Results of total hip arthroplasty with bone graft and support ring for protrusio acetabuli in rheumatoid arthritis

We evaluated 19 hips of 15 rheumatoid arthritis patients with protrusio acetabuli that had been surgically treated with total hip arthroplasty (THA) using a support ring; four hips were replaced with a TACT cup supporter, one hip with a Kerboull plate, six hips with a Ganz ring, and eight hips with a Müller ring. The average age was 60.2 years (range 48–75 years), and the average follow-up was 38 months (range 6–74 months). Two patients (three hips) died before the final follow-up, and two patients (two hips) underwent revision owing to loosening of the Ganz ring. Hip functions were rated according to the evaluation chart of hip joint functions of the Japanese Orthopaedic Association (JOA score). The mean total JOA score was 25.2 ± 8.6 preoperatively and 55.6 ± 8.7 postoperatively. Radiographically, 17 hips (minus the two revised hips) showed satisfactory incorporation of bone graft and no loosening of the support ring. The mean depth of protrusio acetabuli for these 17 hips was 3.5 ± 4.1mm before operation, 2.8 ± 5.1mm just after operation, and 2.3 ± 3.9mm at the final follow-up (no significant difference at the critical rate of 5%). Our study indicated the usefulness of THAs using a bone graft and a support ring in RA patients with protrusio acetabuli.