Surgical anatomy of the C-2 pedicle

Object. The goal of this anatomical study was to investigate the surgical a nd radiographic anatomy of the C-2 pedicle in relation to transpedicular sc rew placement in occipitocervical stabilization and to establish anatomical guidelines for the placement of C-2 pedicle screws. Methods. The C-2 pedicles in 10 cadaveric spines were evaluated using both computerized tomography (CT) scanning and manual measurements. The specimen s were scanned; the mediolateral and rostrocaudal angulations of each pedic le were measured, with the midline sagittal plane and the inferior endplate of the C-2 facet, respectively, as references, and values were recorded in 1 degrees increments by using a digital goniometer. The height, width, and length of the pedicles were also measured on the CT scans. Based on these measurements in conjunction with direct visualization of the C-2 pedicle th rough the C1-2 interlaminar space pedicle screws were then placed. The dist ances from the screw entry point to the midline, C2-3 joint line, and the m edial aspect of the vertebral artery were also measured. Repeated CT scanni ng was then performed to assess screw placement. The average pedicle height, width, and length measured 9.1 mm, 7.9 mm, and 16.6 mm, respectively, and the medial inclination and rostrocaudal angulati on averaged 35.2 degrees and 38.8 degrees, respectively. The cortex of the pedicle was not violated in any of the 20 cadaveric specimens. Conclusions. Adequate preoperative imaging studies in conjunction with dire ct visualization of the C-2 pedicle make transpedicular fixation safe and e ffective.