Determination of femur structural properties by geometric and material variables as a function of body weight in rats. Evidence of a sexual dimorphism.

Femur diaphyses of male and female Wistar rats were densitometrically and biomechanically assayed. The BMD-dependent material properties were better in female than in male bones, but cross-section geometric properties were better in male femurs. As a result, mechanical properties of the integrated diaphyses were better in males, but differences disappeared after statistical adjustment of data to a common body weight. Results evidence a feed-back mechanism locally controlling the strain-dependent bone modelling and the corresponding cross-sectional design as related to bone stiffness, with a set-point adjusted to animal biomass. A sexual dimorphism of bone biomechanics is also described for the species.