Anatomic relation between the cervical pedicle and the adjacent neural structures

Study Design. An evaluation of the anatomic relation between the cervical p edicles and the adjacent neural structures. Objectives. To determine quantitatively the anatomic relation of the cervic al pedicles to the adjacent nerve roots and dural sac. Summary of Background Data. Transpedicular screw fixation in the cervical s pine has been reported, but little quantitative data regarding the anatomic relation between the cervical pedicles and the surrounding neural structur es are known. Methods. Twenty cadavers were used for dissection to observe the relations of the cervical pedicles to the adjacent dural sac and nerve roots. After r emoval of whole posterior bony elements including the spinous processes, la minas, and lateral masses, the isthmus of the pedicles, the dural sac, and the nerve roots of C3-C7 were exposed. Direct measurements included the dis tance from the pedicle to the superior and inferior nerve roots and the dur a. Also, the pedicle height and width were measured at its isthmus. Results. No distance was found between the pedicle and the superior nerve r oot, nor between the pedicle and the dural sac at C3-C7 for all specimens. The mean distances between the pedicle and the inferior nerve roots for all specimens ranged from 1.4 to 1.6 mm. The mean pedicle heights and widths f or all specimens at C3-C7 ranged from 6.0 to 6,5 mm and 4.7 to 5.3 mm, resp ectively. A significant difference between male and female specimens was no ted in the pedicle heights for all levels measured (P = 0.001), and in the pedicle widths for the levels of C4 and C6 (P = 0.05). Conclusions. This study suggests that the incidence of neurologic injuries may be higher in screw penetration of the medial or superior cortex of the pedicle than in screw penetration of the inferior cortex of the pedicle.