Sagittal profile and balance are crucial to normal spinal physiology. An unrecognized or untreated spinal injury often results in sagittal plane malalignment. We describe normal spinal biomechanics as it relates to posttraumatic kyphosis as well as the treatment of posttraumatic spinal deformity. The spine is unable to support a physiologic load when two of the three spinal columns are destroyed. The center of gravity, which normally lies anterior to the spine, produces a flexion moment that the injured spine is no longer able to resist. Posterior column failure allows further anterior migration of the axis. This biomechanical disequilibrium often results in posttraumatic kyphosis. Surgical intervention is indicated in the treatment of symptomatic progressive kyphosis when there is progression of the deformity, neurologic loss, or pain. Stabilization may require posterior reconstructive techniques or combined anterior and posterior techniques. The restoration of sagittal planes and instantaneous axis of rotation are always the goals of surgical and nonsurgical treatment.