Mechanical properties of vertebral trabeculae with ageing evaluated with micro-CT

Abstract

The aim of this study was to identify the regional variations in the mechanical properties of vertebral can cellous bones at both the apparent and tissue levels, and their relative differences with respect to ageing. Ninety trabecular specimens were obtained from six normal L4 vertebral bodies of six male cadavers in two age groups, three aged 62 years and three aged 69 years, and were scanned using a high-resolution micro-computed Tomography (micro-CT) system. The obtained micro-CT reconstruction models were then converted to micro-finite element models. Micro-finite element analyses were done to determine the apparent Young's moduli and tissue-level von Mises stress distribution for each trabecular specimen in the longitudinal direction (on-axis direction), and medial-lateral and anterior-posterior directions (off-axis directions), respectively. Regional variations about the mechanical properties at both apparent and tissue levels in different transverse layers and vertical columns within and between the two age groups were then analyzed. The results showed significant decreases in the apparent Young's moduli and tissue level von Mises stresses in each direction with ageing; those in the two off-axis directions decreased more with ageing compared with the longitudinal direction, and there were no statistically significant differences between the mechanical properties in the two off-axis directions. The mechanical properties followed their own patterns of regional variations within each group, suggesting both mechanical and age-related adaptation. This study offered an insight into the distributions and variations of mechanical properties within a vertebral body. The mechanical properties calculated from this study may serve as reference for gender and ethnic comparisons and may help us to better understand the regional fracture risk and mechanisms of vertebral fracture, and prevent osteoporotic fracture in older individuals. © 2007 Springer-Verlag Berlin Heidelberg.