Comparative assessment of pedicle morphology of the lumbar spine in various degenerative diseases

Measurement of the morphological dimensions of the pedicles of the lumbar spine was conducted using computed tomography (CT) to clarify the difference in pedicle morphology among different lumbar degenerative diseases. The subjects were 136 patients with lumbar spinal disorders who underwent myelography followed by CT scans. They were divided into four groups, that is a group of 25 patients with degenerative spondylolisthesis (DS group), a group of 54 patients with lumbar canal stenosis (LCS group), a group of 42 patients with lumbar disc herniation (LDH group), and a control group of 15 patients with spinal cord tumor in cervicothoracic region but without lumbar diseases (control group). Measurements of the transverse diameter, axial length, and axial angle of the pedicles were performed on CT slices obtained at the middle of the pedicle. The transverse diameter was the width of the isthmus, the axial length was the distance between the anterior of the vertebral body and the posterior of the vertebral arch on a line perpendicular to the line bisecting the isthmus, and the axial angle was the angle between the line perpendicular to the line bisecting the isthmus and the midline of the vertebral body. While there were no significant differences in the mean transverse diameter or axial length among the four groups, the mean axial angle was significantly smaller in the DS and LCS groups when compared to that in the LDH and control groups. In the DS and LCS groups, the pedicles were more sagitally oriented than in the LDH and control groups. Such difference in the axial angle of the pedicles in different lumbar diseases should be taken into consideration when placing at the insertion of pedicle screws, because precise orientation of screw insertion would scarcely allow penetration of the pedicle wall.