Gender differences in trabecular bone architecture of the distal radius assessed with magnetic resonance imaging and implications for mechanical competence.

High-resolution magnetic resonance imaging (hrMRI) has recently made it possible to evaluate trabecular bone structure in vivo. Despite obvious gender differences in fracture incidence at the distal radius, little is known about gender differences in trabecular bone microarchitecture and its relationship to the structural strength of the forearm. The aim of this study was to determine trabecular bone structure in the distal radius of elderly women and men and its correlation with failure loads of the distal radius as determined in a fall configuration. Specifically, we tested the hypotheses that structural indices differ between women and men and that they offer information that is independent from BMD for predicting structural strength. Intact right arms were obtained from 73 formalin-fixed cadavers (age 80+/-11 years, 43 women, 30 men). Trabecular structural indices (apparent bone volume fraction [app. BV/TV], trabecular number [app. Tb.N], trabecular separation [app. Tb.Sp], trabecular thickness [app. Tb.Th] and fractal dimension [Frac.Dim]) were assessed in the distal metaphysis, using hrMRI with 156 microm in-plane resolution and proprietary digital image analysis, while BMD was measured with dual X-ray absorptiometry (DXA). Women displayed significantly lower BMD (-29.8%, p <0.001), app. BV/TV (-8.2%, p <0.05) and app. Tb.Th (-10.2%, p <0.001) than men, whereas app. Tb.N, app. Tb.Sp. and fractal dimension did not differ significantly. Structural parameters differed between normal and osteopenic women (BV/TV: -11%, p <0.01; Tb.Th: -8%, p <0.001) and between normal and osteoporotic women BV/TV: -21%, p <0.001; Tb.Th: -16%, p <0.001). App. BV/TV, app. Tb.Th and fractal dimension provided information independent from BMD in the prediction of radial failure loads in multiple regression models. These findings imply that it should be of clinical interest to monitor both bone mass and trabecular microstructure for predicting osteoporotic fracture risk.