Learning Objectives

By the end of this section, the learner should be able to:

Describe the anatomical position and components of the cervical spine
Identify the characteristic features of cervical vertebrae
Differentiate the atlas and axis from typical cervical vertebrae
Explain the joints and ligaments of the cervical spine
Recognize key anatomical relationships
Apply anatomical knowledge to common cervical spine injuries

Overview

The cervical spine forms the most superior portion of the vertebral column, extending from the base of the skull to the thoracic vertebrae. It consists of seven cervical vertebrae (C1–C7) and provides support for the head while allowing a wide range of motion.

Two cervical vertebrae are anatomically distinct:

C1 (Atlas)
C2 (Axis)

This section reviews the anatomy, articulations, ligaments, anatomical relationships, and clinical relevance of the cervical spine.

Characteristic Features of Cervical Vertebrae

Typical cervical vertebrae possess several distinguishing features:

Triangular vertebral foramen, accommodating the spinal cord
Bifid spinous processes, where the spinous process divides distally
Transverse foramina within the transverse processes, transmitting:
- Vertebral artery
- Vertebral vein
- Sympathetic nerve fibers

Atlas and Axis

Atlas (C1)

The atlas articulates superiorly with the occipital condyles of the skull and inferiorly with the axis (C2).

Distinctive features include:

Absence of a vertebral body and spinous process
Presence of two lateral masses connected by:
- An anterior arch
- A posterior arch

Each lateral mass contains:

Superior articular facets for articulation with the occipital condyles
Inferior articular facets for articulation with the axis

The anterior arch bears a facet for articulation with the dens of the axis. This articulation is stabilized by the transverse ligament of the atlas, which attaches to the lateral masses.

The posterior arch contains a groove for:

The vertebral artery
The C1 spinal nerve

Axis (C2)

The axis is characterized by the presence of the dens (odontoid process), which projects superiorly from its vertebral body.

Key features:

The dens articulates with the anterior arch of the atlas, forming the medial atlanto-axial joint
This joint permits rotation of the head (e.g., shaking the head “no”)
The superior articular facets of the axis articulate with the inferior facets of the atlas, forming the lateral atlanto-axial joints

Joints of the Cervical Spine

Joints Present Throughout the Vertebral Column

Two types of joints are found throughout the spine:

Intervertebral joints
- Between vertebral bodies
- Joined by intervertebral discs (fibrocartilage)
- Classified as secondary cartilaginous joints (symphyses)
Zygapophysial (facet) joints
- Between the superior and inferior articular processes
- Synovial plane joints

Joints Unique to the Cervical Spine

Atlanto-Axial Joints (×3)

Lateral atlanto-axial joints (×2)
- Plane synovial joints
- Between the inferior facets of C1 and the superior facets of C2
Medial atlanto-axial joint
- Pivot synovial joint
- Between the dens of C2 and the anterior arch of C1

Atlanto-Occipital Joints (×2)

Between:
- Superior facets of the atlas lateral masses
- Occipital condyles of the skull
Condyloid synovial joints
Permit flexion and extension of the head (nodding)

Ligaments of the Cervical Spine

Ligaments Present Throughout the Vertebral Column

Anterior longitudinal ligament
- Limits hyperextension
Posterior longitudinal ligament
- Limits hyperflexion
Ligamentum flavum
- Connects adjacent laminae
- Highly elastic; assists in maintaining posture
Interspinous ligament
- Connects adjacent spinous processes
- Resists excessive flexion

Ligaments Unique to the Cervical Spine

Nuchal ligament
- Continuation of the supraspinous ligament
- Attaches to spinous processes C1–C7
- Provides muscle attachment for the trapezius and deep cervical muscles
Transverse ligament of the atlas
- Connects the lateral masses of C1
- Secures the dens and stabilizes the atlanto-axial joint

Note: Some texts include the interspinous ligament as part of the nuchal ligament in the cervical region.

Anatomical Relationships

The cervical spine has close associations with important neurovascular structures:

The vertebral artery, vein, and sympathetic nerves pass through the transverse foramina
- Exception: C7, where the vertebral artery does not pass through the foramen
Spinal nerves
- Exit above their corresponding vertebrae
- Exception: C7, which has both C7 and C8 spinal nerves, resulting in eight cervical nerves despite seven vertebrae

Clinical Relevance

Jefferson Fracture (Atlas)

Caused by axial loading on an extended neck (e.g., diving injury)
Lateral masses of C1 are forced apart, fracturing the arches
May involve rupture of the transverse ligament
Spinal cord injury is uncommon at C1 due to a large vertebral foramen

Hyperextension (Whiplash) Injury

Commonly occurs in rear-end motor vehicle collisions
Mild injury: damage to the anterior longitudinal ligament
Severe injury: vertebral fractures or dislocation
Worst-case scenario: subluxation, commonly at C2/C3 or C6/C7, with potential spinal cord injury