The transverse process, intertransverse space, and vertebral artery in anterior approaches to the lower cervical spine.

Object: The microsurgical anatomy of the C3-6 transverse processes and their relationship to the intertransverse space and vertebral artery (VA) were examined with special attention to the aspect exposed in the anterior surgical approach.
Methods: Ten adult cadaveric spines were examined (magnification levels X 3-40) after perfusion of the arteries and veins with colored silicone. The morphological detail of the transverse process and intertransverse space, the distances between selected surgical landmarks and the VA were measured, and the means and standard deviations were calculated. The osseous changes in the anterior root of the transverse process were classified according to their extent. The transverse processes became smaller, and the anterior intertransverse spaces and the width of the VA exposed in the space increased in size proceeding from caudal to rostral levels, thus exposing the VA to increased risk of injury during procedures at cephalad levels. The distance between the medial border of the longus colli muscle and the VA decreased when proceeding caudally from C2-3 to C4-5 interspaces but began to increase at the level of C5-6. The VA coursed closer to the lateral border of the vertebral body than to the medial border of the anterior tubercle of transverse process. Osseous changes consisting of thinning or defects in the anterior root of the transverse process were observed from C-3 to C-5. The thinning was most prominent in the lower half of the anterior root just above where the VA ascends behind the lower edge of the anterior root. The osseous change may reflect the erosive effect of the VA on the anterior root of the transverse process.
Conclusions: This study provides new information regarding the transverse process and especially the anterior root. An awareness of the thinness and defects in the anterior root of the transverse process and the relationships to the surrounding area will aid in reducing VA injury during anterior approaches to the cervical spine.