FINITE-ELEMENT MODELING OF TRABECULAR BONE - COMPARISON WITH MECHANICAL TESTING AND DETERMINATION OF TISSUE MODULUS

We combined three techniques - mechanical testing, three-dimensional i maging, and finite-element modeling - to distinguish between the contr ibutions of architecture and tissue modulus to mechanical function in human trabecular bone. The objectives of this study were 2-fold. The f irst was to assess the accuracy of micromechanical modeling of trabecu lar bone using high-contrast x-ray images of the trabecular architectu re. The second was to combine finite-element calculations with mechani cal testing to infer an average tissue modulus for the specimen. Speci mens from five human L1 vertebrae were mechanically tested along the t hree anatomic axes. The specimens were then imaged by synchrotron x-ra y tomography, and the elastic moduli of each specimen were calculated from the tomographic image by finite-element modeling. We found that 2 3-mu m tomographic images resolved sufficient structural detail such t hat the calculated anisotropy in the elastic modulus was within the un certainties of the experimental measurements in all cases. The tissue modulus of each specimen was then estimated by comparing the calculate d mean stiffness of the specimen, averaged over the three anatomical d irections, with the experimental measurement. The absolute values of t he experimental elastic constants could be fitted, again within the un certainties of the experimental measurements, by a single tissue modul us of 6.6 GPa, which was the average tissue modulus of the five specim ens. These observations suggest that a combination of mechanical testi ng, three-dimensional imaging, and finite-element modeling might enabl e the physiological variations in tissue moduli to be determined as a function of age and gender.