Survival of knee arthroplasties for rheumatoid arthritis.

During a 15-year period, 498 primary knee arthroplasties for chronic rheumatoid and related arthritides were performed. Ninety arthroplasties where prosthetic components were added, removed or replaced were recorded as failures. Eighty-one revisions were exchange arthroplasties, eight attempted arthrodeses and one an above-the-knee amputation. Survival rates were calculated with a life table technique. The cumulative 5-year survival rate was 76 per cent for tibial hemiprostheses, 78 per cent for unicompartment prostheses, 100 per cent for tricompartment prostheses, 87 per cent for stabilized prostheses and 84 per cent for hinge prostheses. Continuous deterioration was observed in the tibial hemiprostheses. The improved surgical technique, with guide instruments and release procedures for better alignment and stability, and to some extent the improved prosthetic design may explain the good early results with tricompartment prostheses.