Bone ultrastructure and trabecular microarchitecture.

<p>(A) Elements of the ultrastructure aligned with the microarchitecture, plotted against the distance to bone surface. At the bone surface (distance to bone surface = 0), the majority of the ultrastructure (~60–75%) was aligned with the trabecular microarchitecture. Towards the trabecular core, at 50 μm from the bone surface, this percentage dropped to about ~50%. A random ultrastructural organization would have resulted in a percentage of ~17% only. Sample 4 (from the 77 y.o. male donor) showed an opposite behavior, where the ultrastructure towards the trabecular core was more prominently oriented along the bone surface than the ultrastructure close to the surface. (B) Plot of the percentage of ultrastructural elements with high degree of orientation (DO) against the distance to bone surface. Highly oriented ultrastructural areas were preferentially found closer to the bone surface and constituted about 30% of the bone tissue close to the trabecular surface. Sample 4 (from the 77 y.o. male donor) showed the opposite behavior, where ultrastructural areas with highest DOs were found preferentially towards the trabecular core. (C) Box plot of high-DO domain dimensions, indicating median (red line), 25th and 75th percentile (box edges) and lower and upper extreme datapoints. Ultrastructural domain dimensions were in the order of tens to hundreds of μm. (D) Plot of DO against grayscale values, indicating local mineralization levels. Areas with higher DO were mostly inversely related to local mineralization levels. (E) Plot of DO against distance to skeleton. DO was mostly positively related to the distance to the skeleton. (F) Plot of DO against local surface curvature. DO was mostly positively related to local surface curvature.