Comparison of the low contact stress and press fit condylar rotating-platform mobile-bearing prostheses in total knee arthroplasty: a prospective randomized study.

BACKGROUND: To our knowledge, no study to date has compared the clinical results of posterior cruciate-sacrificing mobile-bearing total knee replacements with those of posterior-stabilized mobile-bearing total knee replacements in the same patients. The purpose of the present study was to compare the clinical and radiographic results of these two designs. We hypothesized that the results would be better for knees treated with the posterior-stabilized mobile-bearing prosthesis.

METHODS: The present study consisted of a consecutive series of 107 female patients (mean age, 66.8 years) who underwent bilateral simultaneous total knee arthroplasty at the same surgical setting. All of these patients received a posterior cruciate-sacrificing mobile-bearing prosthesis in one knee and a posterior-stabilized mobile-bearing prosthesis in the contralateral knee. At the time of each follow-up (mean, 7.4 years; range, seven to 7.6 years), the patients were assessed clinically.

RESULTS: The mean postoperative Knee Society knee score (96 compared with 97 points) and Hospital for Special Surgery knee score (93 compared with 94 points) were similar between the two groups. At the time of the latest follow-up, the average range of motion was 127.7° (range, 70° to 150°) in the knees with a posterior cruciate-sacrificing mobile-bearing prosthesis and 132.4° (range, 90° to 150°) in the knees with a posterior-stabilized mobile-bearing prosthesis. With a margin of error of the manual measurement of 5°, this difference was not significant. The estimated survival rate was 97.2% (95% confidence interval, 91% to 99%) at seven years in the posterior-cruciate sacrificing mobile-bearing prosthesis group and 98.1% (95% confidence interval, 92% to 99%) at seven years 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, including knee range of motion.