Risk of Revision for Fixed Versus Mobile-Bearing Primary Total Knee Replacements
ABSTRACT Mobile-bearing total knee arthroplasty prostheses were developed to reduce wear and revision rates; however, these benefits remain unproven. The purposes of this study were to compare the short-term survivorship and to determine risk factors for revision of mobile-bearing and fixed-bearing total knee replacements.
A prospective cohort study of primary total knee arthroplasties performed from 2001 to 2009 was conducted with use of a community total joint replacement registry. Patient characteristics and procedure details were identified. Cox regression models were used. Bearing type was investigated as a risk factor for revision while adjusted for other risk factors such as age, American Society of Anesthesiologists (ASA) score, body mass index, sex, race, diagnosis, bilateral procedures, cruciate-retaining versus posterior-stabilized components, surgical approach, fixation, patellar resurfacing, hospital and surgeon volumes, and fellowship training.
The study cohort consisted of 47,339 total knee arthroplasties, with 62.6% of the procedures in women. Fixed bearings were used in 41,908 knees (88.5%) and mobile bearings in 4830 (10.2%). Rotating-platform designs were used in all mobile-bearing total knee arthroplasties (3112 had a Rotating-Platform Press-Fit Condylar posterior-stabilized design; 1053, a Low Contact Stress [LCS] design; and 665, a Rotating-Platform Press-Fit Condylar cruciate-retaining design). Patients who received fixed-bearing total knee arthroplasty systems were older (mean age, 68.1 years) than those who received mobile-bearing total knee arthroplasty systems (mean age, 62.2 years); the difference was significant (p < 0.001). Overall, 515 knees (1.1%) were revised for reasons other than infection. The survival rate was 97.8% (95% confidence interval [CI], 97.4% to 98.0%) at 6.7 years. The adjusted risk of aseptic revision for the LCS total knee replacements was 2.01 times (95% CI, 1.41 to 2.86) higher than that for fixed-bearing total knee replacements (p < 0.001).There was no significant revision risk for the other mobile-bearing total knee arthroplasty systems. There was no association with surgeon and hospital case volumes and the risk of revision total knee arthroplasty.
Our study suggests the benefit of potential long-term wear reduction with the LCS implant may not be realized in a community-based setting, where a variety of surgical skills, surgical experience, and diverse patient demographic factors may affect early outcomes.
Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.
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ABSTRACT: Mobile-bearing total knee prostheses were designed to reduce wear and improve implant survivorship following total knee arthroplasty. However, the benefit of mobile-bearing total knee arthroplasty remains unproven. Both mobile-bearing and fixed-bearing total knee arthroplasty implants are available in posterior-stabilized and non-posterior-stabilized designs. With the latter, the implant does not recreate the function of the posterior cruciate ligament (PCL) with a posterior-stabilizing cam mechanism. The purpose of the present study was to compare mobile-bearing, non-posterior-stabilized devices with fixed-bearing, non-posterior-stabilized devices used in total knee arthroplasty through a novel multinational study design. Through the use of a distributed health data network, primary total knee arthroplasties performed for osteoarthritis from 2001 to 2010 were identified from six national and regional total joint arthroplasty registries. Multivariate meta-analysis was performed with use of linear mixed models, with the primary outcome of interest being revision for any reason. Survival probabilities and their standard errors were extracted from each registry for each unique combination of the covariates. A total of 319,616 patients (60% female) underwent non-posterior-stabilized total knee arthroplasty. A fixed-bearing, non-posterior-stabilized design was used in 258,190 (81%) of the knees and a mobile-bearing, non-posterior-stabilized design in 61,426 (19%) of the knees. Sixty-nine percent of the patients who received a fixed-bearing implant were over sixty-five years of age, compared with 63% of those who received a mobile-bearing implant. Mobile-bearing designs had a higher risk of revision, with a hazard ratio of 1.43 (95% confidence interval, 1.36 to 1.51; p < 0.001). Previous comparisons of mobile-bearing and fixed-bearing total knee arthroplasty outcomes have been inconclusive. The current study utilized an advanced, harmonized distributed analysis of six national and regional joint-replacement registries. To our knowledge, it is the largest analysis of mobile-bearing total knee arthroplasty to date. Mobile-bearing, non-posterior-stabilized designs presented a greater risk of failure than was found for fixed-bearing, non-posterior-stabilized designs. Caution should be used in the selection of the mobile-bearing non-posterior-stabilized design for total knee replacement. Copyright © 2014 by The Journal of Bone and Joint Surgery, Incorporated.The Journal of Bone and Joint Surgery 12/2014; 96(Supplement 1):52-58. DOI:10.2106/JBJS.N.00466 · 4.31 Impact Factor
