The Mechanical Microenvironment of Trabecular Bones Subjected to a Physiological Gait Load

This study aims to reveal the mechanical microenvironment of trabecular bones during gait by characterizing two key mechanical signals [strain and wall shear stress (WSS)], and to clarify their relationships with the bone volume fraction (BV/TV).

Forty trabecular bone cubes with varying BV/TV were cropped from three femoral heads and reconstructed by microcomputed tomography images. Subsequently, a Fourier's series-based gait-loading curve was applied on the reconstructed trabecular bones immersed in a bone marrow domain to perform a fluid-structure interaction analysis. Importantly, the two key mechanical signals (i.e., strain and WSS) and BV/TV were correlated, and also the correlation between the strain and WSS was clarified for the first time.

The strain and WSS in trabecular bones exhibited alternating peak patterns during a gait cycle, and they were strongly correlated to the BV/TV. Moreover, the smaller BV/TV yielded lower strain and WSS. Interestingly, when the BV/TV was small, the strain was weakly correlated to the WSS; otherwise, the strain was strongly correlated to the WSS.

From the perspective of the biomechanics, the correlations between the mechanical environment and BV/TV indicate that the deteriorated bone structure and decreased mechanical stimuli might interplay in the development of osteoporosis. In addition, the revealed mechanical microenvironment provides a loading clue for in vitro mechanobiological experiment to understand the bone adaptive remodeling.