Study Notes: Vertebral Column and Cervical Vertebrae

Vertebral Column

Cervical Vertebrae Overview

  • The first two cervical vertebrae (C1 and C2) are atypical as they are structurally modified to join the skull.

  • The seventh vertebra (C7) is also atypical, modified to join the thoracic spine.

  • Atypical and typical vertebrae are discussed in detail in the subsequent sections.

ATLAS (C1)

  • Definition: The atlas is the first cervical vertebra (C1). It has a ring-like structure without a body and features a short spinous process.

  • Anatomy:

    • Consists of:

    • Anterior arch

    • Posterior arch

    • Two lateral masses

    • Two transverse processes

    • The anterior and posterior arches extend between the lateral masses.

  • Transverse Atlantal Ligament: This ligament divides the ring formed by the arches into anterior and posterior portions.

    • Anatomical Relations:

    • The anterior portion receives the dens (odontoid process) of the axis (C2).

    • The posterior portion transmits the proximal spinal cord.

  • Transverse Processes:

    • Longer than those of other cervical vertebrae.

    • Project laterally and slightly inferiorly from the lateral masses.

  • Articular Processes:

    • Each lateral mass bears:

    • A superior articular process (shaped to articulate with the occipital condyles of the cranium).

    • An inferior articular process.

AXIS (C2)

  • Definition: The axis is the second cervical vertebra (C2).

  • Anatomy:

    • Features a strong conical process on the upper surface of its body, known as the dens or odontoid process.

    • The dens is received into the anterior portion of the atlantal ring acting as a pivot for the atlas.

  • Superior Articular Processes:

    • Located on either side of the dens and adapted to join with the inferior articular processes of the atlas.

    • Position and direction differs from other cervical zygapophyseal joints.

  • Inferior Articular Processes:

    • Aligned with the processes of succeeding cervical vertebrae.

  • Laminae:

    • Broad and thick.

  • Spinous Process:

    • Positioned horizontally.

  • Relations with C1 and Occipital Condyles:

    • Fig. 9.8 illustrates the relationship between C1 and C2 with the occipital condyles.

SEVENTH VERTEBRA (C7)

  • Definition: The seventh cervical vertebra, referred to as the vertebra prominens, has a notable prominence.

  • Anatomy:

    • Long, prominent spinous process that projects almost horizontally to the posterior.

    • This spinous process can be easily palpated at the posterior base of the neck serving as a guide for localizing other vertebrae.

TYPICAL CERVICAL VERTEBRAE (C3-C6)

  • Definition: Typical cervical vertebrae, specifically C3 to C6, share common anatomical features.

  • Body Characteristics:

    • Small, oblong body with slightly elongated anteroinferior borders.

    • This shape results in AP overlapping of the bodies in the articulated column.

  • Transverse Processes:

    • Arise partly from the sides of the body and from the vertebral arch.

    • Short and wide, containing transverse foramina for transmitting the vertebral artery and vein.

    • The upper surfaces have a deep concavity for spinal nerve passage.

  • Foramina Structure:

    • Each cervical vertebra has three foramina:

    • Right and left transverse foramina

    • Vertebral foramen

  • Pedicles:

    • Project laterally and posteriorly from the body;

    • Superior and inferior vertebral notches are nearly equal in depth.

  • Laminae:

    • Narrow and thin.

  • Spinous Processes:

    • Short, directed posteriorly and slightly inferiorly; often bifid (double-pointed) tips.

    • Palpable tips lie at the interspace below their corresponding vertebra.

  • Articular Processes:

    • Located posterior to the transverse processes, at the junction of the pedicles and laminae.

    • Form short, thick columns of bone known as articular pillars with fibrocartilaginous articulating surfaces.

  • Zygapophyseal Joints:

    • The facets of the zygapophyseal joints of cervical vertebrae 2 through 7 lie at right angles to the MSP and are visible in lateral projections.

POSITIONING FOR RADIOGRAPHY OF THE CERVICAL SPINE

  • Intervertebral Foramina: Representation:

    • Directed anteriorly at a 45-degree angle from the MSP of the body.

    • Also directed at a 15-degree inferior angle to the horizontal plane.

  • Radiographic Technique for Foramina:

    • Requires a 15-degree longitudinal angulation of the central ray and a 45-degree medial rotation of the patient (or a 45-degree medial angulation of the central ray).

  • Cervical Zygapophyseal Joints Projection:

    • A lateral projection is essential.

    • Positioning rotations are summarized in Table 9.1.

Summary of Positioning Rotations

  • Intervertebral foramina:

    • 45-degree oblique

    • AP axial oblique (side up)

    • PA axial oblique (side down)

    • Lateral

  • Zygapophyseal joint:

    • Lateral

    • 70-degree oblique

    • AP oblique (side up)