Effect of disuse on bone mineral content,lean mass,and fat mass in osteoarthritic patients

Purpose: To evaluate the effect of disuse on bone mineral content (BMC), lean mass, and fat mass.Method and subjects: We obtained BMC, lean mass, and fat mass from measurements of each side of the arm and the leg in 20 women with unilateral hip osteoarthritis and 63 normal women using a whole-body dual-energy X-ray absorptiometry (DXA) scan. The ratio of the affected side to the unaffected side (A-U ratio) was calculated for BMC, lean mass, and fat mass in the arm and the leg.Results: A significant intergroup difference in the A-U ratio was noted for leg BMC (0.85vs 0.99,P<0.01), and for lean mass of the leg (0.88vs 0.99,P<0.01). When leg BMC was adjusted with lean mass, this intergroup difference became insignificant.Conclusion: This study reconfirmed that a decrease in BMC and lean mass can result from disuse. We suggest that a large portion of BMC loss in the immobilized leg might be a secondary change resulting from lean mass loss.