Changes in proximal femoral bone mineral density around a hydroxyapatite-coated hip joint arthroplasty

Abstract

Objective. To present the results of a prospective analysis of proximal femoral bone mineral density changes around a hydroxyapatite-coated total hip joint replacement. Methods. 14 patients with osteoarthritis of the hip were enrolled in the study and treated with an uncemented ABG prosthesis. Dual energy x-ray absorptiometry scanning was performed in 9 patients preoperatively, and at 3, 6, 12, and 24 months postoperatively. An orthopaedic software program was used to determine the bone mineral density in the proximal femur, expressed as a percentage of the preoperative value. Results. The values of Gruen zones 1 to 6 averaged between 96.0% and 113.8% of the preoperative value by 24 months (overall average, 104.1%). In zone 7, however, there was a gradual decline in bone mineral density to an average of 72.1% of the preoperative value by 24 months. This represented ongoing loss of bone from the calcar; although this may not pose a problem to the prosthetic's short-term stability, it may render potential revision surgery more difficult. Conclusion. The initial outcome of uncemented total hip replacement appears to be promising. There was excellent maintenance of bone around the femoral component in all regions other than the calcar and lesser trochanter. Further scans are required to see if these trends continue in the long term.