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ABSTRACT: Posterior-stabilized total knee prostheses were introduced to address instability secondary to loss of posterior cruciate ligament function, and they have either fixed or mobile bearings. Mobile bearings were developed to improve the function and longevity of total knee prostheses. In this study, the International Consortium of Orthopaedic Registries used a distributed health data network to study a large cohort of posterior-stabilized prostheses to determine if the outcome of a posterior-stabilized total knee prosthesis differs depending on whether it has a fixed or mobile-bearing design. Aggregated registry data were collected with a distributed health data network that was developed by the International Consortium of Orthopaedic Registries to reduce barriers to participation (e.g., security, proprietary, legal, and privacy issues) that have the potential to occur with the alternate centralized data warehouse approach. A distributed health data network is a decentralized model that allows secure storage and analysis of data from different registries. Each registry provided data on mobile and fixed-bearing posterior-stabilized prostheses implanted between 2001 and 2010. Only prostheses associated with primary total knee arthroplasties performed for the treatment of osteoarthritis were included. Prostheses with all types of fixation were included except for those with the rarely used reverse hybrid (cementless tibial and cemented femoral components) fixation. The use of patellar resurfacing was reported. The outcome of interest was time to first revision (for any reason). Multivariate meta-analysis was performed with linear mixed models with survival probability as the unit of analysis. This study includes 137,616 posterior-stabilized knee prostheses; 62% were in female patients, and 17.6% had a mobile bearing. The results of the fixed-effects model indicate that in the first year the mobile-bearing posterior-stabilized prostheses had a significantly higher hazard ratio (1.86) than did the fixed-bearing posterior-stabilized prostheses (95% confidence interval, 1.28 to 2.7; p = 0.001). For all other time intervals, the mobile-bearing posterior-stabilized prostheses had higher hazard ratios; however, these differences were not significant. Mobile-bearing posterior-stabilized prostheses had an increased rate of revision compared with fixed-bearing posterior-stabilized prostheses. This difference was evident in the first year. Copyright © 2014 by The Journal of Bone and Joint Surgery, Incorporated.The Journal of Bone and Joint Surgery 12/2014; 96(Supplement 1):59-64. DOI:10.2106/JBJS.N.00556 · 4.31 Impact Factor
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ABSTRACT: In the late 1990s, new developments in knee replacement were identified as a priority for research within the NHS. The newer forms of arthroplasty were more expensive and information was needed on their safety and cost-effectiveness. The Knee Arthroplasty Trial examined the clinical effectiveness and cost-effectiveness of four aspects of knee replacement surgery: patellar resurfacing, mobile bearings, all-polyethylene tibial components and unicompartmental replacement. This study comprised a partial factorial, pragmatic, multicentre randomised controlled trial with a trial-based cost-utility analysis which was conducted from the perspective of the NHS and the patients treated. Allocation was computer generated in a 1 : 1 ratio using a central system, stratified by eligible comparisons and surgeon, minimised by participant age, gender and site of disease. Surgeons were not blinded to allocated procedures. Participants were unblinded if they requested to know the prosthesis they received. The setting for the trial was UK secondary care. Patients were eligible for inclusion if a decision had been made for them to have primary knee replacement surgery. Patients were recruited to comparisons for which the surgeon was in equipoise about which type of operation was most suitable. Patients were randomised to receive a knee replacement with the following: patellar resurfacing or no patellar resurfacing irrespective of the design of the prosthesis used; a mobile bearing between the tibial and femoral components or a bearing fixed to the tibial component; a tibial component made of either only high-density polyethylene ('all polyethylene') or a polyethylene bearing fixed to a metal backing plate with attached stem; or unicompartmental or total knee replacement. The primary outcome was the Oxford Knee Score (OKS). Other outcomes were Short Form 12; EuroQol 5D; intraoperative and postoperative complications; additional surgery; cost; and cost-effectiveness. Patients were followed up for a median of 10 years; the economic evaluation took a 10-year time horizon, discounting costs and quality-adjusted life-years (QALYs) at 3.5% per annum. A total of 116 surgeons in 34 centres participated and 2352 participants were randomised: 1715 in patellar resurfacing; 539 in mobile bearing; 409 in all-polyethylene tibial component; and 34 in the unicompartmental comparisons. Of those randomised, 345 were randomised to two comparisons. We can be more than 95% confident that patellar resurfacing is cost-effective, despite there being no significant difference in clinical outcomes, because of increased QALYs [0.187; 95% confidence interval (CI) -0.025 to 0.399] and reduced costs (-£104; 95% CI -£630 to £423). We found no definite advantage or disadvantage of mobile bearings in OKS, quality of life, reoperation and revision rates or cost-effectiveness. We found improved functional results for metal-backed tibias: complication, reoperation and revision rates were similar. The metal-backed tibia was cost-effective (particularly in the elderly), costing £35 per QALY gained. The results provide evidence to support the routine resurfacing of the patella and the use of metal-backed tibial components even in the elderly. Further follow-up is required to assess the stability of these findings over time and to inform the decision between mobile and fixed bearings. Current Controlled Trials ISRCTN45837371. This project was funded by the NIHR Health Technology Assessment programme and the orthopaedic industry. It will be published in full in Health Technology Assessment; Vol. 18, No. 19. See the NIHR Journals Library website for further project information.03/2014; 18(19):1-236. DOI:10.3310/hta18190