There are two different joints present throughout the vertebral column: The joints of the cervical spine can be divided into two groups – those that are present throughout the vertebral column, and those unique to the cervical spine. The axis also contains superior articular facets, which articulate with the inferior articular facets of the atlas to form the two lateral atlanto-axial joints. This allows for rotation of the head independently of the torso. The dens articulates with the anterior arch of the atlas, in doing so creating the medial atlanto-axial joint. The axis (C2) is easily identifiable due to its dens (odontoid process) which extends superiorly from the anterior portion of the vertebra. The posterior arch has a groove for the vertebral artery and C1 spinal nerve. This is secured by the transverse ligament of the atlas – which attaches to the lateral masses. The anterior arch contains a facet for articulation with the dens of the axis. Instead, the atlas has lateral masses which are connected by an anterior and posterior arch. Each lateral mass contains a superior articular facet (for articulation with occipital condyles), and an inferior articular facet (for articulation with C2). It differs from the other cervical vertebrae in that it has no vertebral body and no spinous process. The atlas is the first cervical vertebra and articulates with the occiput of the head and the axis (C2). The atlas and axis have additional features that mark them apart from the other cervical vertebrae. Fig 2 – Characteristic features of a cervical vertebrae Atlas and Axis

3d x ray upper cervical spine