Bone strength influences periprosthetic bone loss after hip arthroplasty

Our primary question was whether bone strength at the time of surgery, reflected by the lumbar spine T-score and femoral cortical thickness, influences periprosthetic bone loss after a total hip arthroplasty. Using dual energy x-ray absorptiometry we preoperatively and postoperatively examined 38 consecutive patients having cementless total hip arthroplasties for their bone density. Bone strength was estimated using lumbar spine bone mineral density and the ipsilateral diaphyseal cortical thickness of the femur measured on radiographs. Periprosthetic femoral bone mineral density was measured with dual energy xray absorptiometry within I week postoperatively and at 2, 4, 6, 9, 12, and 24 months thereafter. Periprosthetic bone loss was influenced by the patient's bone strength at the time of surgery. Bone loss in the calcar femoris (as much as 54% after 2 years) was greater in patients with a low lumbar spine T-score or low femoral cortical thickness. Preoperative assessment of bone strength (ie, lumbar spine bone mineral density and femoral cortical thickness on radiographs) served as a reliable indicator in predicting the extent of periprosthetic bone loss after total hip arthroplasty. Level of Evidence: Prognostic Study, Level I (high quality prospective study-all patients were enrolled at the same point in their disease with >= 80% followup of enrolled patients). See the Guidelines for Authors for a complete description of levels of evidence.