Effects of postoperative weight-bearing on body composition and bone mineral density after uncemented total hip arthroplasty.

OBJECTIVE To investigate whether a postoperative weight-bearing regimen affects changes in bone mineral density and body composition after uncemented total hip arthroplasty, and to investigate the changes over a 5-year period after the surgical procedure. DESIGN Secondary analysis of a previous randomized controlled trial. METHODS A total of 39 patients were randomized to immediate full weight-bearing or partial weight-bearing for 3 months. Dual-energy X-ray absorptiometry was used to measure bone mineral density of the contralateral hip and both heels and to measure body composition. RESULTS The weight-bearing regimen had no effect on change in bone mineral density or body composition after 3 and 12 months. At 5 years, there was a decrease in bone mineral density of 3% in the total body and 2-3% in the contralateral hip regions. At 5 years we found a decrease in total body bone mineral content of 5%, but no changes in fat mass or lean mass compared with preoperative values. CONCLUSION The postoperative weight-bearing regimen had no effect on changes in body composition or bone mineral density. Five years after total hip arthroplasty there was a decrease in bone mineral content and bone mineral density, but no changes in lean mass or fat mass.