Anatomical considerations for cervical pedicle screw insertion: the use of multiplanar computerized tomography measurements in 122 consecutive clinical cases

Background context: Successful placement of pedicle screws in the cervical spine requires a sufficient three-dimensional understanding of pedicle morphology to allow accurate identification of the screw axis. Purpose: The goal of the present study was to assess morphologic trends from one level to the next with respect to linear and angular parameters associated with the subaxial cervical pedicles. Study design/setting: We evaluated the pedicle morphology of cervical spine using axial and sagittal computed tomography (CT) imaging. The C3-C7 vertebrae in 122 patients (610 vertebrae) were evaluated (age range, 14-93; mean, 48 years). Methods: Thin cut (2.5 mm thickness) axial CT images were measured. Sagittal reconstructions were obtained using 1.25-mm thickness slices. The following pedicle parameters were assessed: pedicle width (PW, the mediolateral diameter of the pedicle isthmus, perpendicular to the pedicle axis), pedicle height (PH, rostro-caudal dimension of the pedicle determined on the sagittal image), maximal screw length (MSL, distance from the posterior cortex of the lateral mass to the anterior wall of the vertebral body along the pedicle axis), and pedicle transverse angle (PTA, angle between the pedicle axis and the midline vertebral body). Results: The overall mean PW and PH ranged from 4.7 to 6.5 mm and 6.4 to 7.0 mm, respectively. For both these parameters there was a trend toward increasing size proceeding caudally in the cervical spine. The mean PW and PH was greater in males than in females, and this difference was statistically significant at all levels (p