Surgical anatomy of the C-2 pedicle.

Abstract

The goal of this anatomical study was to investigate the surgical and radiographic anatomy of the C-2 pedicle in relation to transpedicular screw placement in occipitocervical stabilization and to establish anatomical guidelines for the placement of C-2 pedicle screws. The C-2 pedicles in 10 cadaveric spines were evaluated using both computerized tomography (CT) scanning and manual measurements. The specimens were scanned; the mediolateral and rostrocaudal angulations of each pedicle 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 through the C 1-2 interlaminar space pedicle screws were then placed. The distances from the screw entry point to the midline, C2-3 joint line, and the medial aspect of the vertebral artery were also measured. Repeated CT scanning 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 angulation averaged 35.2 degrees and 38.8 degrees, respectively. The cortex of the pedicle was not violated in any of the 20 cadaveric specimens. Adequate preoperative imaging studies in conjunction with direct visualization of the C-2 pedicle make transpedicular fixation safe and effective.