From 1972 to 1981, 75 total hip replacements were performed on 56 patients with rheumatoid arthritis in our department. Eleven patients had definite RA and the other 45 had classical RA, according to the criteria of the American Rheumatism Association. The age at operation was 27 to 68 years (average, 51 years), and the average duration of the disease was 13 years. A Charnley type prosthesis was used in 41 hips and a Charnley-Muller type in 34 hips, including 19 replacements with a cup supporter. Setting the cup in the proper position was very difficult, especially in the cases with protrusio acetabuli (PA). A cup supporter was, therefore, devised in our clinic to get a good cup setting by combining the supporter with the Charnley-Muller type prosthesis. Assessment of the patients' movement was carried out by a method described by Fujibayashi and others. Twenty-three patients improved within 2 years of the operation, but poor results were found in patients with knee destruction and complications such as deep infection (1 case) and prosthesis loosening (1 cases). Destruction of the rheumatoid hip was studied roentgenographically. Pathology of the excised femoral head and synovium was compared with the X-ray findings in relation to drug therapy. Preoperative X-ray examination, according to criteria of Uchida et al. (1978), showed the atrophic type in 44 percent and PA in 38 percent. Incidence of protrusio was significantly high in patients with systemic steroid intake. Adrenal cortical steroids may play an important role in the progress of the protrusion in rheumatoid patients. However, there was shown no correlation among hip destruction and age, duration of RA, the severity of joint inflammation and the use of gold or D-penicillamine.
In a Pathological study of 35 excised femoral heads, cyst formation and periarticular osteophytes in the remaining head contour were found mainly in the protrusio type. Repair of fibrocartilaginous tissue was observed both in the protrusio and collapse type of acetabulum, but clinically, no significant improvement was detected in such cases.