Outcomes of Liner Exchange Versus Component Revision for the Treatment of Stiffness Following Primary Total Knee Arthroplasty.

BACKGROUND: This study aimed to compare outcomes of revision total knee arthroplasty (rTKA) with liner exchange (LE) versus component revision (CRev) for stiffness post-TKA. METHODS: We retrospectively identified all rTKA performed for stiffness after primary TKA using our institutional database (2003 to 2021). Cases with infection, loosening, or < two years follow-up were excluded. There were 129 rTKA included, 91 in the LE, and 38 in the CRev cohorts. The mean follow-up was 8.5 years (range, two to 21). The LE and CRev cohorts had similar baseline demographics (P > 0.05), previous manipulation (P = 0.45), time from primary TKA (P = 0.14), and pre-rTKA arc of motion (AOM) (P = 0.08). The primary outcomes were the achievement of a successful range of movement (ROM), defined as flexion ≥ 90° with an extension deficit of ≤ 10°, and AOM improvement. Kaplan-Meier analysis was used to compare survival free from re-revision between cohorts. RESULTS: For the entire cohort, 69% achieved a successful ROM, and the mean AOM improved (P < 0.001). Achievement of successful ROM was comparable between LE (72%) and CRev (62%) cohorts (P = 0.29). The mean gain in AOM was similar between LE (24.9°) and CRev (25.4°) cohorts (P = 0.45). Preoperative extension deficit was associated with poorer outcomes (P = 0.006). The 10-year re-revision-free survival was similar between the LE (86.2%) and CRev (81.1%) cohorts (P = 0.55). Survival from re-revision for stiffness at 10-years was also similar (P = 0.6). The CRev group had increased surgical times (P < 0.0001), blood loss (P < 0.0001), and length of stay (P = 0.01). CONCLUSIONS: LE resulted in similar achievement of a successful ROM and re-revision-free survival compared with CRev. In properly selected patients, LE is a reasonable option for the treatment of stiffness after TKA.

Clinical Outcomes and Risk Factors for Re-Revision Due to Trunnion Corrosion in Primary Metal-on-Polyethylene Total Hip Arthroplasty.

BACKGROUND: There is a paucity of literature regarding the mid-term (greater than 2 years) outcomes of revision for adverse local tissue reaction to metal debris due to corrosion at the head-neck junction (trunnionosis) in metal-on-polyethylene total hip arthroplasty (THA), and risk factors for re-revision remain largely unknown. We aimed to report the re-revision-free survival and functional outcomes for this patient population and to identify risk factors for re-revision. METHODS: A total of 80 hips (79 patients) with a metal-on-polyethylene THA who had undergone revision for trunnionosis at our institution were included. The mean study follow-up from index trunnionosis revision was 4.6 years (range, 2.0 to 9.4). Kaplan-Meier survival analysis was performed with all-cause re-revision as the end point, and multivariate logistic regression was used to identify risk factors for re-revision. RESULTS: We saw that twenty-one hips (26%) underwent re-revision at a mean of 8.0 months (range, 0.03 to 36.3) after the index trunnionosis revision, most commonly for instability and infection. The two- and five-year all-cause re-revision-free survival rates were 75.0 and 73.2%, respectively. The mean Oxford Hip Score was 33.7 (range, 11 to 48); 76% were satisfied, and 24% were dissatisfied with their hip. Multivariate analysis identified not undergoing a cup revision (odds ratio: 4.5; 95% confidence interval: 1.03 to 19.7) and time from primary THA to the index trunnionosis revision (odds ratio: 0.77; 95% confidence interval: 0.62 to 0.97) as risk factors for undergoing re-revision. CONCLUSIONS: The risk of early re-revision for these patients is high (26%), mostly due to infection and instability, and functional outcomes are fair. Not performing a cup revision appears to be a risk factor for re-revision, as is the shorter time from primary THA to trunnionosis revision. LEVEL OF EVIDENCE: III.

Porous Tantalum Metaphyseal Cones for Severe Femoral and Tibial Bone Defects in Revision Total Knee Arthroplasty are Reliable for Fixation at Mean 5-Year Follow-Up.

