Biomechanical study of posterior fixation for thoracolumbar burst fractures

In order to provide theoretical support and clinical basis for the choice of surgical methods for patients with thoracolumbar burst fractures, five finite element models of the T10 - L2 segment were established in this work including intact model, burst fracture model, mono-segment pedicle screw fixation, intermediate bilateral pedicle screw fixation, and traditional short-segment pedicle screw fixation. To analyze the biomechanics of the three fixation models, flexion, extension, lateral bending, and rotation moments of 7. 5N-m with a compressive preload of 400 N were imposed on the superior surfaces of the T10 vertebral body. Results showed that the range of motion at the three fixation models decreased for all loading cases, compared with that at the intact model. Compared with the intermediate bilateral pedicle screw fixation model, the largest maximal stress of the pedicle screw at mono-segment pedicle screw fixation model increased by78. 1% in flexion, 87. 8% in extension, 90. 5% in left bend, 81. 3% in right bend, 51. 3% in left rotation,72. 3% in right rotation. In conclusion, the range of motion of the mono-segment pedicle screw fixation model was the most similar to that of the intact model, and it was most likely to protect the original mechanical properties of the spine while restoring the stability of the spine, but the largest maximal stress of pedicle screws was much higher than the intermediate bilateral pedicle screw fixation. For severe damage to the instability, the intermediate bilateral pedicle screw fixation significantly reduced the pedicle screw stress while improving the stability of the spine.