Fractography, mechanical and structural analysis of trabecular bone from the femoral head of human cadavers

Abstract: A lowered mineral density in the skeletal bones may indicate osteoporosis and an increased risk of fragility fractures. However, lower bone mass does not reveal the whole truth about the status of the bone quality. This thesis investigated the microstructure and mechanical properties of 14 trabecular bone plugs in order to get a comprehensive understanding of how the trabecular network changes from a mechanical perspective with increasing age. The trabecular bone plugs were harvested from the femoral head of human cadavers. Micro computed tomography was performed to measure the microstructural properties. Additionally, a destructive tensile test was applied using an ’end-cap’-technique, to obtain information about the mechanics. Finally the fracture surfaces from two samples which showed completely different mechanical properties were analysed using scanning electron microscopy, to find nano-scaled fracture features. Linear regression was used to correlate the age, microstructure and mechanical properties of the trabecular plugs. The bone volume fraction, the trabecular thickness, post-yield strains, energy, and toughness decreased with increasing age, but the tissue mineral density seems to increase. The apparent modulus was positively correlated to the bone volume fraction and the energy to fracture to the trabecular thickness. The analysis with scanning electron microscopy was troublesome due to the high porosity and surface roughness of the samples, and therefore merely provided a qualitative overview of the microstructure of the fracture surfaces.