Biomechanics of cervical spine and spinal cord injury under combined axial compression and lateral bending loading

Cervical spine and spinal cord injuries are significant health concerns. Although lateral forces are present during real-world head-first impacts, there is a lack of information about combined lateral bending moments with axial compression. The general aim of this research was to evaluate the effects of lateral bending in dynamic axial compression of the cervical spine on kinetics, kinematics, canal occlusions, and injuries of the cervical spine and this required the development of novel loading and measurement apparatus. We experienced technical challenges in experimentally producing lateral bending moments requiring novel loading methods. Also, as acoustic emission (AE) signals could provide more objective estimates of the timing of injuries produced experimentally, these techniques were developed for use in the spine. In Study 1, techniques were developed to measure the time of injury of isolated spinal components using AE signals. Injuries to human cadaver vertebral bodies resulted in AE signals with higher amplitudes and frequencies than those from ligamentum flavum specimens. Study 2 presented a theoretical and experimental evaluation of the effects of test configuration on bending moments during eccentric axial compression. Design recommendations were provided that allowed us to apply appropriate bending moments in the subsequent studies. In Studies 3, 4, and 5 dynamic axial compression forces with lateral eccentricities were applied to human cadaver cervical spine segments and AE signals were used to detect the time of injury. High lateral eccentricities resulted in lower peak axial forces, inferior displacements, and canal occlusions and greater peak ipsilateral bending moments, bending rotations, displacements, and spinal flexibilities in lateral bending and axial rotation compared to low eccentricity impacts. Also, low and high lateral eccentricities produced primarily hard and soft tissue injuries, respectively. In this three-vertebra model, AE signals from injuries to endplates and/or vertebral bodies had higher amplitudes and frequencies than those from injuries to the intertransverse ligament and/or facet capsule. The effects of lateral bending in dynamic axial compression on injury mechanisms of the cervical spine and the injury detection techniques demonstrated in this thesis may potentially assist in the development and improvement of injury prevention and treatment strategies.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat