Biomechanical properties of human os calcanei: relationships with bone density and fractal evaluation of bone microarchitecture

The relationship between bone strength and bone mass is well established. The link between trabecular microarchitecture and biomechanical properties has been less extensively explored. To address this question, we have tested the mechanical behaviour of calcaneus bone samples and investigated the correlations between mechanical properties on the one hand, bone density and fractal analysis of microarchitecture on the other hand. Mechanical properties of 43 human os calcanei were determined by uniaxial compression testing of samples from tuber calcanei. Ash density, bulk density and dual energy X-ray absorptiometry of the samples were measured. Fractal analysis of the trabecular bone on calcaneus radiographs was performed by two estimators derived from the fractional Brownian motion model. The mechanical properties of human os calcis were found to correlate with age and density measurements. Fractal parameters derived from the bone texture analysis showed weaker but significant correlations with bone strength. Fractal analysis of texture could account in part for the variations of bone strength, but in this study cannot explain better than density the mechanical properties of trabecular bone. Nevertheless, it provides a non-invasive means of assessing molecular bone microarchitecture.