Normal Anatomy of the Spine: What You Need to Know

Except in special circumstances, the vertebrae assume a relatively constant anatomic theme and consist of a vertebral body and a vertebral (neural) arch. The vertebral body serves as a pillar, supporting the head and trunk. The posterior margin of the bodies, along with the vertebral arches, forms the bony spinal canal, protecting the spinal cord. The neural arch is formed by paired pedicles and paired lamina. Seven processes arise from the vertebral arch: paired superior and inferior articular processes, paired transverse processes, and one spinous process. The intervertebral foramen, formed by two adjacent vertebrae, allows for passage of spinal nerves and vessels (1) (Fig. 10.1). The intervertebral disks consist of the inner nucleus pulposus and the outer annulus fibrosis. The main function of the disks is to distribute load and to allow flexion/extension and lateral bending. A remnant of the notochord, the nucleus pulposus, is usually located more dorsally compared to the center of the vertebral body. The annulus fibrosis attaches to the anterior longitudinal ligament (ALL) and posterior longitudinal ligament (PLL) and is also fused to the epiphyseal ring of the vertebral bodies. MRI of a normal disk demonstrates high signal on T2-weighted imaging related to the water content of the nucleus pulposus and inner annulus fibrosis. The outer annulus fibrosis demonstrates low signal on T1and T2-weighted imaging (2) (Fig. 10.2).