3D micro-computed tomography of trabecular and cortical bone architecture with application to a rat model of immobilisation osteoporosis

Bone mass and microarchitecture are the main determinants of bone strength. Three-dimensional micro-computed tomography has the potential to examine c omplete bones of small laboratory animals with very high resolution in a no n-invasive way. In the presented work, the proximal part of the tibiae of h indlimb unloaded and control rats were measured with 3D MicroCT, and the se condary spongiosa of the scanned region was evaluated using direct evaluati on techniques that do not require model assumptions. For determination of t he complete bone status, the cortex of the tibiae was evaluated and charact erised by its thickness. It is shown that with the proposed anatomically co nforming volume of interest (VOI), up to an eight-fold volume increase can be evaluated compared to cubic or spherical VOIs. A pronounced trabecular b one loss of -50 % is seen after 23 days of tail suspension. With the new ev aluation techniques, it is shown that most of this bone loss is caused by t he thinning of trabeculae, and to a lesser extent by a decrease in their nu mber. What changes most radically is the structure type: the remaining bone is more rod-like than the control group's bone. Cortical bone decreases le ss than trabecular bone, with only -18 % after 23 days.