJ, Finlay DM. Progression of acetabular periprosthetic osteolytic lesions measure with compute tomography. J Bone Joint Surg Am. 2007;89: Abeyta PN, Mamba RS, Janku GV, Murray WR, Kim HT. Reconstruction of major segmental acetabular efects with an oblong-shape cementless prosthesis: a long-term outcomes stuy. J Arthroplasty. 2008;23: Palm L, Jacobsson SA, Kvist J, Linholm A, Ojersjö A, Ivarsson I. Acetabular revision with extensive allograft impaction an uncemente hyroxyapatite-coate implants. Results after 9 (7-11) years follow-up. J Arthroplasty. 2007;22: Hamilton WG, McAuley JP, Tabaraee E, Engh CA Sr. The outcome of rerevision of an extensively porous-coate stem with another extensively porous-coate stem. J Arthroplasty. 2008;23: Parvizi J, Tarity TD, Slenker N, Wae F, Trappler R, Hozack WJ, Sim FH. Proximal femoral replacement in patients with non-neoplastic conitions. J Bone Joint Surg Am. 2007;89: Garbuz DS, Hu Y, Kim WY, Duan K, Masri BA, Oxlan TR, Burt H, Wang R, Duncan CP. Enhance gap filling an osteoconuction associate with alenronatecalcium phosphate-coate porous tantalum. J Bone Joint Surg Am. 2008;90: Le Duff MJ, Amstutz HC, Dorey FJ. Metal-on-metal hip resurfacing for obese patients. J Bone Joint Surg Am. 2007;89: McBrye CW, Revell MP, Thomas AM, Treacy RB, Pynsent PB. The influence of surgical approach on outcome in Birmingham hip resurfacing. Clin Orthop Relat Res. 2008;466: Steffen R, O Rourke K, Gill HS, Murray DW. The anterolateral approach leas to less isruption of the femoral hea-neck bloo supply than the posterior approach uring hip resurfacing. J Bone Joint Surg Br. 2007;89: Marker DR, Seyler TM, Jinnah RH, Delanois RE, Ulrich SD, Mont MA. Femoral neck fractures after metal-on-metal total hip resurfacing: a prospective cohort stuy. J Arthroplasty. 2007;22(7 Suppl 3): Mont MA, Seyler TM, Ulrich SD, Beaule PE, Boy HS, Grecula MJ, Golberg VM, Kenney WR, Marker DR, Schmalzrie TP, Sparling EA, Vail TP, Amstutz HC. Effect of changing inications an techniques on total hip resurfacing. Clin Orthop Relat Res. 2007;465: Venittoli PA, Mottar S, Roy AG, Dupont C, Lavigne M. Chromium an cobalt ion release following the Duron high carbon content, forge metal-on-metal surface replacement of the hip. J Bone Joint Surg Br. 2007;89: De Haan R, Campbell P, Rei S, Skipor AK, De Smet K. Metal ion levels in a triathlete with a metal-on-metal resurfacing arthroplasty of the hip. J Bone Joint Surg Br. 2007;89: Ball ST, Le Duff MJ, Amstutz HC. Early results of conversion of a faile femoral component in hip resurfacing arthroplasty. J Bone Joint Surg Am. 2007;89: Hing CB, Young DA, Dalziel RE, Bailey M, Back DL, Shimmin AJ. Narrowing of the neck in resurfacing arthroplasty of the hip: a raiological stuy. J Bone Joint Surg Br. 2007;89: Dorr LD, Maheshwari AV, Long WT, Wan Z, Sirianni LE. Early pain relief an function after posterior minimally invasive an conventional total hip arthroplasty. A prospective, ranomize, bline stuy. J Bone Joint Surg Am. 2007;89: Lin DH, Jan MH, Liu TK, Lin YF, Hou SM. Effects of anterolateral minimally invasive surgery in total hip arthroplasty on hip muscle strength, walking spee, an functional score. J Arthroplasty. 2007;22: Williams SL, Bachison C, Michelson JD, Manner PA. Component position in 2-incision minimally invasive total hip arthroplasty compare to stanar total hip arthroplasty. J Arthroplasty. 2008;23: Dorr LD, Thomas D, Long WT, Polatin PB, Sirianni E. Psychologic reasons for patients preferring minimally invasive total hip arthroplasty. Clin Orthop Relat Res. 2007;458: Dorr LD, Genelman V, Maheshwari AV, Boutary M, Wan Z, Long WT. Multimoal thromboprophylaxis for total hip an knee arthroplasty base on risk assessment. J Bone Joint Surg Am. 2007;89: Parvizi J, Ghanem E, Joshi A, Sharkey PF, Hozack WJ, Rothman RH. Does excessive anticoagulation preispose to periprosthetic infection? J Arthroplasty. 2007;22: Sharrock NE, Gonzalez Della Valle A, Go G, Lyman S, Salvati EA. Potent anticoagulants are associate with a higher all-cause mortality rate after hip an knee arthroplasty. Clin Orthop Relat Res. 2008;466: Ritter MA, Olbering EM, Malinzak RA. Ultraviolet lighting uring orthopaeic surgery an the rate of infection. J Bone Joint Surg Am. 2007;89: Rosenberg AD, Wambol D, Kraemer L, Begley-Keyes M, Zuckerman SL, Singh N, Cohen MM, Bennett MV. Ensuring appropriate timing of antimicrobial prophylaxis. J Bone Joint Surg Am. 2008;90:

