with compression forces acting anterior to this axis and distraction 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