Anatomy of Atlas and Axis Vertebrae

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18 Questions

Which of the following is NOT a function of the transverse ligament of the atlas (C1)?

Provides a cartilaginous surface for the dens

What is the typical orientation of the cervical facet joints in the transverse plane?

35-65 degrees

What is the primary function of the uncovertebral joints in the cervical spine?

All of the above

How does the cervical intervertebral disc (IVD) differ from the lumbar IVD?

The cervical IVD has a distinct developmental origin

What is the typical shape of the axis (C2) vertebral body?

Wider than it is deep

What structure passes through the transverse process of the axis (C2) vertebra?

Vertebral artery, vein, and plexus

What is the primary function of the ligamentum nuchae in the cervical spine?

Maintenance of head position during locomotion

What is the total range of motion for flexion and extension at the atlanto-occipital (OA) joint?

20 degrees

What percentage of cervical rotation occurs at the atlanto-axial (AA) joint?

50%

Which of the following is a key function of the uncovertebral joints in the cervical spine?

Repetitive contact due to loss of intervertebral disc height

What is the primary blood supply to the upper cervical spine?

Vertebral artery

What is the primary function of the short (segmental) ligaments in the cervical spine?

Proprioception of the cervical spine

Which of the following statements about the vertebral artery is true?

It enters the foramen magnum after passing through C1

Which of the following muscles is NOT supplied by the vertebral artery?

Longus colli

Which of the following statements about the levator scapulae muscle is true?

If it is shorter on one side, it may provoke contralateral suboccipital muscle spasms and subsequent headaches

Which of the following muscles play an important role in cervical stabilization, according to the text?

Longus colli and longus capitis

Which of the following statements about referred pain from the cervical region is true?

Pain may be referred to the upper extremities, thoracic spine, scapula, and occasionally, the upper chest

Which of the following statements about the onset of cervical symptoms is true?

An insidious onset of symptoms could suggest postural, degenerative, or myofascial origins, or a disease process such as ankylosing spondylitis, cervical spondylosis, or facet syndrome

Study Notes

Atlas (C1)

  • Dens has 2 facets laterally and 1 medially with an anterior arch, stabilized by the transverse ligament to control anterior displacement and allow nodding
  • Provides a cartilaginous surface, along with the alar ligament, to limit flexion and extension, enabling right rotation to occur with left lateral facet sliding anteriorly and right lateral facet sliding posteriorly

Axis (C2-C7)

  • Vertebrae are 50% wider than they are deep
  • Transverse process contains a foramen for the vertebral artery, vein, and plexus, and a groove for the spinal nerve
  • Facet orientation is approximately 45 degrees in the transverse plane with loose capsules, allowing for motion in all planes and more rotation and lateral flexion than other regions

Clinical Pearls

  • The cervical IVD develops distinctly differently from the lumbar disk
  • The orientation of the zygapophyseal joint planes can be thought of as passing through a patient's nose
  • Uncovertebral joints guide cervical flexion and extension, reduce side bending of the cervical spine, prevent posterior translation of neighboring vertebrae, and reinforce the posterolateral aspect of the IVD
  • Degeneration or degradation of the IVD can lead to repeated contact between the bony surfaces of the uncovertebral joint, resulting in hypertrophic changes in the bone

Ligaments

  • Long (continuous): posterior longitudinal ligament and anterior longitudinal ligament
  • Short (segmental): interspinous, intertransversarius, ligamentum flavum, and interlaminar
  • Important for maintaining head position during locomotion and stability of the vertebral column

Atlanto-Occipital Joint

  • Total range of flexion and extension is 20 degrees
  • Important for maintenance of stability of the vertebral column

Atlanto-Axial Joint

  • 50% of cervical rotation occurs at this level
  • A loose fibrous capsule encloses the joints at the articular margins

Blood Supply

  • Vertebral artery arises from the subclavian artery and ascends via transverse foramina of C6-C1
  • Supplies the ipsilateral upper cervical spinal cord

Muscles

  • Lateral and posterior cervical spine muscles: upper trapezius, SCM, scalenes, splenius capitis and cervicis
  • Anterior cervical spine muscles: semispinalis capitis, deep muscles
  • Clinical pearls:
    • Levator scapulae imbalance can cause contralateral suboccipital muscle spasms and headaches
    • Longus colli and longus capitis play an important role in cervical stabilization
    • Referred symptoms from cervical spine can occur in the upper extremities, thoracic spine, scapula, and occasionally the upper chest

Test your knowledge on the anatomy of the Atlas (C1) and Axis (C2) vertebrae, including the dens, transverse ligament, facets, and their role in neck rotation and stability.

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