Changes in Bone Turnover and Bone Density after Total Hip Arthroplasty

Abstract

The purpose of this study was to relate changes in bone mineral density post-operatively around a cemented femoral prosthesis with changes in bone turnover. This might allow appropriate timing of antiresorptive therapies in the prevention of aseptic loosening. We recruited ten patients and evaluated both bone turnover, by measurement of urinary N-telopeptide of collagen type I, bone specific alkaline phosphatase and osteocalcin, and bone mineral density following total hip arthroplasty. Bone formation markers decreased significantly postoperatively (p<0.001). Bone resorption markers increased postoperatively and were maximal at 6 weeks (p<0.05). There was a 5–15% decrease in bone mineral density at the proximal femur by 6 months (p<0.01). The changes in bone mineral density confirm the pattern of reduced stress in the proximal femur. The early decrease in bone formation markers was unexpected and could relate to enoxaparin therapy. The optimal time to administer antiresorptive therapy might be 6–12 weeks post-operatively.