Bone mineral density of the proximal femur recovers after metal-on-metal hip resurfacing

Bone resorption of the proximal femur is a frequent complication of total hip replacement. As hip resurfacing (HR) may load the bone more physiologically, we measured proximal femur bone mineral density (BMD) in 21 patients with HR. DEXA analysis was performed in the 7 Gruen zones and in the femoral neck pre-operatively and at 3, 9, and 24-months post-operatively. In Gruen zone-2 the BMD ratio decreased to 90+/-18.8% (p=0.0009) at 3months and completely restored at 24-months to 100+/-17.7% (p=0.01). In Gruen zone-7 the BMD ratio decreased to 93+/-15.3% (p=0.05) by 3 months and surpassed the baseline to 105+/-14.8% (p=0.01) at 24-months. A positive correlation was observed between valgus positioning of the femoral component and BMD in Gruen zone-2 and 7 respectively. HR preserves the bone-stock of the proximal femur. When the femoral component is implanted in a valgus position BMD is further enhanced, thus potentially reducing the risk of femoral neck fractures.