Characterisation of Trabecular Bone Structure

The characterisation of trabecular bone structure has until recently relied on morphometric analysis of histological sections although there is now wide availability of bench top non-destructive X-ray-based imaging with the ability to resolve trabecular elements at resolution on the order of ~10 microns. The advent of non-destructive X-ray-based imaging, such as micro-computed tomography (micro-CT) has enabled measurements from image datasets, representing the three-dimensional structure of trabecular bone. Ex vivo studies into trabecular bone structure in osteoporosis have mainly focused on clinically relevant skeletal sites, such as the proximal femur, the distal radius and vertebral bodies. In vivo, the iliac crest and the sternum have been used to obtain material for the diagnosis of metabolic bone diseases including osteoporosis. Metaphyseal bone structure is determined early in development as secondary trabeculae emerge from the primary spongiosa in the epiphyseal plates during endochondral bone growth. After closure of the epiphyseal growth plates at skeletal maturity, bone remodelling becomes the predominant means by which bone is added or removed from the trabecular compartment. From the time of attainment of peak bone mass, studies show that there is a decrease in trabecular bone volume through to older age in both sexes, although not at all sites and not uniformly for males and females. Gender specific changes in trabecular bone are most evident at and after the menopause in females, which is associated with decreased estrogen and associated with reduced androgen production in males. The consequence of menopausal or age-related bone loss for females and males, respectively, is a marked increase in fracture incidence, although the changes to the trabecular bone architecture are different between sexes.