A study of cortical bone microdamage and crack morphology utilising confocal microscopy and sequential labelling

Abstract

The formation and accumulation of microdamage in bone plays an important role in the occurrence of stress and fragility fractures as well as in the initiation of bone remodelling. In this study a novel technique is presented for the investigation of bone microdamage and crack morphology using laser scanning confocal microscopy and sequential labelling with chelating fluorochromes. Compact tension fracture specimens machined from bovine tibial cortical bone, were mechanically tested in a wedge loaded crack-propagating tool. Sequential labelling with xylenol orange and calcein allowed for the crack propagation and microdamage progression to be assessed at each stage using confocal microscopy. Both twodimensional confocal images and three-dimensional z-series reconstructions displayed the formation of a microdamage process zone and wake surrounding the main crack. Further imaging demonstrated the significance of the bone microstructure, such as the vasculature and osteocytes, in the distribution of the microdamage.