14 Bori G, Soriano A, García S, Mallofré C, Riba J, Mensa J. Usefulness of histological analysis for preicting the presence of microorganisms at the time of reimplantation after hip resection arthroplasty for the treatment of infection. J Bone Joint Surg Am. 2007;89: Sah AP, Estok DM 2n. Dislocation rate after conversion from hip hemiarthroplasty to total hip arthroplasty. J Bone Joint Surg Am. 2008;90: Bhattacharyya T, Chang D, Meigs JB, Estok DM 2n, Malchau H. Mortality after periprosthetic fracture of the femur. J Bone Joint Surg Am. 2007;89: Cram P, Vaughan-Sarrazin MS, Wolf B, Katz JN, Rosenthal GE. A comparison of total hip an knee replacement in specialty an general hospitals. J Bone Joint Surg Am. 2007;89: Peterson MG, Cioppa-Mosca J, Finerty E, Graziano S, King S, Sculco TP. Effectiveness of best practice implementation in reucing hip arthroplasty length of stay. J Arthroplasty. 2008;23: Chelly JE, Schilling D. Thromboprophylaxis an peripheral nerve blocks in patients unergoing joint arthroplasty. J Arthroplasty. 2008;23: Hariri S, Bozic KJ, Lavernia C, Prestipino A, Rubash HE. Meicare physician reimbursement: past, present, an future. J Bone Joint Surg Am. 2007;89: Upahyay A, York S, Macaulay W, McGrory B, Robbennolt J, Bal BS. Meical malpractice in hip an knee arthroplasty. J Arthroplasty. 2007;22(6 Suppl 2): Attarian DE, Vail TP. Meicolegal aspects of hip an knee arthroplasty. Clin Orthop Relat Res. 2005;433: Bozic KJ, Smith AR, Mauerhan DR. Pay-for-performance in orthopaeics: implications for clinical practice. J Arthroplasty. 2007;22(6 Suppl 2): Bozic KJ, Smith AR, Hariri S, Aeoye S, Gourville J, Maloney WJ, Parsley B, Rubash HE. The impact of irect-to-consumer avertising in orthopaeics. Clin Orthop Relat Res. 2007;458: Campbell EG, Gruen RL, Mountfor J, Miller LG, Cleary PD, Blumenthal D. A national survey of physician-inustry relationships. N Engl J Me. 2007;356: Heckman JD. Patient care, professionalism, an relationships with inustry. J Bone Joint Surg Am. 2008;90:225. Evience-Base Articles Relate to Total Hip Arthroplasty Skegel C, Goeree R, Pleasance S, Thompson K, O Brien B, Anerson D. The cost-effectiveness of extene-uration antithrombotic prophylaxis after total hip arthroplasty. J Bone Joint Surg Am. 2007;89: The risk of venous thromboembolism extens beyon the hospital stay after total hip arthroplasty. This stuy evaluate the cost-effectiveness of extene prophylaxis. The health benefits were measure as a reuction in the rates of symptomatic thromboembolism an eath. The treatments that were analyze inclue low-molecular-weight heparin, warfarin, an no prophylaxis. The authors analyze stuies with extene prophylaxis to twenty-eight ays or more. They foun a net gain in quality-ajuste life years in both cohorts receiving pharmacological extene prophylaxis relative to the cohort receiving none. Cost-effectiveness analysis emonstrate $106,454 per qualityajuste life year gaine for low-molecular-weight heparin an $13,115 for warfarin. The authors conclue that there was insufficient economic evience to support extene prophylaxis with low-molecular-weight heparin following total hip arthroplasty. Aitional stuies are necessary to valiate whether extene prophylaxis with use of warfarin is cost-effective. Anersen KV, Pfeiffer-Jensen M, Haralste V, Søballe K. Reuce hospital stay an narcotic consumption, an improve mobilization with local an intraarticular infiltration after hip arthroplasty: a ranomize clinical trial of an intraarticular technique versus epiural infusion in 80 patients. Acta Orthop. 