Abstract
The purpose of this study was to determine whether natural variations in the bone structure of ostensibly identical rat specimens might affect their fracture behavior and mechanism. This was done by scanning four Wistar rat vertebrae samples with a micro-CT scanner, which takes layered two-dimensional images and layers them together to create a three-dimensional representation at a resolution of 30μm3. From this, a finite element model was created and analysed using simulated standard mechanical tests. The finite element models were used to visualize bone density distribution and see how this related to performance under severe loads. It was found that lower overall bone density correlated to an increase in overall fracture rate, as well as a decrease in load to fracture. Bones with stiff outer cortical bone which was thick and dense performed the best, as strain energy density analysis showed it protected the softer internal cancellous bone from damage. vertebrae with isolated regions of stiff bone performed worst, as the mismatch in stiffness caused fractures. These results are expected, however the study shows that although every possible factor to control rat genetics and growth can be accounted for in an animal experiment, variations in bone structure still resulted in large variations in bone mineral density, and therefore large variations in fracture point, fracture severity and stress distribution.
