Location of transpedicular screws for fixation of the lower thoracic and lumbar spine. Computed tomography of 45 fracture cases.

Postoperative CT examinations of an unselected group of 45 patients with fractures of the thoracolumbar and lumbar spine including 1 patient with traumatically activated spondylolisthesis were analyzed for the location of the 200 screws, the angles of insertion, and the screw vs pedicle diameters. In all cases transpedicular systems had been used for fixation, i.e., the AO-Fixateur Interne in 28 patients, a combination of Teinturier plates and USI screws in 11 patients, and the VSP system in 7 patients. Using a standardized surgical technique and image intensification in 2 planes throughout, 92 percent of all pedicles were instrumented with acceptable deviations from the anatomic axes. Mismatches between the pedicle and the screw diameters were found in 3 instances, and 2 screws were placed in the transverse processes only. Canal encroachment in 13 patients did not impede neural structures. Slight perforation of the anterior cortex of the vertebral body was recorded in 3 percent of cases, but did not cause any complications.