Effects of μCT and FE resolution in expressing anisotropic properties in vertebral cancellous bone

Abstract

With an aging population lower back pain is a growing concern amongst many people. Recent developments in FE have made possible the simulation of complex geometries, such as trabecular bone. Most current techniques homogenise vertebrae into solids with averaged material properties. This is undesirable as analysis on the effects within trabecular tissue is impossible. As vertebral tissue is highly anisotropic this study investigates the effects on anisotropy when the mesh resolution and orientation are varied. Trabecular cubes were taken from a human donor at different orientations around the medial-lateral axis (0°, 45°, 90°) and tested in all three axes. Prior to testing they were CT scanned (X-Tek), reconstructed (CTPro) for and meshed (ScanlP). The full size scans were linearly downsampled to 32pm, 50pm, 64pm, 128pm and 256pm. Using a power-law based on material properties in the literature (E=15GPa, p=1800 g/cm3 and v=0.3) each mesh was quasi-statically compressed in all three directions. Our finite-element analysis shows good agreement with the experimental results, showing that a pixel resolution of 64pm is good for preserving anisotropy in vertebral bone. This model was further validated against the other models at different orientations also showing a good agreement with the experimental results.