OBJECTIVETo evaluate the changes of periprosthetic bone mineral density in femur after hip resurfacing arthroplasty.

METHODSFrom July 2002 to June 2005, a comparative study was carried out on 52 hips in 52 patients. Twenty-six patients (26 hips) who underwent Birmingham hip resurfacing arthroplasty (group BHR), and 26 patients (26 hips) who performed cementless total hip arthroplasty with Versys System stem (group THA). The periprosthetic bone mineral density of the femur was measured through dual energy X-ray absorptiometry of the Gruen zones at pre-operation, post-operation 3, 6, 12 and 24 months in patients from both group BHR and group THA. The bone mineral density of femoral neck in group BHR was measured too. Changes of bone mineral density ratio in proximal femur between pre-operation and post-operation were compared and analyzed.

RESULTSThe mean ratio of bone mineral density of the proximal femur in group BHR reduced by 5.8%, 4.9%, 2.6% and 0.4%, in group THA reduced by 7.0%, 10.6%, 1.0% and 4.1% at 3, 6, 12 and 24 months respectively. In group BHR, the mean ratio of bone mineral density in range of interest 1 decreased to 89.7% at 6 months and increased to 103.8% at 24 months, in range of interest 7 decreased to 95.1% at 6 months and increased to 103.7% at 24 months. In group THA, the mean ratio of bone mineral density in range of interest 1 decreased to 90.8% at 6 months, 94.4% at 24 months and in range of interest 7 decreased to 94.2% at 3 months, 96.7% at 24 months. In group BHR, the bone mineral density of femoral neck was restored to the pre-operation level at 6 months. The bone mineral density in superior-lateral zone of femoral neck decreased to 97.1% at 3 months and increased to 107.4% at 24 months respectively. The bone mineral density in inferior-medial zone of femoral neck increased to 117.9% at 24 months.

CONCLUSIONThe bone stock of proximal femur can be well preserved and recovered quickly after hip resurfacing arthroplasty.