Morphological and Mechanical Properties of Bone Structural Units: A Two-Case Study

Abstract

Motivated by an improved understanding of skeletal fragility, the objective of this study was to investigate the relationships between morphological and mechanical properties of bone structural units (BSU). The average orientation of collagen fibers was classified using polarized light microscopy (PLM) and the mean degree of mineralization (MDMB) was quantified by microradiography for a collection of BSU from two donors. The mechanical properties of the same BSU were then measured by nanoindentation and scanning acoustic microscopy (SAM). Surprisingly, the indentation modulus and hardness quantified by nanoindentation were only weakly correlated to MDMB. The longitudinal wave modulus measured by SAM was better related to MDMB but did not correlate with the indentation modulus. There is increasing evidence that the collagenous phase and its bonding to the mineral phase play a significant role in the mechanical properties of bone tissue and deserve more attention in our understanding of bone fragility.