Cervical vertebra C2 (axis)

Function

Its tooth-like dens is the pivot around which the atlas — and therefore the head — rotates. Strong alar and transverse ligaments tether the dens to the skull base, protecting the spinal cord.

Landmarks

• Dens (odontoid process)
• Body
• Transverse processes
• Bifid spinous process
• Pars interarticularis

Articulations (joints)

• Atlas (atlantoaxial joints)
• C3 (zygapophysial and intervertebral disc joints)

Clinical relevance

Hangman's fracture (pars of C2) and odontoid fractures destabilise the craniocervical junction; rheumatoid arthritis can erode the transverse ligament causing atlantoaxial instability.