Trabecular bone is a major load-bearing tissue in the musculoskeletal system and experiences multiaxial loads during habitual and non-habitual activities (e.g., trauma) in vivo. Understanding the multiaxial strength and micromechanics of human bone is of great clinical and scientific importance. A better understanding of the mechanical behavior of trabecular bone can improve diagnostic tools used in fracture risk assessment, enhance implant designs and provide insight into structure-function relations and adaptation mechanisms.

Nonlinear, high-resolution, finite element models were used to investigate tissue-level material properties and micromechanics under uniaxial loading, as well as the multiaxial yield behavior for human trabecular bone from the femoral neck. These computational models, which were rigorously validated by a series of experiments, were used to overcome difficulties that exist in experimental testing at the trabecular tissue and apparent levels (e.g., multiaxial loading). In a novel calibration scheme, specimen-specific experimental data were used to obtain first time measures of trabecular tissue elastic modulus and yield strains, which were then compared to cortical bone—which has a similar ultrastructure. Tissue strength was found to be slightly greater for cortical bone. Under uniaxial loading, it was shown that the experimentally observed uniformity of apparent yield strains is primarily a result of the highly oriented architecture that minimizes bending. Most of the small variation that does occur is from the minor non-uniformity of the tissue yield strains. In the absence of experimental data and a complete multiaxial failure criterion for trabecular bone, high-resolution finite element models were also used to investigate the multiaxial yield behavior for almost 900 load cases. Based on these data, a mathematical yield surface was formulated in strain space. The proposed convex and differentiable yield surface in strain space was nearly isotropic and homogeneous.

The trabecular bone mechanical properties obtained in this research both at the tissue and apparent levels, provide a basis for detailed research into mechanisms of bone failure in a variety of clinical and basic biological applications including fracture risk prediction, drug treatment effectiveness, effects of aging, and bone adaptation.