THE LOCATION OF THE CERVICAL NERVE ROOTS ON THE POSTERIOR ASPECT OF THE CERVICAL-SPINE

Study Design. This study analyzed anatomic parameters between the midp oint of cervical vertebral lateral the mass as seen on the superficial , posterior aspect of the mass and cervical nerve roots. Posterior cer vical dissection was performed, with the midpoint of the lateral masse s kept intact and the nerve roots exposed. Objective, To quantitativel y determine the location of the cervical nerve roots and the transvers e foramina, indicating vertebral artery placement relative to the post erior aspect of the cervical spine. Summary of Background Data, Poster ior plate-screw fixation of the cervical spine has been widely used to treat unstable fractures of the cervical spine. However, injury to th e spinal nerve roots during the procedure remains an important concern . No previous anatomic study regarding the location of the cervical ne rve roots relative to the posterior aspect of the cervical spine has b een reported. Methods. Fifteen specimens were obtained for study of th e cervical spine. Laminectomy and partial removal of the superior and inferior articular facets then were performed on C2-C3 through C7-T1 t o expose the nerve roots and dura. Photographs, containing a reference scale, were taken simultaneously perpendicular to the sagittal and tr ansverse planes of the specimen. Using enlarged versions of the photog raphs, independent measurements by several observers were taken from t he superficial, posterior center of each lateral mass to the nerve roo t superiorly and inferiorly,and to the lateral limits of the dura. Ver tebrae from an additional 20 spines were examined to determine the pos ition of the transverse foramina relative to the lateral mass of the v ertebrae. Results. The results showed that for C3-C7, the average dist ance from the superficial, posterior center of the lateral mass to the nerve root superiorly was 5.7 +/- 1.5 mm. Inferiorly, the average dis tance was 5.5 +/- 0.8 mm. The average distance from the lateral mass t o the spinal cord dura was 9.2 +/- 1.4 mm, and the average medial angl e of the nerve root was 76.3 degrees + 4.4 degrees. For cervical verte brae C3-C5, the transverse foramina were situated medial to the poster ior center of the lateral mass. At the C6 level, the transverse forami na were situated ,anterior to the posterior midpoint of the lateral ma ss. Conclusion. This study demonstrates that the posterior midpoint of the lateral mass is a safe point for initiating screw insertion.