Joints of the Neck

Competency

AN43.1: Describe and demonstrate the movements with muscles producing the movements of atlanto-occipital joint and atlantoaxial joint.

JOINTS OF THE NECK

– The joints of the neck are classified into two groups:

1. Craniovertebral joints

  • Atlanto-occipital joints.
  • Atlanto-axial joints.

2. Typical cervical joints

  • Joints between the lower six cervical vertebrae (C2–C7).

TYPICAL CERVICAL JOINTS

  • The typical cervical joints connect adjacent vertebrae from C2 downwards.
  • They resemble the intervertebral joints found in other regions of the vertebral column.

Classification

1. Joints between vertebral bodies

  • Intervertebral symphyses (secondary cartilaginous joints).
  • Uncovertebral joints (joints of Luschka).

2. Joints between vertebral arches

  • Zygapophyseal joints between adjacent articular processes.
  • Fibrous connections (syndesmoses) between adjacent laminae, spinous processes, and transverse processes.

Joint between Vertebral Bodies

– Adjacent cervical vertebral bodies are connected through two types of articulations:

1. Intervertebral Symphysis

– It is a secondary cartilaginous joint between the central portions of adjacent vertebral bodies.

2. Uncovertebral Joint (Joint of Luschka)

  • It is formed between the uncinate process of a cervical vertebra and the corresponding lateral margin of the vertebral body above.
  • It is commonly described as a plane synovial articulation, although its classification as a true synovial joint remains debated.

Intervertebral Symphysis (Secondary Cartilaginous Joints)

– These joints connect adjacent vertebral bodies, beginning between C2 and C3.

Features

  1. Articular surfaces: The adjoining vertebral endplates are covered by hyaline cartilage.
  2. Intervertebral disc: A fibrocartilaginous disc connects adjacent vertebral bodies and provides stability and shock absorption.

Note: No intervertebral disc is present between the atlas (C1) and axis (C2).

Ligaments

1. Anterior Longitudinal Ligament

  • It is a strong fibrous band extending along the anterior surfaces of the vertebral bodies and intervertebral discs.
  • Superiorly, it continues towards the base of the occipital bone through the anterior atlanto-axial and atlanto-occipital membranes.
  • It strengthens the vertebral column and limits excessive extension.

2. Posterior Longitudinal Ligament

  • It extends along the posterior surfaces of the vertebral bodies and intervertebral discs within the vertebral canal.
  • Above the axis (C2), it continues upwards as the tectorial membrane, which attaches to the basilar part of the occipital bone.

It helps stabilise the vertebral column and limits excessive flexion.

Clinical Anatomy

Cervical Intervertebral Disc Prolapse

  • Cervical disc herniation commonly occurs at the C5–C6 and C6–C7 levels.
  • The herniated disc may compress the adjoining cervical spinal nerve root, producing pain, tingling, numbness, or muscular weakness.
  • C5–C6 disc herniation: It commonly compresses the C6 nerve root, causing pain and sensory disturbances along the lateral forearm, thumb, and index finger.

C6–C7 disc herniation: It commonly compresses the C7 nerve root, producing pain and paraesthesia along the posterior arm, forearm, and middle finger.

Joints of Luschka

  • The joints of Luschka, also called uncovertebral joints, are articulations between the uncinate processes of the lower cervical vertebrae and the lateral margins of the vertebral bodies above.
  • They are usually present from C3 to C7.
  • They are traditionally classified as plane synovial joints, although their status as true synovial joints remains debated.

They help guide cervical movements and contribute to the stability of the vertebral column.

Clinical Anatomy

Cervical Spondylosis

  • Cervical spondylosis refers to age-related degenerative changes affecting the cervical intervertebral discs, vertebral bodies, and facet joints.
  • These changes may produce disc degeneration, osteophyte formation, and narrowing of the intervertebral foramina.
  • Compression of cervical spinal nerve roots may cause radiating pain, numbness, tingling, or weakness in the upper limb.

Osteophytes

  • Uncovertebral joints are common sites of osteophyte formation.
  • These bony projections may narrow the intervertebral foramina and compress cervical nerve roots.

Occasionally, osteophytes may compress the vertebral artery and cause vertebrobasilar insufficiency, particularly during neck movements.

Joints between Vertebral Arches

– These joints include:

  1. Zygapophyseal (facet) joints.
  2. Intervertebral syndesmoses.
Facet joint (zygapophyseal joint)
  • These are plane synovial joints formed between the superior and inferior articular processes of adjacent vertebrae.
  • Their articular surfaces are covered by hyaline cartilage and enclosed within fibrous capsules.
  • They permit gliding movements that contribute to flexion, extension, lateral flexion, and rotation of the neck.
Intervertebral syndesmoses

– These are fibrous connections between adjacent vertebral arches.

1. Syndesmoses Between Laminae

  • Adjacent laminae are connected by the ligamenta flava.
  • Each ligamentum flavum extends between the lamina of the vertebra above and the lamina below.
  • It contains abundant yellow elastic fibres and assists in restoring the vertebral column after flexion.

2. Syndesmoses Between Spinous Processes

  • Adjacent spinous processes are connected by interspinous ligaments.
  • The supraspinous ligament is represented in the cervical region by the ligamentum nuchae.

