Spine fractures are the hallmark of osteoporosis, affecting one in three women and one in five men over the age of 50. Yet how these fractures occur and what factors affect the likelihood of fracture remain poorly understood. Our laboratory has developed an experimental method for 3-D, quantitative visualization of the initiation and progression of spine fractures. This method is

based on volumetric digital image correlation (VDIC; or digital volume correlation (DVC)) and is suitable for quantifying the highly non-uniform deformation fields—both throughout the interior of the bone and on bone surface—that occur during failure. By employing this method in our laboratory studies, we have been able to identify microstructural and anatomical features that are associated with initiation and propagation of failure. Interestingly, a characteristic length is observed in the deformations which is dependent on age- and disease-related changes in microstructure and material properties. These results provide a strong biomechanical rationale for one of the clinical methods used to screen for vertebral fracture; however, they also counter pervasive assumptions that regions of low density in the vertebra are the "weak links" and fail first. Through comparison of our experimental measurements to clinically translatable, image-based finite element modeling, this work charts a clear path towards obtaining accurate, patient-specific predictions of fracture risk in the spine