2007;78: This prospective ranomize stuy was conucte to compare epiural analgesia with intra-articular infiltration an infusion of a multi-rug regimen (ropivacaine, ketorolac, an epinephrine) in eighty patients following total hip arthroplasty. Both protocols were continue to twenty-four hours after surgery. There was no ifference between the groups with regar to the pain level uring the first twenty-four hours. However, after cessation of treatment, there was significantly less pain in patients receiving the intra-articular infusion. Moreover, there was a significant reuction in narcotic use an the length of hospital stay in the infusion group. Innovative an effective postoperative analgesia can contribute to improve outcomes an cost-effectiveness in total hip arthroplasty. Jolles BM, Bogoch ER. Posterior versus lateral surgical approach for total hip arthroplasty in aults with osteoarthritis. Cochrane Database Syst Rev. 2006;3:CD Many previous stuies have ocumente ifferences between these two most commonly utilize surgical approaches in performing total hip arthroplasty. This meta-analysis was conucte to etermine if there are any ifferences in terms of the risks of islocation, the prevalence of Trenelenburg gait, an sciatic nerve palsy. Only four stuies met all of the inclusion criteria. These four stuies inclue 241 patients. There was no significant ifference between the approaches in terms of the rates of islocation, Trenelenburg gait, or sciatic nerve palsy. However, there was a ifference between the posterior approach an the irect lateral approach with regar to overall rate of nerve complications (2% compare with 20%). The ifferences reporte in the past may be offset by moern prosthetic esigns an surgical techniques. Venittoli PA, Lavigne M, Girar J, Roy AG. A ranomise stuy comparing resection of acetabular bone at resurfacing an total hip replacement. J Bone Joint Surg Br. 2006;88: Acetabular component size is epenent on femoral sizing uring hip resurfacing arthroplasty. The surgeons ranomly assigne 210 hips to either hip resurfacing or traitional total hip arthroplasty. There was no ifference between the two groups with regar to the mean acetabular component size: mm for total hip arthroplasty an mm for hip resurfacing. The surgeons ha to use a larger acetabular component in seven resurfacing proceures (6.8%) in orer to match the femoral resurfacing size. There was no complication relate to the acetabular component in either group. The authors conclue that acetabular bone removal was similar for the two groups given this particular implant esign. Trampuz A, Piper KE, Jacobson MJ, Hanssen AD, Unni KK, Osmon DR, Manrekar JN, Cockerill FR, Steckelberg JM, Greenleaf JF, Patel R. Sonication of remove hip an knee prostheses for iagnosis of infection. N Engl J Me. 2007;357: This prospective trial examine the utility of using sonication to remove material from retrieve implants for culture. The hypothesis was that higher yiel an accuracy woul be achieve with use of sonication. The stuy inclue 331 patients (207 knees an 124 hips). Aseptic failure ha occurre in 252 patients, an septic failure ha occurre in seventy-nine. With use of ientical criteria to ocument infection, the sensitivity was greater with use of specimens obtaine by means of sonication (78.5% compare with 60.9%). There was no ifference in terms of specificity (98.8% compare with 99.2%). Fourteen cases of infection were etecte by means of sonicate-flui culture but not by means of culture of the periprosthetic tissue alone. Importantly, for patients who ha receive antimicrobial therapy within fourteen ays after surgery, the sensitivity was significantly better in association with the use of sonication (75% compare with 45%).