3. Syndesmoses Between Transverse Processes

– Adjacent transverse processes are connected by relatively weak intertransverse fibrous bands.

Nerve Supply

  • The facet joints are supplied mainly by the medial branches of the posterior rami of adjoining spinal nerves.
  • The intervertebral discs receive sensory fibres from sinuvertebral nerves and neighbouring spinal nerve branches.

Movement of Cervical Vertebral Column (Cervical Spine)

– The cervical spine permits the following movements:

  1. Flexion: Forward bending of the neck.
  2. Extension: Backward bending of the neck.
  3. Lateral flexion: Bending the neck towards either shoulder.
  4. Rotation: Turning the head and neck towards either side.
  5. Circumduction: A combination of flexion, extension, and lateral flexion, producing a circular movement.

CRANIOVERTEBRAL JOINT

Atlantoaxial Joint

  • The atlanto-axial joints are articulations between the atlas (C1) and axis (C2).
  • They consist of three synovial joints:
    1. One median atlanto-axial joint.
    2. Two lateral atlanto-axial joints.
Median atlantoaxial joint

Type

– It is a pivot variety of synovial joint.

Articular Surfaces

– The median atlanto-axial joint is formed by:

  1. Anterior articular facet of the dens (odontoid process) of the axis.
  2. Posterior articular facet of the anterior arch of the atlas.
  3. Posterior articular facet of the dens and the transverse ligament of the atlas.

– The dens articulates anteriorly with the atlas and posteriorly with the transverse ligament through separate synovial cavities.

Ligaments

1. Fibrous Capsule

  • A loose fibrous capsule surrounds the synovial articulation between the dens and anterior arch of the atlas.
  • It permits rotation of the atlas around the dens.

2. Transverse Ligament of Atlas

  • It extends between the medial tubercles of the lateral masses of the atlas.
  • It passes posterior to the dens and holds it against the anterior arch of the atlas.
  • It prevents posterior displacement of the dens relative to the atlas, protecting the spinal cord.

3. Cruciform Ligament

  • It consists of the transverse ligament and its superior and inferior longitudinal bands.
  • Superior longitudinal band: It extends from the transverse ligament to the basilar part of the occipital bone.
  • Inferior longitudinal band: It extends from the transverse ligament to the posterior surface of the body of the axis.
  • These bands form a cruciform arrangement and stabilise the craniovertebral junction.

4. Apical Ligament of Dens

  • It extends from the apex of the dens to the anterior margin of the foramen magnum.
  • It is a slender ligament that provides minor support to the craniovertebral junction.

5. Alar Ligaments

  • These are paired, strong fibrous bands extending from the superolateral aspects of the dens to the medial surfaces of the occipital condyles.
  • They restrict excessive rotation and lateral flexion of the head.
  • They are therefore called check ligaments.

6. Tectorial Membrane

  • It is the superior continuation of the posterior longitudinal ligament.
  • It extends from the posterior surface of the body of the axis to the basilar part of the occipital bone.
  • It lies posterior to the cruciform ligament and provides additional stability to the craniovertebral junction.
Lateral atlantoaxial joint

– These are paired synovial joints situated between the lateral masses of the atlas and the superior articular processes of the axis.

Type

– They are plane synovial joints.

Articular Surfaces

  • Superiorly: Inferior articular facets of the atlas.
  • Inferiorly: Superior articular facets of the axis.
  • The articular surfaces are covered by hyaline cartilage.

Ligaments

  • Fibrous capsules: Each joint is enclosed by a loose capsule attached around the margins of the articular surfaces.
  • Anterior atlanto-axial membrane: It connects the anterior arch of the atlas to the anterior surface of the axis.
  • Posterior atlanto-axial membrane: It connects the posterior arch of the atlas to the laminae of the axis.
  • The cruciform and alar ligaments provide additional stability to the atlanto-axial complex.

Movements

  • All three atlanto-axial joints act together during rotation of the head.
  • The atlas and skull rotate together around the dens of the axis, producing the ‘No’ movement.
  • Approximately half of the total cervical rotation occurs at the atlanto-axial joints.

Excessive rotation is limited mainly by the alar ligaments.

Clinical Anatomy

Odontoid Fracture

  • Fracture of the dens may occur following trauma to the upper cervical spine.
  • Displacement of the fractured fragment may produce atlanto-axial instability and compression of the spinal cord.
  • Severe injuries may damage the upper cervical spinal cord or cervicomedullary junction, resulting in neurological deficits.

Hangman’s Fracture

  • A hangman’s fracture is a bilateral fracture involving the pars interarticularis of the axis (C2).
  • It may cause anterior displacement of C2 over C3, producing traumatic spondylolisthesis.
  • It commonly occurs following high-energy hyperextension injuries, particularly motor vehicle accidents and falls.
  • Severe displacement or associated ligamentous injury may cause cervical instability and neurological damage.

Judicial Hanging

  • Judicial hanging may produce severe hyperextension and distraction injuries of the upper cervical spine.
  • These injuries may involve fractures or dislocations of C2, including a hangman’s fracture.

Fatal neurological injury may occur if the upper cervical spinal cord or cervicomedullary junction is severely damaged.

Important Questions

  • Write a short note on intervertebral disc.
  • Write a short note on atlanto-occipital joints.
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