Atlanto-axial articulation

The atlanto-axial articulation is a complex of three synovial joints, which join the atlas (C1) to the axis (C2).

Articulations
  • paired lateral atlanto-axial joints: classified as planar-type joint between the lateral masses of C1 and C2, though somewhat more complex in shape with concavity of the superior axial facets
  • medial atlanto-axial (atlanto-dental) joint: pivot joint with anterior and posterior articulations of odontoid process/dens of C2 and anterior arch and transverse ligament of C1
  • fibrous capsules of the lateral and medial joints are thin and provide only minimal support, therefore ligamentous attachments provide the majority of support
Attachments
  • anterior longitudinal ligament: thick fibrous band attaches from inferior border of anterior arch of C1 to the anterior axial body
  • posterior atlanto-occipital membrane (continuation of ligamenta flava): attaches from lower border of atlantal arch (and more superiorly to the occipital bone) and upper borders of lamina of C2
  • cruciform/cruciate ligaments: superior, transverse and inferior bands posterior to dens; transverse is strongest portion which stabilises odontoid to the lateral mass of C1 limiting lateral motion of C1 over C2 and limiting subluxation of the joint 1
  • accessory atlanto-axial ligament: from posterior body of C2 to lateral mass of C1
  • there are a number of ligaments which attach the axis to the occipital bone including the tectorial membrane, the paired alar ligaments, median apical ligament and the longitudinal parts of the cruciform ligaments
Function

The atlanto-axial joint allows 10-15o of flexion/extension and 30o of axial rotation.

there are a number of congenital anomalies which can affect the atlas, axis and the joint between the two:

  • aplasias, hypoplasias, and clefts of the atlas arches 
  • split atlas

Abnormalities of the axis tend to affect the odontoid process and include 2:

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Article information

rID: 35480
System: Spine
Section: Anatomy
Synonyms or Alternate Spellings:
  • Atlanto-axial joint

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Cases and figures

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    Figure 1: alar and cruciform ligament anatomy
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