BACKGROUND: Porous tantalum metaphyseal cones may facilitate reconstructions of severe bone defects during revision total knee arthroplasty (TKA), but there remains a paucity of data on their outcomes at mean 5 years of follow-up. This study reports the component survivorship, patient satisfaction, functional outcomes, radiographic osseointegration, and complications of revision TKA with porous tantalum metaphyseal cones at mid-term (mean 5-year) follow-up. METHODS: This study included 152 patients who had a mean age of 66 years (range, 33 to 86 years) undergoing revision TKA with porous tantalum metaphyseal cones. Indications for surgery included aseptic loosening (n = 87, 57.3%), second-stage reimplantation for infection (n = 42, 27.6%), osteolysis with well-fixed components (n = 20, 13.2%), and periprosthetic fracture (n = 3, 2.0%). Component survivorship, clinical outcomes, radiographic outcomes, and any complications were recorded. The mean follow-up time was 5.6 years (range, 2.2 to 13.7). RESULTS: Survivorship was 100% when the end point was revision of the metaphyseal cone (no cones were revised) and 83.8% (95% confidence interval: 77.9 to 90.2%) when the end point was reoperation for any reason at 5-year follow-up. Reoperations were performed for infection (n = 10), instability (n = 4), periprosthetic fracture (n = 2), and quadriceps rupture/dehiscence (n = 3). The mean patient satisfaction score was 78.8 ± 11.3 and the mean Forgotten Joint Score was 62.2 ± 16.7 at the final follow-up. The preoperative median University of California at Los Angeles score improved from 2 (interquartile range 2 to 3) to 6 points (interquartile range 5 to 6) (P < .001), and the preoperative Oxford knee score improved from 15.2 ± 3.8 to 39.4 ± 5.1 points (P < .001) at the final follow-up. All metaphyseal cones showed radiographic evidence of osteointegration without any subsidence or loosening. CONCLUSIONS: Porous tantalum metaphyseal cones enabled robust reconstructions of severe femoral and tibial bone defects during revision TKA. These reconstructions were associated with excellent survivorship, improvements in functional outcomes, and reproducible radiographic osseointegration at mean 5-year follow-up. The most common reasons for reoperation were infection and instability.

The John Charnley Award: The Impact of Human Leukocyte Antigen Genotype on Bacterial Infection Rates and Successful Eradication in Total Hip Arthroplasty.

BACKGROUND: Genetics play an important role in several medical domains; however, the influence of human leukocyte antigen (HLA) genotype on the development of periprosthetic joint infection (PJI) in total hip arthroplasty (THA) remains unknown. The primary aim of this study was to determine if HLA genotype is associated with the development of bacterial PJI in THA. Secondarily, we evaluated the association between HLA genotype and PJI treatment success. METHODS: A retrospective, matched, case-control study was performed using prospectively collected data from a single institution. A total of 49 patients who underwent primary THA were included, with a mean follow-up of 8.5 years (range, 4.2 to 12.9). The 23 cases (PJI) and 26 controls (no PJI) were matched for age, sex, follow-up, body mass index, primary diagnosis, and comorbidities (P > .05). High-resolution genetic analysis targeting 11 separate HLA loci was performed in all patients using serum samples. The HLA gene frequencies and carriage rates were determined and compared between cohorts. A subgroup analysis of PJI treatment success (18) and failure (5) was performed. Statistical significance was set at P = .10 for genetic analysis and at 0.05 for all other analyses. RESULTS: There were 4 HLA alleles that were significantly associated with the development of PJI. The 3 at-risk alleles included HLA-C∗06:02 (odds ratio 5.25, 95% CI [confidence interval] 0.96 to 28.6, P = .064), HLA-DQA1∗04:01 (P = .096), and HLA-DQB1∗04:02 (P = .096). The single protective allele was HLA-C∗03:04 (odds ratio 0.12, 95% CI 0.01 to 1.10, P = .052). There were no specific HLA alleles that were associated with treatment success or failure. CONCLUSIONS: This study suggests that there are at-risk and protective HLA alleles associated with the development of PJI in THA. To our knowledge, this is the first study to demonstrate an association between patient HLA genotype and the development of PJI. A larger study of the subject matter is necessary and warranted.

The Diagnostic Utility of Serum Metal Ion Markers for High-Grade Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesions (ALVALs) in Revision Hip and Knee Arthroplasty: An International Multicenter Study.

BACKGROUND: Aseptic lymphocyte-dominated vasculitis-associated lesions (ALVALs) are typically described in the context of metal-on-metal (MoM) hip bearings. This study explores the diagnostic utility of preoperative serum cobalt and chromium ion levels in determining the histological grade of ALVAL in revision hip and knee arthroplasty. METHODS: This was a multicenter retrospective review of 26 hips and 13 knees assessing the correlation between preoperative ion levels (mg/L (ppb)) and the histological grade of ALVAL from intraoperative specimens. The diagnostic ability of preoperative serum cobalt and chromium levels to determine high-grade ALVAL was assessed using a receiver operating characteristic (ROC) curve. RESULTS: In the knee cohort, there was a higher serum cobalt level in high-grade ALVAL cases (10.2 mg/L (ppb) versus 3.1 mg/L (ppb)) (P = .0002). The Area Under the Curve (AUC) was 1.00 (95% confidence interval (CI) 1.00 to 1.00). There was a higher serum chromium level in high-grade ALVAL cases (12.25 mg/L (ppb) versus 7.77 mg/L (ppb)) (P = .0002). The AUC was 0.806 (95% CI 0.555 to 1.00). In the hip cohort, there was a higher serum cobalt level in high-grade ALVAL cases (333.5 mg/L (ppb) versus 119.9 mg/L (ppb)) (P = .0831). The AUC was 0.619 (95% CI 0.388 to 0.849). There was a higher serum chromium level in high-grade ALVAL cases (186.4 mg/L (ppb) versus 79.3 mg/L (ppb)) (P = .183). The AUC was 0.595 (95% CI 0.365 to 0.824). CONCLUSIONS: Histologically, high-grade ALVAL has significantly higher preoperative serum cobalt and chromium ion levels in revision TKA. Preoperative serum ion levels have excellent diagnostic utility in revision TKA. Cobalt levels in revision THA have a fair diagnostic ability and chromium levels had a poor diagnostic ability.

