Objective. This study analyzed the midterm results of hip resurfacing arthroplasty in patients with rheumatoid arthritis.
Methods. Between October of 2003 and September of 2008, 13 consecutive hips that were treated with hip resurfacing arthroplasty due to rheumatoid arthritis were analyzed. The average follow up period was 48.6 months and the mean age at the time of operation was 35.9 years old. The mean BMI at the operation was 23.2 kg/m². The implanted prostheses were the Conserve Plus system in five hips, the Birmingham hip resurfacing system in four hips and the Durom system in four hips. The results were clinically evaluated with the Harris hip score, the UCLA activity score, hip or thigh pain, the limb length discrepancy and the range of motion. As radiological evaluation, we observed the patterns of bone remodeling and complications such as femoral neck fracture, loosening and osteolysis.
Results. The average Harris hip score improved from 62.2 to 98.9 at the final visit. The range of motion improved to 0^o in flexion contracture, 118.1^o in further flexion, 22.7^o in internal rotation, 40.4^o in external rotation, 28.8^o in adduction and 38.1^o in abduction, respectively. No patient complained of a limb length discrepancy and hip or thigh pain. Radiographically, impingement between the acetabular component and the femoral neck was observed in one case. However, radiographic findings such as osteolysis, radiolucency, wear and loosening were not observed.
Conclusion. The midterm results of hip resurfacing arthroplasty in patients with rheumatoid arthritis were excellent. But long-term studies are needed to determine the survivorship and to evaluate the osteoporotic change, the metal ion level and their influence after hip resurfacing arthroplasty.

Keywords: Rheumatoid arthritis, Hip resurfacing arthroplasty