Prediction of Bone Quality of Remodeling Trabeculae Using Multi-Scale Stress Analyses with a Homogenization Technique Reflecting Material Anisotropy

Abstract

High stress in osteoporotic bone that leads to fracture is related to time-dependent changes of bone quality, which is defined by the trabecular structure and the material anisotropy derived from biological apatite (BA) crystallite orientation, with loss of bone mass. To assess and estimate the relativity of variation with time of bone quality, bone mass and fracture risk for the same subject in the future, prediction of remodeling and change in stress distribution in bone is necessary. We established a computational framework with multi-scale stress analyses and remodeling simulations. Then, using healthy and osteoporotic pig’s trabeculae, stress analyses of their remodeled tissue considering BA orientation were performed. The homogenized stiffness in the direction which had adapted to the mechanical environment was high even though bone mass decreased. The relationship between the present percentage of the high stress and the decrease of bone density was not proportional in the osteoporotic remodeling process, but it increased more when the bone mass decreased. These findings suggest that future fracture risk could be detected in more detail by time-dependent variance of bone quality, and the relationship between bone mass, bone quality, and fracture risk could be potentially elucidated by our computational frameworks.