A biomechanical study of thoracolumbar spinal fractures with bone in the canal. Part II. The effect of flexion angulation, distraction, and shortening of the motion segment.

In the second part of this biomechanical study of thoracolumbar spinal fractures with bone in the neural canal contract force on the spinal cord--meningeal complex was measured with relation to varying fracture wedge depth, flexion angulations, and distraction and shortening of the fracture model motion segment. The removal of progressively deeper vertebral body wedges did not change the measured contact force/depth of penetration characteristics, however, the resistance to flexion angulation was decreased. Distraction of the motion segment an average of 5.2 mm increased significantly the contact force at the same depth of penetration compared with the case of normal vertebral body height. Shortening an average of 3.2 mm did not have a significant effect. Flexion angulation to 20 degrees did not change the depth/force characteristic in either the shortened or distracted case.