EFFECTS OF ALENDRONATE, HORMONE REPLACEMENT THERAPY AND COMBINATION TREATMENT ON HIP STRUCTURAL GEOMETRY IN OLDER WOMEN: A HIP STRUCTURE ANALYSIS- BASED RANDOMIZED CONTROLLED TRIAL

Background: The antiresorptive therapy can only partially explain the reduction in the fracture risk by augmenting the bone mineral density (BMD). Structural geometry is also an important factor in bone strength and it cannot be sufficiently measured alone with BMD. Purpose: To assess the impact of alendronate (ALN), hormone replacement therapy (HRT) and a combination of the two on the hip structural geometry through hip structure analysis (HSA). Methods: HSA was reanalyzed (in 76 older women) with the use of the dual-energy X-ray absorptiometry scan in a randomized, double-blind, placebo controlled trial followed up over a 3 year period. The HSA measurements of the cross-sectional area, cortical thickness, section modulus, and BMD of the femur neck were evaluated. Findings: There were no differences in baseline characteristics. The active treatments yielded great improvements on majority of the structural indices as compared to placebo. Combination therapy showed the highest increases of cross-sectional area, cortical thickness, section modulus and BMD by HSA, intermediary effects of ALN and minor yet significant effects by HRT. Conclusion: Antiresorptive therapy, and specifically a combination therapy, has a significant improvement in the geometry of the hip structure indicating an improvement in mechanical strength going beyond simple alteration in the BMD.