Short-term survival of the cementless triathlon total knee arthroplasty in a young patient cohort.

BACKGROUND: The purpose of this study is to assess the short-term survivorship of a new cementless total knee arthroplasty (TKA) design in comparison to its cemented predecessor design in a young patient cohort less than 65 years of age. METHODS: We performed a retrospective cohort study of all primary TKAs (cemented and cementless) in patients under the age of 65 at the time of the index procedure, in a single institution between May 2018 and May 2019. Primary outcome variables included aseptic revision and all-cause revision. Operative time was a secondary variable. Independent variables considered included age, sex, body mass index (BMI), American Society of Anesthesiologists (ASA) grade, implant type (cruciate-retaining (CR) or posterior-stabilised (PS)) and the use of cemented or cementless implants. RESULTS: There were 106 cemented TKAs and 152 cementless TKAs (Triathlon, Stryker Inc, Mahwah, NJ ) implanted. The minimum follow-up for all cases was 2 years (mean cementless 32.5 months, mean cemented 34.9 months). Of the entire 258 implants only 2 were revised. Both revisions occurred in the cemented cohort for prosthetic joint infection (PJI). The all-cause revision rate in the cementless cohort was 0% compared to 1.8% in the cemented cohort (p = 0.168). Operative times were significantly reduced from 62 min in the cemented cohort to 52.2 min in the cementless cohort (p < 0.001). CONCLUSION: In a young patient cohort, the cementless Triathlon TKA demonstrates excellent survivorship at short-term follow-up with significant reductions in operative times when compared to the cemented Triathlon TKA.

Risk factors for failure of manipulation under anesthesia after total knee arthroplasty.

BACKGROUND: Manipulation under anesthesia (MUA) is a well-established treatment for stiffness after total knee arthroplasty (TKA). Risk factors for failure of MUA remain largely unknown. The primary aim of this study was to identify risk factors for failure of MUA after TKA. METHODS: We performed a retrospective cohort study including 470 patients who underwent MUA after primary TKA with minimum 2 year follow-up. Patients were grouped into success (n = 412) or failure (n = 58) cohorts; failure was defined as flexion < 90° at most recent follow-up or revision for stiffness. The increase in flexion post-MUA for the cohort was calculated. Several clinical, patient, and surgical factors were analyzed using univariate, followed by multivariable logistic regression models to identify independent risk factors associated with failure. RESULTS: The mean increase in flexion was 42° (range 0-115). BMI 30-35 (p = 0.01, odds ratio (OR) 2.42; 95% CI 1.25-4.68) and poorer pre-MUA flexion (p < 0.01, OR 1.43; 95% CI 1.23-1.67) were risk factors for failure. When considering revision for stiffness only, BMI 30-35 (p = 0.01, OR 3.27; 95% CI 1.41-7.61), lower pre-MUA flexion (p < 0.01, OR 1.43; 95% CI 1.18-1.75), and history of prior knee surgery (p = 0.04, OR 2.31; 95% CI 1.06-5.04) were predictors of failure. Time to MUA (p = 0.48), thromboprophylaxis (p = 0.44), pre-operative opioid use (p = 0.34), depression/anxiety (p = 1.0), and several other factors analyzed were not associated with failure. CONCLUSION: In this large cohort, elevated BMI and lower pre-MUA flexion were risk factors for failure of MUA. History of prior knee surgery was an additional predictor of requiring revision for stiffness.

Comparison of Clinical and Functional Outcomes in One versus Two Component Revision for Total Knee Arthroplasty.

