Different cup migration in rheumatoid arthritis and arthrosis - A radiographic analysis of 127 uncemented acetabular cups

We compared retrospectively the radiographic migration profiles of 82 aceta bular components in 61 patients having rheumatoid arthritis with those of 4 5 hips having arthrosis who underwent a standardized technique of cementles s arthroplasty with the Zweymuller prosthesis (Alloclassic(R)). We used a m odification of Dickob's technique of digital migration analysis that correc ts for magnification errors and horizontal pelvic tilt. The rheumatoid pati ents were stratified as having oligoarticular, polyarticular, or mutilating arthritis. The overall rate of acetabular loosening in rheumatoid hips aft er mean 88 (26-117) months was 4%. Loosening was seen only in cases with mu tilating arthritis and acetabular protrusion, where the direction of cup mi gration was also clearly different from that detected in the other types of rheumatoid arthritis and in arthrosis. The different patterns of cup migration in cementless hip replacement for r heumatoid arthritis, depending on disease severity, is of importance when c omparing outcome of total hip arthroplasty in rheumatoid patients.