Background. No study compared the clinical results of the posterior-stabilized mobile-bearing knee with those of nonposterior-stabilized mobile-bearing knee in the same patients. The purpose of this study was to examine whether the clinical and radiographic results, range of motion, patients satisfaction, and complication rates would be better in the knees with a posterior-stabilized mobile-bearing knee than in the knees with a nonposterior-stabilized mobile-bearing knee. Methods. One hundred and fourteen patients (mean age, 67.9 years) received a nonposterior-stabilized mobile-bearing knee prosthesis in one knee and a posterior-stabilized mobile-bearing knee prosthesis in the contralateral knee. Seven patients were men, and 107 were women. At the time of each follow-up (mean, 7.3 years; range, seven to 7.6 years), the patients were assessed clinically and radiographically. Results. The mean postoperative Knee Society knee score (95 points versus 96 points, p=0.176), Hospital for Special Surgery knee score (92 points versus 93 points, p=0.077), and Western Ontario and McMaster University Osteoarthritis score (21 versus 20 points, p=0.785) were similar between the two group. At the final follow-up, the average range of motion was 27.7° (range, 70° to 150°) in the knees with a nonposterior stabilized mobile-bearing prosthesis and it was 132° (range, 90 to 150 °) in the knees with a posterior-stabilized mobile-bearing prosthesis. Complication rates (2.6% versus 1.8%) were similar between the two groups. The estimated survival rate was 97.4% at eight years with an overall revision rate of 2.6% (three of 114 knees) in the nonposterior-stabilized mobile-bearing prosthesis group and 98.2% at eight years with an overall revision rate of 1.8% (two of 114 knees) in the posterior-stabilized mobile-bearing prosthesis group. Conclusions. After a minimum duration of follow-up of seven years, we found no significant differences between the two groups with regard to the clinical and radiographic results, or patient satisfaction, or complication rate. However, the posterior-stabilized mobile-bearing prosthesis group had a greater range of knee motion than the nonposterior-stabilized mobile-bearing prosthesis group

The Low Contact Stress (LCS) mobile-bearing total knee replacement (TKR) was designed to minimize polyethylene wear, aseptic loosening and osteolysis. However, registry data suggests there is a significantly greater revision rate associated with the LCS TKR. The primary aim of this study was to assess long-term survivorship of the LCS implant. Secondary aims were to assess survival according to mechanism of failure and identify predictors of revision. We retrospectively identified 1091 LCS TKRs that were performed between 1993 and 2006. There was incomplete data available 33 who were excluded. The mean age of the cohort was 69 (SD 9.2) years and there were 577 TKRs performed in females and 481 in males. Mean follow up was 14 years (SD 4.3). There were 59 revisions during the study period: 14 for infection, 18 for instability, and 27 for polyethylene wear. 392 patients died during follow up. All cause survival at 10-year was 95% (95%CI 91.7–98.3) and at 15-year was 93% (95%CI 88.6–97.8). Survival at 10-years according to mechanism of failure was: infection 99% (95%CI 94–100%), instability 98% (95%CI 94–100%), and polyethylene wear 98% (95%CI92–100). Of the 27 with polyethylene wear only 19 had associated osteolysis requiring component revision, the other 8 had simple polyethylene exchanges. Cox regression analysis, adjusting for confounding variables, identified younger age was the only predictor of revision (hazard ratio 0.96, 95%CI 0.94–0.99, p=0.003). The LCS TKR demonstrates excellent long-term survivorship with a low rate of revision for osteolysis, however the risk is increased in younger patients