Functional outcome and range of motion of high-flexion posterior cruciate-retaining and high-flexion posterior cruciate-substituting total knee prostheses. A prospective, randomized study.

BACKGROUND: Although the design features of the high-flexion posterior cruciate-retaining and high-flexion posterior cruciate-substituting total knee prostheses reportedly improve the range of knee motion, a clinical comparison of both systems with regard to range of motion has not been reported, to our knowledge. The purpose of the present study was to compare the range of motion and functional outcome in knees receiving either a high-flexion posterior cruciate-retaining or a high-flexion posterior cruciate-substituting total knee prosthesis.

METHODS: Two hundred and fifty patients (mean age, 71.6 years) received a high-flexion posterior cruciate-retaining total knee prosthesis in one knee and a high-flexion posterior cruciate-substituting total knee prosthesis in the contralateral knee. Ten patients were men, and 240 were women. At the time of each follow-up (minimum duration of follow-up, two years; mean, 2.3 years), the patients were assessed clinically and radiographically with use of the knee-rating systems of the Knee Society and the Hospital for Special Surgery. In addition, each patient completed the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) questionnaire. Non-weight-bearing and weight-bearing ranges of knee motion were determined in both groups.

RESULTS: The mean postoperative Knee Society knee score was 94 points for the knees treated with a high-flexion cruciate-retaining prosthesis and 95 points for those treated with a high-flexion posterior cruciate-substituting prosthesis. The mean postoperative Hospital for Special Surgery knee score was 90 points for the knees that had been treated with a high-flexion posterior cruciate-retaining prosthesis and 91 points for those that had been treated with the high-flexion posterior cruciate-substituting prosthesis. At the time of the latest follow-up, the knees that had been treated with a high-flexion posterior cruciate-retaining prosthesis had a mean non-weight-bearing range of motion of 133 degrees and a mean weight-bearing range of motion of 118 degrees. The knees that had been treated with a high-flexion posterior cruciate-substituting prosthesis had a mean non-weight-bearing range of motion of 135 degrees and a mean weight-bearing range of motion of 122 degrees. No knee had aseptic loosening, revision, or osteolysis.

CONCLUSIONS: After a minimum duration of follow-up of two years, there was no difference in range of motion or clinical and radiographic results between knees that had received a high-flexion posterior cruciate-retaining total knee prosthesis and those that had received a high-flexion posterior cruciate-substituting total knee prosthesis.