An accurate analysis and quantification of microdamage is critical to understand how microdamage affects the mechanics and biology of bone fragility. In this study we demonstrate the development and validation of a novel in vitro micro-computed tomography (microCT) method that employs lead–uranyl acetate as a radio-opaque contrast agent for automated quantification of microdamage in trabecular bone. Human trabecular bone cores were extracted from the femoral neck, scanned via microCT, loaded in unconfined compression to a range of apparent strains (0.5% to 2.25%), stained in lead–uranyl acetate, and subsequently re-scanned via microCT. An investigation of the regions containing microdamage using the backscatter mode of a scanning electron microscope (BSEM) showed that the lead–uranyl sulfide complex was an effective contrast agent for microdamage in bone. Damaged volume fraction (DV/BV), as determined by microCT, increased exponentially with respect to applied strains and proportionately to mechanically determined modulus reduction (p < 0.001). Furthermore, the formation of microdamage was observed to occur before any apparent stiffness loss, suggesting that the localized tissue yielding occurs prior to the structural yielding of trabecular bone. This non-invasive in vitro technique for the detection of microdamage using microCT may serve as a valuable complement to existing morphometric analyses of bone.
Keywords:
Trabecular bone; Microdamage; MicroCT; Bone imaging; Bone histomorphometry