ANATOMICAL CONSIDERATIONS FOR TRANSPEDICULAR SCREW FIXATION IN THE CERVICAL SPINE

This anatomic study was designed to evaluate the feasibility of cervical pedicle for safe transpedicular screw fixation. It was carried out at the Anatomy Department, Faculty of Medicine, Zagazig University and consisted of two parts. The first part was done on 20 specimens of dry adult cervical spine from C3-C7 (200 pedicles) to measure the pedicle height, pedicle width and angulation of the pedicle with the vertebral body. The second part was conducted on the cervical spines of 5 adult formalin-fixed cadavers to do the following measurements: pedicle height, pedicle width at the isthmus, the distance between the pedicle and the superior nerve root, the distance between the pedicle and the inferior nerve root and the distance between the pedicle and the dural sac. The results of this study showed that there is no distance between the pedicle and dural sac and between the pedicle and superior nerve root. There is a small distance between the pedicle and the inferior nerve root (i.e. 1.4-1.7 mm). The mean height of the cervical pedicle ranged from 6 to 6.9 mm with the smallest height at C3 and the largest at C7. The mean width of the pedicle ranged from 4.9 to 6 mm with the smallest width at C3 and largest at C7. The mean angle of the pedicle with the vertebral body ranged from 40 to 50 degrees with the smallest angle at C3 and the largest at C5. Taking into consideration some anatomic variations between individuals, these data in addition to preoperative assessment of axial CT scan and plain X-ray films may help to minimize neural injuries during pedicle screw fixation in the cervical spine.