Biomechanical effects of short construct spine posterior fixation, in thoracolumbar region with L1 burst fracture

Abstract

One of the most common spinal fractures is thoracolumbar spine fracture and in this area burst fracture contributed approximately 10%–20% of such spinal problems [1–5]. The purpose of this study is to investigate biomechanical effects of anterior decompression and posterior instrumentation and evaluate the role of short-segment pedicle screw instrument in order to preservation of adequate spine stability as well as appropriate spinal segment motion. Finite element model of the spinal segments T11 to L3 was developed to simulate burst fracture of L1 and analyse stabilization method using spinal fusion by cage and bone graft, pedicle screws and short rods for thoracolumbar spine. Computed tomography image datasets were obtained from a local hospital and three dimensional model of the region of interest were developed through manual segmentation. Rods and screws for the construct were modeled in three dimensions with appropriate simplifications to ensure that the simulations could be analysed completely. The vertebrae were assigned with bone material properties and the intervertebral discs were modeled as two parts - the nucleus pulposus and the annular fibrosis. Flexion, extension and lateral bending movements of the spine segment were simulated and the stresses and deformation generated within the vertebral segment as well as within the rods and screws were analysed. Results showed that adequate stabilization can be achieved through fixation at T12 and L2 for burst fracture of L1 and risk of failure at the critical area.