Atlantoaxial subluxation is misalignment of the 1st cervical vertebra (atlas) relative to the 2nd cervical vertebra (axis), which occurs most commonly from hyperflexion, hyperextension, or rotary forces.
(See also Evaluation of Neck and Back Pain and Craniocervical Junction Abnormalities.)
Atlantoaxial subluxation can result most commonly from major trauma, but can also occur nontraumatically in patients with conditions that can affect the cervical spine including rheumatoid arthritis, juvenile idiopathic arthritis, ankylosing spondylitis, and Down syndrome. Atlantoaxial subluxation is very rare.
Symptoms of Atlantoaxial Subluxation
Atlantoaxial subluxation is usually asymptomatic but may cause vague neck pain, occipital headache, or occasionally intermittent (and potentially fatal) cervical spinal cord compression.
Diagnosis of Atlantoaxial Subluxation
Radiographs
MRI to assess the integrity of the ligaments
Radiographs of the cervical spine showing atlantoaxial subluxation and subaxial subluxation in a patient with rheumatoid arthritis. The lateral views of the cervical spine were taken in neck extension (on left) and flexion (on right). In flexion, the anterior arch of C1 is far anterior to the dens of C2 (posterior to the black arrow), indicating anterior subluxation. This finding is not evident in extension (black arrow), indicating that atlantoaxial subluxation is dynamic. Anterolisthesis (slipping forward of the upper vertebral body, shown by white arrowheads) is also present at C2-C3 and C3-C4 in extension and at C3-C4 and C4-C5 in flexion.
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Atlantoaxial subluxation is usually diagnosed with flexion and extension cervical radiographs. Views during flexion, as tolerated by the patient, show dynamic instability of the entire cervical spine. Movement below the C1-C2 level is defined by flexion and extension views showing increased angulation of 10 degrees and translation of greater than or equal to 3 mm. If radiographs are abnormal or if they are normal but subluxation is still suspected, MRI, which is more sensitive, should be performed. MRI also provides the most sensitive evaluation of spinal cord compression and is performed immediately if cord compression is suspected.
Treatment of Atlantoaxial Subluxation
Treatment of symptoms
Cervical immobilization
Surgery
Indications for treatment of atlantoaxial subluxation include pain, neurologic deficits, and potential spinal instability. Treatment includes symptomatic measures (eg, analgesics) and cervical immobilization, usually beginning with a rigid cervical collar. Urgency of treatment is generally based on symptoms or presence of cord abnormalities on MRI in susceptible patients. In cases where symptoms increase or in acute traumatic injuries, surgery may be needed to stabilize the spine (1).
Treatment reference
1. Yamada T, Yoshii T, Matsukura Y, et al. Retrospective analysis of surgical outcomes for atlantoaxial subluxation. J Orthop Surg Res. 2019;14(1):75. Published 2019 Mar 7. doi:10.1186/s13018-019-1112-2
Key Points
Atlantoaxial subluxation is misalignment of the 1st and 2nd cervical vertebrae, and is a rare condition.
Causes include major trauma or certain diseases that affect the cervical spine including rheumatoid arthritis, juvenile idiopathic arthritis, ankylosing spondylitis, and Down syndrome.
It is usually asymptomatic but may cause vague neck pain, occipital headache, or occasionally intermittent (and potentially fatal) cervical spinal cord compression.
Diagnose with cervical radiographs in flexion and extension, and obtain MRI if cord compression suspected.
Treat with analgesics and cervical immobilization; surgery is required for patients with spinal cord abnormalities on MRI.
