An overview on the anatomy of the spine

Cervical spine

The cervical spine is composed of seven vertebrae, with the first two vertebrae known as the atlas (C1) and axis (C2). The atlas contains a thick anterior arch and a thin posterior arch, which is ring-shaped and supports the cranium. The transverse process contains a transverse foramen, through which the artery passes. The vertebral foramen is large in diameter and contains the spinal cord which passes through. There are two arches: posterior and anterior. The anterior arch extends into the two lateral masses that articulate with the occipital condyles and inferior joint facets ( Fig. 1.1 ). The posterior arch is comparatively thinner than the anterior arch and composes the posterior section of the lateral masses.

The body of the axis, C2, is fused to the body of the atlas to form the odontoid process, alternatively called the dens. Similar to the atlas, the transverse process of the axis contains two transverse foramen to allow for passage of the vertebral arteries (see Fig. 1.1 ). Unlike the atlas, the axis has a distinct bifid spinous process, which is formed from two laminae. The atlas and axis articulate between the superior facets of the axis with the inferior articular facet of the atlas, and the inferior articular facets of the axis articulate with the superior articular facets of the third cervical vertebra. Compared with the atlas, the axis has a prominent superior process, does not contain tubercles on the transverse processes, and has a prominent spinous process.

The third to sixth cervical vertebrae (C3–C6) are anatomically similar to each other and different from the atlas and axis. The vertebral bodies are relatively small, and taller on the posterior aspect compared with the anterior part of the body ( Fig. 1.2 ). The joints are formed through the articulation of two uncinate processes upward with the lower parts of the upper vertebrae to compose the uncovertebral joints, alternatively known as the Luschka joints. The distance between the uncinate processes increases gradually descending from C3. The spinous processes at these levels are short and bifid, and protrude posteriorly and inferiorly (see Fig. 1.2 ). The vertebral artery runs transversely through the cervical vertebrae, lateral to the vertebral bodies and medial to the tubercles.

The body of the seventh cervical vertebra, C7, is unique in its appearance as the lateral mass is more elongated in the superior–inferior direction and thinner in the anteroposterior direction. The spinous process of C7 is large and is not bifid, like the levels above.

The cervical spine has two longitudinal ligaments: anterior and posterior. The anterior longitudinal ligament is attached to the vertebral bodies, whereas the posterior longitudinal ligament is attached to the intervertebral disc ( Fig. 1.3 ). The ligaments are utilized as stabilizers for the joints in the cervical spine.