BACKGROUND: Revisions of total knee arthroplasties (TKAs) may require revision of one or both tibial and femoral components. Our purpose was to examine the clinical and functional outcomes in 1- versus 2-component TKA revisions. METHODS: We identified 92 1-component (tibial or femoral) revisions at a single center. Our inclusion criteria were isolated revision of the tibial or femoral components with a minimum 2-year follow-up. The included cases were matched 1:2 with a control group of 2-component revisions (tibial and femoral) by age, body mass index, American Society of Anesthesiologists score, and indication for revision. We collected demographics, complications, operative times, any subsequent rerevisions, and functional outcome scores. RESULTS: The median follow-up time for the 1- and 2-component revision groups were 10 years (range, 3 to 17) and 8 years (range, 2 to 18), respectively. The most common complication after rerevision in both groups was stiffness at 9 of 92 (9.8%) and 9 of 170 (5.3%) in the 1- and 2-component groups, respectively (P = .20). The overall complication prevalence in the 1- and 2- component revision groups was similar 20 of 92 (22%) and 35 of 170 (21%), respectively (P = .87). Subsequent rerevisions for any indication were encountered in 12 of 92 (13.0%) of the 1-component and 18 of 170 (11%) in the 2-component groups (P = .69). There was no statistical difference in survivorship or functional outcomes scores between the groups. CONCLUSION: Our results showed that isolated revision of a single TKA component is an acceptable option, with comparable functional outcomes, complications, and survivorships when compared with both-component revision. As such, a 1-component revision should be considered where appropriate.

Malseating of Modular Dual Mobility Liners: High Prevalence in Revision Total Hip Arthroplasty.

BACKGROUND: Modular dual mobility (MDM) acetabular components have become increasingly more popular in total hip arthroplasty (THA). Uncertainty remains regarding liner malseating and its consequences after 5 to 10 years, especially in patients who undergo revision THA. The objective of this study was to analyze the prevalence of malseating and implant survivorship of patients who underwent revision THA using an MDM liner. METHODS: We retrospectively identified patients who had a minimum 2-year follow-up and underwent revision THA using an MDM liner. Patient demographics, implant details, mortality, and all-cause revisions were recorded. Patients who had radiographic follow-up were assessed for malseating. Kaplan-Meier survival was used to determine implant survivorship. We included 143 hips in 141 patients. Mean age was 70 years (35-93 years), and 86 patients (60.1%) were female. RESULTS: Overall implant survival was 89.3% (95% confidence interval (CI) 0.843-0.946) at a mean follow-up of 6 years (ranging from 2 to 10 years). There were eight patients excluded from malseating assessment. Upon radiological review, 15 liners (11.1%) were malseated. Survival for all-cause revision for patients with malseated liners was 80.0% (12/15, 95% CI 0.62 - 0.99, P = .15) versus 91.5% in patients who had nonmalseated liners (110/120, 95% CI 0.86-0.96). There were no intraprosthetic dislocations and 3.5% of the patients were revised due to instability. No liners were revised due to malseating, and no patients who had malseated liners were revised due to instability. CONCLUSIONS: Using MDM components in our cohort comprised of revision THA was associated with a high prevalence of malseating and an overall survival of 89.3% at a mean follow-up of 6 years. Malseating does not appear to impact implant survival at a mean follow-up of 6 years.

The Desired Oxford Knee Score Obtained Before Total Knee Arthroplasty is Predictive of the Postoperative Oxford Knee Score: A Prospective Study.

BACKGROUND: The relationship between patient expectations and patient-reported outcome measures (PROMs) after total knee arthroplasty (TKA) is not well understood. The purpose of the study was to test the influence of desired knee function on postoperative perceived knee function 1 year after TKA. METHODS: A total of 102 patients undergoing primary TKA were available for data analyses. Preoperatively, patients completed the Oxford Knee Score (OKS) twice, one representing preoperative function (preoperative OKS); the second representing desired function after TKA (desired OKS). Western Ontario and McMaster Universities Arthritis Index (WOMAC), University of California, Los Angeles (UCLA) Activity score, Hospital for Special Surgery Knee Replacement Expectations Survey (HSS-KRES), Patient Health Questionnaire-9, and EuroQol-visual analogue scales were obtained preoperatively. One year after surgery, all surveys besides the UCLA activity score and HSS-KRES were repeated. The associations between postoperative OKS and WOMAC versus desired OKS and HSS-KRES were assessed using multivariable linear regression models, wherein linear regression coefficients represent the additive effect on the mean postoperative PROM. RESULTS: The desired OKS was independently associated with the postoperative OKS (linear regression coefficient = 0.43; P = .011), that is, each point increase in desired OKS yielded a 0.43 increase in postoperative OKS. The preoperative OKS showed no association with postoperative PROMs. Desired OKS was correlated with postoperative WOMAC (coefficient = -0.67; P = .014). The HSS-KRES was not associated with the postoperative OKS (coefficient = -0.005; P = .965) or WOMAC (coefficient = 0.18; P = .288). CONCLUSION: In TKA patients, higher preoperative desired function predict greater postoperative PROMs. Effects of preoperative expectations on outcomes are independent of patient demographics or preoperative function.

International primary knee arthroplasty registry review: findings from current reports.

