Quantitative assessment of the alignment between human trabecular microstructural orientation and mechanical...

Trabecular bone exhibits a highly organized microarchitecture that adapts to its mechanical loading environment, a concept fundamentally described by Wolff's law. However, direct quantitative evidence linking the trabecular microstructural orientation with mechanical anisotropy remains limited. In this study, we quantitatively assessed the alignment between trabecular microstructural orientation and the apparent stiffness tensor using a micro-CT-based finite element (μFE) framework. Fabric tensors and the orientations of individual trabecular plates and rods were derived using the Mean Intercept Length (MIL) method and Individual Trabecula segmentation (ITS) analysis, respectively. The apparent stiffness tensors were obtained through μFE models subjected to three uniaxial compression and three pure shear loading cases. The results demonstrated a strong alignment between the fabric tensor and the apparent stiffness tensor, with an overall alignment index (λ¯) of 0.92 (IQR: 0.09). Trabecular plates exhibited a high degree of alignment with the apparent stiffness tensor (λ¯: 0.88, IQR: 0.15), whereas trabecular rods demonstrated a substantially lower degree of alignment (λ¯: 0.36, IQR: 0.19). Moreover, the alignment between the principal axis of trabecular plates and the apparent stiffness tensor increased with the degree of anisotropy (DA), while the alignment of trabecular rods decreased with increasing DA. These findings provide quantitative evidence supporting Wolff's law, confirming that trabecular bone architecture is structurally optimized to align with habitual mechanical stress pathways, and highlight the dominant role of trabecular plates in governing the mechanical competence of cancellous bone.