Microdamage in Human Femoral Trabecular Bone Depends on Loading Mode and Pre-existing Damage

INTRODUCTION Microdamage has been cited as an important component of bone quality [1]. Microdamage could affect fracture risk in bone by providing fracture initiation sites, or by decreasing the mechanical integrity of the trabecular network. However, the effects of microdamage are difficult to detect in large populations, because they are much smaller than those of density and architecture [2]. The majority of fractures occur during falls [3], where the principal stresses are off-axis [4]. Multiaxial and off-axis damage mechanics of trabecular bone have not been extensively studied, and would provide insight into fracture progression. The goal of this study was to investigate the formation of microdamage in human femoral trabecular bone on the apparent loading mode, and initial microdamage levels. Specifically the aims were to: 1) determine how the density and lengths of microcracks depend on the applied loading mode and pre-existing damage and 2) to determine the dependence of modulus loss on microdamage.