One hundred and twenty-nine patients who had had 153 consecutive primary total knee replacements (twenty-four bilateral procedures) between February 1988 and February 1990, with insertion of medial pivot total knee system with cementless femoral and cementless tibial component without replacement of the patella, were enrolled in a prospective study. The average age of the patients at the time of surgery was 67.4 years, the average weight was 78 kg, and the most common diagnosis was osteoarthritis (prevalence, 92.9%). Twenty-six knees had a valgus deformity, ninrty-nine had a varus deformity, and twenty-eight had a normal alignment of 5 to 10 degrees of valgus Six patients had a previous high tibial osteotomy, twenty-one arthroscopic debridment and thirty-two total knee athroplasty at the other knee.

One hundred and ten patients (123 knees) were followed for an adequate interval (mean, 5.1 years; range, 3.8 to 6.8 years). Thirteen patients (fifteen knees) died, and twelve patients (fifteen knees) were lost to follow-up. The mean age of the patients at the time of the index arthroplasty was seventy years (range, twenty-nine to eighty-five years). The patients were evaluated clinically and radiographically, according to the scoring system of the Knee Society, and the results on a self-administered questionnaire were used to evaluate pain, function, satisfaction, and patellofemoral symptoms. A Kaplan-Meier survivorship analysis was performed with a revision operation as the end point. Failure was defined as aseptic loosening as evidenced by progressive radiolucent lines and/or revision due to aseptic loosening or collapse.

The mean functional and clinical scores, according to the system of the Knee Society, were 85 and 93 points, respectively, at the most recent follow-up examination. The result was excellent for 103 knees, good for thirteen, fair for three, and poor for six. One revision operation was necessary because of infection. The over-all rate of patellofemoral symptoms was 6 per cent (seven knees). Non-progressive radiolucent lines were present at the cement-bone interface in 39 per cent (thirty-nine) of the ninety-nine knees that had complete radiographic follow-up. No prosthesis had loosened by the time of the most recent follow-up examination. The rate of survival of the implant was 97 per cent at six years, and the standard error of the mean was 1.6 per cent.

In the present series, total knee arthroplasties with the medial pivot modular knee system resulted in excellent relief of pain, an excellent range of motion, and restoration of function. They were also associated with a low prevalence of patellofemoral problems.