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Normal Spine Anatomy


Imaging Anatomy

There are 33 spinal vertebrae, which comprise 2 components: A cylindrical ventral bone mass, which is the vertebral body , and the dorsal arch .

7 cervical, 12 thoracic, 5 lumbar bodies

  • 5 fused elements form the sacrum

  • 4-5 irregular ossicles form the coccyx

Arch

  • 2 pedicles, 2 laminae, 7 processes (1 spinous, 4 articular, 2 transverse)

Pedicles attach to the dorsolateral aspect of the body. Pedicles unite with a pair of arched flat laminae. Lamina capped by dorsal projection are called the spinous process. Transverse processes arise from the sides of the arches.

The 2 articular processes (zygapophyses) are diarthrodial joints. The 1st is a superior process bearing a facet with the surface directed dorsally. The 2nd is an inferior process bearing a facet with the surface directed ventrally.

Pars interarticularis is the part of the arch that lies between the superior and inferior articular facets of all subatlantal movable elements. The pars are positioned to receive biomechanical stresses of translational forces displacing superior facets ventrally, whereas inferior facets remain attached to dorsal arch (spondylolysis). C2 exhibits a unique anterior relation between the superior facet and the posteriorly placed inferior facet. This relationship leads to an elongated C2 pars interarticularis, which is the site of the hangman's fracture.

Cervical

The cervical bodies are small and thin relative to the size of the arch and foramen, with the transverse diameter greater than the AP diameter. The lateral edges of the superior surface of the body are turned upward into the uncinate processes. The transverse foramen perforates the transverse processes. The vertebral artery resides within the transverse foramen, most commonly starting at the C6 level.

C1 has no body and forms a circular bony mass. The superior facets of C1 are large ovals that face upward, and the inferior facets are circular in shape. Large transverse processes are present on C1 with fused anterior and posterior tubercles.

The C2 complex consists of the axis body with dens/odontoid process. The odontoid embryologically arises from the centrum of the first cervical vertebrae.

The C7 vertebral body shows a transitional morphology with a prominent spinous process.

Thoracic

Thoracic bodies are heart-shaped and increase in size from superior to inferior. Facets are present for rib articulation, and the laminae are broad and thick. Spinous processes are long and are directed obliquely caudally. Superior facets are thin and directed posteriorly. The T1 vertebral body shows a complete facet for the capitulum of the first rib and an inferior demifacet for capitulum of second rib.

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