Preservation of femoral bone mass after total hip replacements with a lateral flare stem.

Uncemented, porous-coated femoral stems rely on bone in-growth to achieve stable, long-lasting fixation. The loss of proximal femoral bone mass around hip stems has been traditionally termed "stress shielding" and has been linked to the transfer of loads to the diaphysis and the relative unloading of the proximal femur. A total of 10 total hip arthroplasties with a proximally coated lateral flare device designed to engage both cortices at the metaphyseal level were evaluated with dual-energy X-ray (DEXA) absorptiometry and qualitative radiographic changes 3 weeks after surgery and at 12, 24 and 52 weeks thereafter. All hips were radiologically stable. The DEXA measurements revealed an overall increase in the bone mineral density (BMD) at 52 weeks of 3%. Greater gains were observed at or below the lateral flare of the stem in the metaphyseal femur.