Bone Abstracts

In sharp contrast to the great interest in morphology of the proximal femur in aged individuals, there is a paucity of studies in children. To date, a comprehensive quantitative analysis of trabecular micro-architecture in various biomechanically relevant subregions of the immature proximal femur has been lacking. The aim of this study was to characterize postnatal development of trabecular bone in various regions of the human proximal femur. The study sample was comprised of 18 femora between the ages of 1 month and 12 years from the Laboratory for Anthropology osteological collection. Trabecular architecture was evaluated using micro-computed tomography (Scanco Medical μCT 40) in the following regions of interest: medial, intermediate and lateral femoral neck regions, intertrochanteric region, and femoral head. The data show that the most dramatic changes occur by the end of the first year of life. Namely, during the first year, there is a decrease in bone volume fraction due to a significant reduction in trabecular number, despite slight thickening of trabeculae. The trabeculae mainly had a rod-like shape with decreasing connectivity and increasing separation. In the youngest samples, trabeculae are parallel and mainly longitudinally oriented (high degree of anisotropy), which changes to a less anisotropic arrangement towards the end of the first year. After the first year, due to increased mechanical loading and muscle activity, the trabecular micro-architectural parameters change in a linear manner. Bone volume fraction increases along with the number and thickness of trabeculae. Trabecular separation and connectivity density remained fairly stable, but the rod-like trabeculae gradually changed to a mechanically advantageous plate-like or even honeycomb shape. The degree of anisotropy continuously increased and changed the straight and parallel trabecular arrangement to a distinct trabecular pattern composed of groups of trajectories as seen in adults. Furthermore, all structural changes showed a region-dependent pattern related to differences in stresses/strains experienced in different regions of the proximal femur.