Abstract
Recently some reports on pedicle screwing as one fixation technique in the cervical vertebra have been presented. However, pedicle screws in the cervical spine have not been used widely because the cervical pedicle is thin in comparison with the thoracic or lumbar spine and is adjacent to the spinal cord, nerve roots, and vertebral arteries, which make the surgical procedures complex. In the case of the lumber vertebra which has a thick pedicle, even if there is some dispersion in the screw insertion point or direction, the screw can be inserted into the pedicle without much problem. However, in the case of the cervical spine, it is assumed that the insertion point, direction and the diameter of the screw may be limited. The purpose of this study was to evaluate the morphometry of the pedicle including the vertebral body and to establish an appropriate insertion point, direction, diameter, and length of the screw in order to perform safe and rigid pedicle screwing. Ten cervical specimens from C3 to C7 (50 cervical vertebrae, 100 pedicles) were evaluated with manual measurements. Using the original method that determines the anatomical intramedullary axis of the pedicle, mean inclination of axis, mean outer pedicle height, width, mean inner pedicle height, width and mean thickness of the pedicle cortex were measured. The distance from the entry point superior to the inferior margin of the inferior articular process of the same vertebra and medial to the lateral margin of the lateral mass of the same vertebra were measured. The pedicle axis inclination was also measured. The thinnest pedicle cortex was always the lateral cortex in all-level vertebrae. It was considered that the appropriate diameter of the cervical pedicle screw was 3.0-3.5 mm at C3, C4, C5, 3.5-4.5 mm at C6, 4.0-5.0 mm at C7.
