The vertebral artery is located in the transverse foramina of the lower cervical vertebra. The artery is immediately lateral to the vertebral bodies and the intervertebral disk. The vertebral artery is at risk during surgical procedures involving a cervical discectomy or a cervical corpectomy.

The seat at 34 level shows the typical anatomical configuration of the lower cervical vertebra. The transverse foramina are immediately lateral to the vertebral body. The pedicles are along the posterior corners of the vertebral body. The lateral mass contains a significant amount of surface area for load bearing. The posterior arches have a shingle arrangement with slight overlapping of the lamina in extension.

The principal ligaments of the cervical column from an anterior to posterior direction are the anterior longitudinal ligament, posterior longitudinal ligament, annulus fibrosis, ligamentum flavum, interspinous ligament, and ligamentum nuchae.

The vertebral artery enters the transverse foramina typically at the C6 level. At approximately 15% the vertebral artery enters at C7. At 85%, the C7 transverse foramina do not contain the vertebral artery. The vertebral artery takes a convoluted course between C2, C1, and the occiput.

The cervical spine consists of seven cervical vertebrae. C1 and C2 have unique configurations. C3 to C7 have similar anatomic configurations.

A Brooks wire fusion is a posterior C1-C2 arthrodesis. The bone graft rests on the caudal surface of the C1 arch and the cephalad surface of the posterior arch of C2. The posterior wires are sublaminar to both C1 and C2.

A gallie wire fusion between the C1 and C2 vertebral bodies is a posterior fusion between the posterior arches of C1 and C2. Bone grafts rest on the posterior surface of the C1 arch and the posterior surface of the C2 arch. The wire wraps around C1, sublaminar to C1 and around the spinous process of C2. The wire does not encroach the spinal canal at C2.

The C1-C2 transarticular screws cross the joint between the C1 and C2 lateral masses. In comparison to the pedicle screws in C2, the transarticular screws have less medial angulation in the transverse plane and greater vertical inclination in the sagittal plane.

C2 pedicle screws. The pedicles of the C2 vertebra are directed toward the midline and in the cephalad inclination. Pedicle screws in this area impose a technical risk of injury to the vertebral artery laterally, the brain stem and dura medially, C2 nerve root in a cephalad direction and C3 nerve root in a caudal direction. Inferiorly the carotid artery is at risk for injury.

Rotational subluxation between C1 and C2 can also cause compression of the brain stem and potential injury.