C2 vertebra

Last reviewed 01/2018

The axis or second cervical vertebrae is the strongest of the cervical group. It shows similarity to typical cervical vertebrae with some obvious exceptions:

  • odontoid peg or dens:
    • sited anteriorly in the midline
    • results from fusion with body of atlas
    • facet on its anterosuperior surface projects superiorly onto facet of anterior arch of atlas
    • pointed at apex where apical ligament attaches
    • bevelled sides are origins of alar ligaments
    • posteriorly flat surface lying anterior to transverse ligament
  • vertebral canal: oval and broader in coronal plane
  • body: connects to odontoid process medially and superiorly; superior articular processes and transverse processes laterally; and pedicles posterolaterally
  • pedicles: relatively short and sited at junction of lamina, transverse process and body
  • superior articular facet: the key weight-transmitting structure articulating with inferior facets of atlas
    • slightly convex and face superolaterally
    • permit rotation of atlas on axis
  • inferior articular facet:
    • at junction of pedicles and laminae
    • slightly concave
    • surface slopes anteriorly and inferiorly
  • transverse processes:
    • relatively small
    • contain foramen transversarium
    • no anterior tubercle
    • bounded by costotransverse lamella
  • laminae: broad and project posteriorly to spinous process in median plane
  • spinous process:
    • bifid
    • relatively large allowing use as a palpation landmark