INTRODUCTION: International joint registries provide high volumes of information in relation to the performance of total knee arthroplasty on a global scale. Distillation of this data can be challenging, particularly with the establishment of more arthroplasty registries on a yearly basis. We therefore aim to present key information from these registries in relation to primary total knee arthroplasty. The specific questions of interest include: Which fixation type is superior in TKA? Does the level of constraint impact on clinical performance? How do partial knee replacements perform in the registries? Does patellar resurfacing lead to superior results? Are there any specific implants which perform particularly well or poorly? METHODS: A comprehensive review of the major English-speaking knee arthroplasty registries across the globe was performed. Given the expanding large number of registries worldwide, it was not possible to perform a comprehensive review of all registries and so, a detailed review of the major English-speaking knee arthroplasty registries was included. Key trends and developments in implant performance were identified and presented in the current article. RESULTS: Total knee replacements have lower revision rates than both unicompartmental and patellofemoral joint replacement procedures. Patellofemoral joint replacements have the highest failure rate of all knee replacement procedures. Cruciate-Retaining (CR) TKR designs have superior outcomes to Posterior-Stabilized (PS) designs across all registries. Patellar resurfacing appears to confer an advantage over non-resurfaced patellas in primary TKR. CONCLUSION: We present current global trends in the utility and performance of TKA based on data from English-speaking arthroplasty registries.

Has the incidence of total joint arthroplasty in rheumatoid arthritis decreased in the era of biologics use? A population-based cohort study.

OBJECTIVES: To determine whether the introduction of biological DMARDs (bDMARDs) was associated with reduced incidences of total hip and knee arthroplasty (THA/TKA) among patients with RA compared with OA. METHODS: Using a population-based cohort in British Columbia, Canada, RA and OA patients diagnosed between 1995 and 2007 were divided into semi-annual cohorts according to diagnosis date. For each cohort, we calculated 8-year incidence rates of THA and TKA. We compared levels and trends of THA/TKA incidence in RA/OA patients diagnosed during pre-bDMARDs (1995-2001) and post-bDMARDs (2003-2007) periods using interrupted time-series analysis, adjusting for baseline characteristics. Adjusted 8-year total joint arthroplasty incidence estimated for RA/OA cohorts diagnosed five years after bDMARDs introduction were compared with expected rates assuming no bDMARDs introduction, based on extrapolation of pre-bDMARDs trends. RESULTS: We identified 60 227 RA and 288 260 OA incident cases. For cohorts diagnosed pre-bDMARDs, 8-year THA/TKA incidence rates increased over time in both RA and OA. For cohorts diagnosed post-bDMARDs, these rates decreased over time in RA but continued to increase for OA. For RA, differences between the post- and pre-bDMARDs secular trends in incidence rates were -0.49 (P = 0.002) for THA and -0.36 (P = 0.003) for TKA, compared with +0.40 (P = 0.006) and +0.54 (P < 0.001), respectively, for OA. For RA cohorts diagnosed five years after bDMARDs introduction, 8-year incidences were 26.9% and 12.6% lower for THA and TKA, respectively, than expected rates. In contrast, corresponding rates in OA were higher by 11.7% and 16.6%, respectively. CONCLUSION: Arthritis onset after bDMARDs introduction is associated with a significant reduction in THA/TKA incidence in RA, but not in OA. The reduction reflects a significant improvement in RA treatment during the biological era.

Minimally Invasive Intermuscular Approaches Versus Conventional Approaches in Total Hip Arthroplasty: A Systematic Review and Meta-Analysis.

BACKGROUND: To date, the literature has not yet revealed superiority of Minimally Invasive (MI) approaches over conventional techniques. We performed a systematic review to determine whether minimally invasive approaches are superior to conventional approaches in total hip arthroplasty for clinical and functional outcomes. We performed a meta-analysis of level 1 evidence to determine whether minimally invasive approaches are superior to conventional approaches for clinical outcomes. METHODS: All studies comparing MI approaches to conventional approaches were eligible for analysis. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were adhered to throughout this study. Registries were searched using the following MeSH terms: 'minimally invasive', 'muscle-sparing', 'THA', 'THR', 'hip arthroplasty' and 'hip replacement'. Locations searched included PubMed, the Cochrane Library, ClinicalTrials.gov, the European Union (EU) clinical trials register and the International Clinical Trials Registry Platform (World Health Organisation). RESULTS: Twenty studies were identified. There were 1,282 MI total hip arthroplasty (THAs) and 1,351 conventional THAs performed. There was no difference between MI and conventional approaches for all clinical outcomes of relevance including all-cause revision (P = .959), aseptic revision (P = .894), instability (P = .894), infection (P = .669) and periprosthetic fracture (P = .940). There was also no difference in functional outcome at early or intermediate follow-up between the two groups (P = .38). In level I studies exclusively, random-effects meta-analysis demonstrated no difference in aseptic revision (P = .461) and all other outcomes between both groups. CONCLUSION: Intermuscular MI approaches are equivalent to conventional THA approaches when considering all-cause revision, aseptic revision, infection, dislocation, fracture rates and functional outcomes. Meta-analysis of level 1 evidence supports this claim.

