ABSTRACT
C1 (the atlas) is essentially a ring of bone, with articular facets for the occiput and axis. The body of C1 develops into the odontoid process of C2 (the axis). Ligamentous structures stabilizing the occiput to the spine include the apical and alar ligaments. The joint capsules provide additional stability. The most important stabilizer of the atlantoaxial joint is the transverse ligament passing between the lateral masses of the axis posterior to the dens, preventing anterior displacement of the atlas on the axis.
