Studies of crystal orientation and calcium distribution in trabecular bone

These studies were focused on the relation between the orientation of crystallites, calcium concentrations and the stress distributions within human vertebral bodies. The elemental composition was measured using the proton induced X-ray emission method in combination with a proton microprobe (micro-PIXE) while the orientation of the hydroxyapatite crystals was extracted from the X-ray diffraction spectra acquired during the synchrotron microprobe irradiation (micro-XRD). To calculate the distribution of stresses the finite element (FE) method was applied. The distributions of Ca concentrations indicate that the irradiated samples differ slightly in the degree of mineralization. The micro-XRD data confirmed that c-axes of the hydroxyapatite crystallites are preferentially oriented ((40-80)% of the crystals are textured). The comparison of the micro-XRD data and the results of the FE calculations proved the hypothesis that the preferential orientation of crystals reflects the mechanical loading of the structure.