Normal Anatomy Overview

7 cervical, 12 thoracic, 5 lumbar bodies

• 5 fused elements form sacrum

• 4-5 irregular ossicles form coccyx

Arch

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

• Pedicles attach to dorsolateral aspect of body

• Pedicles unite with pair of arched flat laminae

• Lamina capped by dorsal projection called spinous process

• Transverse processes arise from sides of arches

• 2 articular processes (zygapophyses) are diarthrodial joints: Superior process bearing facet with surface directed dorsally and inferior process bearing facet with surface directed ventrally

Pars interarticulars 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, while 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 fracture.

Cervical

• Cervical bodies are small and thin relative to size of arch and foramen with transverse > AP diameter; lateral edges of superior surface of body are turned upward into uncinate processes; transverse foramen perforates transverse processes

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

• C2 complex consists of axis body with dens/odontoid process; odontoid embryologically arises from centrum of 1st cervical vertebrae

• C7 shows transitional morphology with prominent spinous process

Thoracic

• Bodies are heart-shaped and increase in size from superior to inferior

• Facets are present for rib articulation, and laminae are broad and thick; spinous processes are long, directed obliquely caudally; superior facets are thin and directed posteriorly

• T1 shows complete facet for capitulum of 1st rib and inferior demifacet for capitulum of 2nd rib

• T12 resembles upper lumbar bodies with inferior facet directed more laterally