Reconstruction of Vertebral Body with Delayed Posttraumatic Vertebral Collapse---Biomechanical Evaluation and Redesign

Delayed posttraumatic vertebral collapse (Kümmell’s disease) is a rarely reported, poorly documented, and poorly understood phenomenon. Currently, some treatments can be utilized to reconstruct vertebral body with various severity of vertebral collapse. Verteroplasty, kyphoplasty and body augmenter are included, but their effects and advantages haven’t been evaluated and studied in detailed and objectively. Especially, stress distribution on adjacent vertebrae is limited understood. To elucidate these question comparison among three current treatments for the Kümmell’s disease, this study plans to create one inhomogeneous microstructural finite element model of a collapsed vertebra. It can approach a real simulation about cement-filled cavity devoid of bone in vertebra with vertebroplasty. First of all, a three-dimensional finite element model of the intact vertebra was developed based on one cadaver spine. Various percentages of cancellous bone in other models were excavated to simulate different severity of vertebral collapse. Strain adaptive remodeling theory will be used to study vertebral degeneration. Then, three reconstruction surgeries are simulated by this microstructural vertebral model. Stress distribution and remodeling of effected segment and adjacent segments will be compared to know their influence and insufficiencies. In the second year, mechanical testing will be conducted on porcine vertebral models with 80% cleft. Twenty porcine L2-L4 spines were selected and assigned to no treatment, vertebroplasty, kyphoplasty and body augmenter groups. Strain gage were attached on the tip of the cleft. After static loading, fatigue tests are applied to evaluate their survival endurance, respectively. Clinical follow-ups for patients with reconstruction surgery will be made and verify the prediction of above theoretical simulation. In the last year, redesign of implants or devices based on results of FE simulation, mechanical test and clinical experiences will be introduced to improve the treatment for cases with delayed posttraumatic vertebral collapse. This new design will be manufactured as a prototype for following biomechanical evaluations. Necessary documents will be prepared to apply a patent for its future product. With association between biomechanics and clinical experiences, a suitable diagnosis and better treatment for the Kümmell’s disease hopefully come to a better solution by this study.