Biomechanics of thoracolumbar junction vertebral fractures from various kinematic conditions

Thoracolumbar spine fracture classifications are mainly based on a post-traumatic observation of fracture patterns, which is not sufficient to provide a full understanding of spinal fracture mechanisms. This study aimed to biomechanically analyze known fracture patterns and to study how they relate to fracture mechanisms. The instigation of each fracture type was computationally simulated to assess the fracture process. A refined finite element model of three vertebrae and intervertebral connective tissues was subjected to 51 different dynamic loading conditions divided into four categories: compression, shear, distraction and torsion. Fracture initiation and propagation were analyzed, and time and energy at fracture initiation were computed. To each fracture pattern described in the clinical literature were associated one or several of the simulated fracture patterns and corresponding loading conditions. When compared to each other, torsion resulted in low-energy fractures, compression and shear resulted in medium energy fractures, and distraction resulted in high-energy fractures. Increased velocity resulted in higher-energy fracture for similar loadings. The use of a finite element model provided quantitative characterization of fracture patterns occurrence complementary to clinical and experimental studies, allowing to fully understand spinal fracture biomechanics.