In addition to mass density, tissue composition and architecture are the major determinants of the bone mechanical behavior. However, the role of the architectural anisotropy, fabric tensor, on the elastic and yield behavior of human trabecular calcaneus bone has not been fully investigated.
In this study, the local variability of microarchitecture of human trabecular calcaneus bone is investigated using high resolution microCT scanning. Our results show that the microarchitecture in the analyzed regions of human calcanei is anisotropic, with a preferred alignment along the posterior-anterior direction. Strong correlation was found between most scalar architectural parameters and volumetric bone mineral density (vBMD). However, no statistical correlation was found between vBMD and the fabric components. Therefore, only fabric components explain the data variance that cannot be explained by vBMD. This study demonstrates that a multi-directional, fabric-dependent poroelastic ultrasound approach has the capability of characterizing anisotropic bone properties (bone quality) beyond bone mass, and could help to better understand anisotropic changes in bone architecture using ultrasound.
The relationship between the macro and micro velocity fields in a poroelastic RVE is considered to be a function of the tortuosity: a quantitative measure of the effect of the deviation of the pore fluid streamlines from straight (not tortuous) paths in fluid saturated porous media. The procedure for averaging the pore microvelocity over the RVE of poroelastic media by Coussy and by Biot is reviewed in this study and the significant connection between these two procedures is established. The fabric tensor is introduced in the expression of the tortuosity tensor for anisotropic porous media.
Moreover, the apparent modulus of elasticity, yield strain and stress of trabecular human calcanei along multiple directions are measured using micro-finite element method. The ability of the fabric tensor to describe the elastic and yield behavior of trabecular human calcaneus along multiple directions is investigated. The results show that fabric tensor is highly correlated to the modulus of elasticity and yield stress, but poorly correlated to yield strain.