[Cementless hip prosthesis in patients with rheumatoid arthritis]

From 1986 to 1996, we implanted a total of 92 hip arthroplasties (86 cementless, 4 hybrid and 2 cemented) in 65 patients with rheumatoid arthritis. Of the 89 uncemented cups, 59 were threaded cups (Hofer-Imhof n = 45, Zweymüller n = 7, Mecring n = 5, PM n = 2) and 30 were hemispherical cups of the Harris Galante type I and II. 87 stems were implanted without cement (Zweymüller SL n = 58, Uni n = 16, Schenker n = 9, Zweymüller I n = 4) and 5 with cement. One patient died postoperatively and three (4 implants) within the first year. To date, one cup of each threaded type had to be revised because of loosening (revision rate approx. 6.8%); Up to now, three of 87 (approx. 3.4%) stem revisions (1 x Zweymüller I, 1 x Schenker, 1 x Zweymüller SL) have been undertaken. Ten patients with twelve hip arthroplasties did not return for follow-up; some of them had a poor general health status. The clinical and radiological results of the arthroplasties of 52 patients showed a Harris Hip Score averaging 72 after an average of 54 months (min. 12-max. 132). Ten patients had minor complaints in the hip region. 79% of the uncemented implants (70 out of 89 cups, 69 out of 87 stems) were assessed radiologically. Two threaded cups showed slight migration after cancellous bone grafting in the presence of acetabular protrusion that was present in a total of 13 hip joints. This subsided markedly after filling with cancellous bone and recentering of the hip joint. Homogeneous incorporation of the bone grafting und thus remodelling of the medial wall was achieved, with the bone graft exhibiting marked reduction. At final follow-up, approx. 75% of the cementless cups had complete bone ingrowth without any evidence of radiolucency (type I), approx. 19% had near-complete bone ingrowth with minimal radiolucencies in one zone or in a maximum of 50% of the bone contact area (type III) and approx. 6% had radiolucencies in more than 50% of the bone contact area (type II). The radiographic evaluation of the most frequently used stem (Zweymüller SL) showed approx. 47% with only slight remodelling of the calcar (type I), approx. 33% with moderate loss of femoral density (type II) and approx. 20% with severe bone loss and thinning of cortical bone (type III).