The Impact of Changing Total Knee Arthroplasty Implants at a High-Volume Institution.

BACKGROUND: The ability of a group of high-volume arthroplasty surgeons to simultaneously change their preferred primary total knee arthroplasty (TKA) implant of choice to another, has not been explored in the literature to date. The main hypothesis was that such a change could be made with no significant impact on clinical outcomes. METHODS: This is a retrospective cohort study comparing the last 500 consecutive TKAs implanted of a routinely used TKA implant (NexGen; Zimmer, Warsaw, IN) with the first 500 consecutive TKAs implanted of a newly adopted TKA implant (Triathlon; Stryker, Mahwah, NJ) at an institutional level. Primary outcomes of importance included all complications that occurred either intraoperatively or early postoperatively, early all-cause revision rate, and early reintervention rate. RESULTS: There was a 1.2% (n = 6) complication rate in the NexGen cohort compared to 0.8% (n = 4) in the newly adopted Triathlon cohort (P = .75). The rate of intraoperative fracture was 1% in the NexGen cohort and 0.6% in the Triathlon cohort (P = .72). The early all-cause revision rate for the NexGen TKA was 1% (n = 5) compared to 0.8% (n = 4) in the Triathlon cohort (P = 1.0). The manipulation under anesthesia (MUA) rate in the NexGen cohort was 2.4% compared to 4.6% in the Triathlon cohort (P = .058). The only predictor variable associated with MUA rate was American Society of Anesthesiologists grade, where there was a significantly lower rate of MUA with a higher American Society of Anesthesiologists grade (P = .042). CONCLUSION: It is possible to implement the institution-wide adoption of an established, high-performing TKA implant without any negative implications in relation to early revision rates, perioperative complication rates, and reintervention rates. This study is the first of its kind to be reported in the literature.

Hybrid stems are superior to cemented stems in revision total knee arthroplasty: a systematic review and meta-analysis of recent comparative studies.

INTRODUCTION: The demand for revision total knee arthroplasty (TKA) has grown significantly in recent years. The two major fixation methods for stems in revision TKA include cemented and 'hybrid' fixation. We explore the optimal fixation method using data from recent, well-designed comparative studies. METHODS: We performed a systematic review of comparative studies published within the last 10 years with a minimum follow-up of 24 months. To allow for missing data, a random-effects meta-analysis of all available cases was performed. The odds ratio (OR) for the relevant outcome was calculated with 95% confidence intervals. The effects of small studies were analyzed using a funnel plot, and asymmetry was assessed using Egger's test. The primary outcome measure was all-cause failure. Secondary outcome measures included all-cause revision, aseptic revision and radiographic failure. RESULTS: There was a significantly lower failure rate for hybrid stems when compared to cemented stems (p = 0.006) (OR 0.61, 95% CI 0.42-0.87). Heterogeneity was 4.3% and insignificant (p = 0.39). There was a trend toward superior hybrid performance for all other outcome measures including all-cause re-revision, aseptic re-revision and radiographic failure. CONCLUSION: Recent evidence suggests a significantly lower failure rate for hybrid stems in revision TKA. There is also a trend favoring the use of hybrid stems for all outcome variables assessed in this study. This is the first time a significant difference in outcome has been demonstrated through systematic review of these two modes of stem fixation. We therefore recommend the use, where possible, of hybrid stems in revision TKA.

Pseudotumors and High-Grade Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesions Around Total Knee Replacements Identified at Aseptic Revision Surgery: Findings of a Large-Scale Histologic Review.

BACKGROUND: Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) development (including pseudotumors) secondary to metal debris generation around total hip arthroplasties is a well-recognized histopathologic phenomenon. Emerging data have highlighted a similar potential concern around TKAs although the body-of-knowledge has largely been limited to individual case reports or small retrospective case series. This study sought to establish the prevalence of pseudotumors or high-grade ALVALs seen at the revision of primary TKAs and to establish the correlation between histologic ALVAL grade and patient-reported functional outcome measures. METHODS: The findings of 321 non-infective (aseptic) patients undergoing unilateral revision knee surgery, at a high-volume tertiary referral center, were reviewed. Each case was independently histologically classified. Complete patient-reported functional outcome measures were available for 134 patients (42%) allowing correlation between functional performance and histopathology results. RESULTS: Five distinct pseudotumors and a further 18 high-grade ALVALs were histologically identified representing 1.6% and 5.6% of the cohort, respectively. When compared by histologic grade, Oxford Knee Score and Western Ontario and McMaster University's Osteoarthritis Index suggested a high correlation between ALVAL grade and functional knee scores. CONCLUSION: These findings suggest a prevalence of pseudotumors or high-grade ALVALs at revision TKA surgery of >7%. This unexpectedly high result may contribute insight into the previously under-appreciated significance of metal debris-related local tissue reactions around TKAs. The findings also demonstrate a strong near-linear inverse relationship between patient-reported clinical knee performance and the underlying histologic grade of local tissue reaction. These results have potential management implications for patients with underperforming TKAs and should prompt consideration of an ALVAL secondary to metallosis in the differential diagnosis. LEVEL OF EVIDENCE: This is a retrospective cohort study with Level III evidence.

