Experimental biomechanics of vertebral fractures

Vertebral fractures are a severe cause of morbidity and disability. In particular, burst fractures are a common traumatic injury presenting neurological impairment in 47 % of cases. However, diagnosis and planning of the treatment is challenging as the injury originates in highly dynamic conditions. Short-segment pedicle instrumentation (SSPI) in combination with kyphoplasty (SSPI–KP) has been used to provide additional stabilisation of the fracture. However, there is a lack of understanding about the effectiveness SSPI–KP. The aim of this study was to follow the fracture pathway, from onset to the outcome of surgical treatment. The first part focused on the phenomena underlying fracture creation and the dynamics of interpedicular widening (IPW). Although associated with neurological deficit, no previous study has shown how IPW evolves at fracture initiation. Subsequently the performance of treatment was assessed to evaluate how KP can improve SSPI to a simulated early follow-up. Burst fractures were induced in 12 human three-adjacent-vertebrae segments. Following fracture investigation, SSPI and SSPI–KP were performed, and samples underwent fatigue loading. Image processing of high-resolution CT scans was performed to assess anatomical changes at consecutive experimental stages on the treated and adjacent vertebrae. Experiments proved that IPW reaches a maximum at fracture onset and then decreases to the value measured clinically. SSPI–KP marginally improved stability of the treated spine, whilst providing a significant restoration of the endplate geometry. Vertebral body underwent significant changes in height and endplate curvature throughout the fracture pathway. This study provided further insight on the biomechanics of vertebral fractures and the findings can be used to improve and/or develop novel treatments as well as validate numerical models for retrospective assessment of the injury. In addition, outcomes from the collaboration work on the development of a computational simulation may help better understand cancer related vertebral fractures.