Direct Visualization of the Initiation and Progression of Vertebral Fractures

Vertebral fractures are the hallmark of osteoporosis, yet the failure mechanisms involved in these fractures are not well understood. Failure patterns within whole vertebrae are typically estimated from finite element analyses or from images acquired after fracture has occurred. Experimental measurement of deformations sustained by vertebrae during injurious loading would enable direct visualization of vertebral failure mechanisms as well as the possibility of validating the results of numerical simulations of vertebral fracture. Time-lapsed micro-computed tomography (μCT) has been used previously to visualize failure processes in excised specimens of trabecular bone [1,2], and methods of digital volume correlation (DVC) can be applied to these types of image series to obtain quantitative information on the deformations that the bone undergoes [3]. However, application of DVC to whole bones has not been reported and involves additional challenges such as the irregular geometry of the volume and the large size of the sets of image data. The overall goal of this study was to develop a DVC-based method for quantifying deformations throughout entire vertebrae as these vertebrae are loaded to failure.