Frank Stinchfield Award: Identification of the At-risk Genotype for Development of Pseudotumors Around Metal-on-metal THAs.

BACKGROUND: Once touted as the future of hip arthroplasty, metal-on-metal (MoM) bearing surfaces have fallen sharply from favor with the emergence of a strong body of evidence demonstrating unacceptably high premature implant failure rates. The previously unpredictable development of adverse local tissue reactions (ALTRs) has been a substantive contributor to this. Although the underlying pathophysiology of these so-called "pseudotumors" is now well understood, the fundamental predisposing patient risk factors have remained elusive. QUESTIONS/PURPOSES: The aim of this research, as a clinical-genotype correlation analysis, was to identify specific alleles (genes) associated with the development of ALTRs in patients with in situ MoM THAs. METHODS: A case-control study of patients who received a large-head, primary MoM THA between 2005 and 2008 was performed with a minimum followup of 5 years. Twenty-six patients who had undergone revision of a primary MoM THA secondary to symptomatic ALTRs were recruited. The mean timeframe from primary MoM THA to symptomatic revision was 5.5 years (range, 1-10 years). Twenty-eight control subjects were randomly selected asymptomatic patients with no evidence of ALTRs on protocol-specific screening. Baseline demographics and high-resolution genotype (human leukocyte antigen [HLA] Class II) were collected for all patients. Cohorts were similar with respect to age at the time of primary MoM THA (mean, 54.8 versus 54.9 years, p = 0.95) and serum cobalt (mean, 5.5 versus 8.5 µg/L, p = 0.09) and chromium concentrations (mean, 2.9 versus 4.2 µg/L, p = 0.27). The association between genotype and revision surgery secondary to ALTRs was determined with gender as a covariate. RESULTS: The prevalence of the risk genotype was 30% (16 of 54) among the entire cohort. Adjusting for sex, the odds of revision were 6.1 times greater among patients with the risk genotype present than among patients without (95% confidence interval [CI], 1.5-25.4; p = 0.01). Among females, the specificity of the risk genotype was 1.0 (95% CIexact, 0.5-1.0; pexact = 0.03), and for males, it was 0.8 (95% CIexact, 0.6-0.9; pexact < 0.01). CONCLUSIONS: The findings of this study suggest that, among patients with a primary MoM THA, allelic variation within the HLA Class II loci may be a strong, independent risk factor associated with the need for subsequent revision surgery secondary to pseudotumor formation. CLINICAL RELEVANCE: Given the hypothesis-generating nature of this novel undertaking, confirmatory prospective clinical studies are required to further elucidate this correlation and to explore the clinical utility of targeted genetic screening in this specific population. This research may, however, represent a key missing piece in the puzzle that is metal ion-induced pseudotumor formation.

A Comparison of Mobile and Fixed-Bearing Unicompartmental Knee Arthroplasty at a Minimum 10-Year Follow-up.

BACKGROUND: The long-term survivorship and functional outcomes of the mobile-bearing (MB) compared to the fixed-bearing (FB) unicompartmental knee arthroplasty (UKA) implant design remain a topic of debate. The aim of the current study was to compare the survivorship and functional outcomes of MB and FB UKA at a minimum 10-year follow-up. METHODS: We retrospectively reviewed 106 consecutive medial UKAs (89 patients) from our institution with a minimum 10-year follow-up. The 38 MB and 68 FB knees had follow-up of 14.2 years (12.9-15.5) and 11.5 years (10.2-15.1), respectively. Validated patient-reported outcomes and radiographs were evaluated as were etiology, timing, and complexity of revision. Kaplan-Meier 10-year survival was calculated with revision to total knee arthroplasty as the end point. RESULTS: The 10-year survival was 82.9% (95% confidence interval [CI] 65.8-91.9) for MB and 90.9% (95% CI 79.4-96.2) for FB UKA (P = .102), and 88.0% (95% CI 79.3-93.2) for the entire cohort. Patient outcomes were similar between groups, as were timing and etiologies for revision to total knee arthroplasty. One-third of revisions required either stems or tibial augments, and of these, all were of MB design. CONCLUSION: Survival and functional outcomes were similar between MB and FB designs. One-third of revisions required either stems or augments, all were of MB design.

