Anterior compression fractures of the thoracolumbar spine typically occur after a flexion type of injury, such asa fall onto the buttocks with axial load. Important in understand- ing this type of fracture is attention to the direction of forces applied. Weight is carried by the spine on An axis that runs close to the center of the intervertebral disc. In flexion injuries, this axis becomes the point of a fulcrum. with compression forces acting anterior to this axis and distrac- tion forces, posteriorly(Fig. 6-9). Because the distance from the fulcrum to the posterior spinous ligament is four times the distance from the axis to the anterior longitudinal ligament, the anterior compression force during flexion injury is four times greater than the distraction force that occurs posteriorly. It is for this reason that these flexion forces leave the posterior portion of the spine intact when causing a compression fracture of the anterior vertebral bod