An Early Report of the Use of a Modular Dual Mobility Articulation in Revision Acetabular Reconstruction.

BACKGROUND: Instability remains one of the main problems after revision hip surgery. The aim of this study was to review the clinical, radiological, and patient-reported outcomes with the use of modular dual-mobility articulation for revision acetabular reconstruction and investigate the risk of fretting corrosion by measuring serum trace metal ion levels. METHODS: Sixty consecutive patients with a minimum of 24-month follow-up after the insertion of a modular dual-mobility (Stryker, Mahwah, NJ) cup at the time of revision hip surgery were identified. Follow-up included clinical and radiological patient review and functional outcome measures, and a subset of patients had their metal ion (cobalt and chromium) levels checked. RESULTS: At the most recent follow-up, 5 patients had died, 3 patients have been revised because of ongoing instability, and 3 patients have had revision surgery due to infection. Overall functional outcome (mean Western Ontario and McMaster Universities Osteoarthritis Indexfunction 76, University of California, Los Angeles 5.6, mean Oxford 74.7, Short Form-12 physical 41.6/mental 53.3) and overall pain relief (mean Western Ontario and McMaster Universities Osteoarthritis Index pain score 78.3) scores were good. The mean satisfaction score was 78 of 100. The median serum trace metal chromium and cobalt levels at the most recent follow-up were 0.4 µg/L (range 0.1-6.1 µg/L) and 0.42 µg/L (range 0.21-9.42 µg/L), respectively. The survival with revision as the end point was 90%. CONCLUSIONS: Dual-mobility cups with modularity represent an excellent option for the patient having revision hip surgery at high risk of instability. This series presents good patient-reported outcome measures and a low complication and revision rate.

What Is the Natural History of Asymptomatic Pseudotumors in Metal-on-metal THAs at Mid-term Followup?

BACKGROUND: The risk of early revision because of pseudotumors in patients who have undergone large-head metal-on-metal (MoM) total hip arthroplasty (THA) is well documented. However, the natural history of asymptomatic pseudotumors or of MoM articulations without pseudotumors is less well understood. The aim of our study was to investigate the natural history of primary MoM THA at mid-term followup. QUESTIONS/PURPOSES: The purposes of this study were: (1) Did previously detected pseudotumors persist or worsen in asymptomatic patients at mid-term followup; and if so, did any of them require revision THA? (2) Did new pseudotumors form in asymptomatic patients at mid-term followup? (3) What happened to serum trace metal ions at mid-term followup? (4) Were postoperative patient-reported outcome measures (PROMs) maintained at mid-term followup? METHODS: Seventy-one patients who underwent a MoM THA using a Metasul LDH implant with a Durom acetabular cup and an M/L Taper stem between September 2005 and October 2008 were reviewed. All patients for this study were part of two previously published studies from our early followup. Data from the previous studies were used for comparison only. Two of the 71 patients (2.8%) were lost to followup. The mean age at operation was 56 years (range, 34-68 years). There were 24 female patients. All patients had serum trace metal ions testing, ultrasound imaging, and PROMs at a mean 3.5 years (early followup) after the index operation (range, 3-5 years) and delayed followup at a mean 7 years (range, 6.5-9 years). The indication to undertake revision THA was based on clinical evaluation and not solely on the investigation results. RESULTS: Twenty-three of 71 patients (32%) had a positive ultrasound scan for pseudotumor at early followup. Of these, eight patients underwent revision THA (11% of MoM THA or 35% of patients with an early positive ultrasound scan). The mean time between positive ultrasound scan and revision surgery was 13 months (range, 5-22 months). Of the remaining 15 patients with pseudotumor noted on early ultrasound, 12 had persistent pseudotumor, two resolved, and one was lost to followup. Six patients (13%) with a normal ultrasound scan at early followup showed new ultrasound findings at delayed followup. Of these, four (8%) were conclusively diagnosed as pseudotumor and one was revised. Serum trace metal ion increased at mid-term followup in the seven cases that showed an increase in volume of pseudotumor. Of the five patients in whom the volume of pseudotumor decreased on ultrasound at mid-term followup, three showed a decrease in serum trace ions levels, whereas two showed an increase. New-onset pseudotumors at mid-term followup was associated with an increase in serum trace metal ions at mid-term followup only in two of six cases. PROMs at mid-term followup of patients in this study remain high. CONCLUSIONS: At mid-term followup, approximately 35% of patients who develop an early pseudotumor undergo revision arthroplasty, whereas the remaining are asymptomatic. The incidence of new-onset ultrasound findings suggestive of pseudotumors at mid- to long-term followup is approximately 8% and these require continued surveillance. LEVEL OF EVIDENCE: Level II, prognostic study.