Each joint is comprised of two concave articular surfaces on the superior aspect of the lateral mass of atlas which articulate with a convex surface on the occipital condyle. The joint is reinforced by fibrous capsules which support each joint.
- anterior atlanto-occipital membrane: dense, thin, broad fibrous structure which joins the upper border of the anterior arch of the atlas (C1) to the anterior inferior surface of the foramen magnum; it is a continuation of the anterior longitudinal ligament and prevents excessive neck extension
- posterior atlanto-occipital membrane: a broad but thin fibrous membrane which attaches the upper border of the posterior arch of the atlas (C1) to the outer margin of the foramen magnum. It is continuous with the posterior atlantoaxial membrane and ligamentum nuchae and lies immediately posterior to the dura. Posteriorly lie the suboccipital muscles. The atlantic (V3) portion of the vertebral artery runs anteriorly to pierce the membrane and dura and become the dural (V4) portion.
The joint capsule is innervated by the C1 nerve.
- Variable degree of communication between the atlanto-occipital joint and the cavity between the dens (odontoid peg) and transverse ligament
- Third occipital condyle (condylus tertius) which may articulate with the anterior arch of the atlas, or the dens
- Paracondylar process
- Occipital condyle hypoplasia
- Division of the superior articular facet of the atlas
Allows for 25o of flexion/extension and around 5o of axial rotation.
Atlanto-occipital dissociation (AOD) represents the most common cervical spine injury following motor-vehicle accident and is usually highly unstable with significant neurological morbidity.
- 1. Hall GC, Kinsman MJ, Nazar RG et-al. Atlanto-occipital dislocation. World J Orthop. 2015;6 (2): 236-43. doi:10.5312/wjo.v6.i2.236 - Free text at pubmed - Pubmed citation
- 2. Offiah CE, Day E. The craniocervical junction: embryology, anatomy, biomechanics and imaging in blunt trauma. Insights into imaging. 8 (1): 29-47. doi:10.1007/s13244-016-0530-5 - Pubmed
- spinal canal
- cervical spine
- thoracic spine
- lumbar spine
- vertebral body
- neural arch
- transitional vertebrae
- ossification centres
- intervertebral disc
- anterior longitudinal ligament
- posterior longitudinal ligament
- posterior ligamentous complex
- cervical spine ligaments
- iliolumbar ligament
- musculature of the vertebral column
- muscles of the neck
- muscles of the back
- gross anatomy
white matter tracts (white matter)
- anterolateral columns
- lateral columns
- dorsal columns
- grey matter
- nerve root
- spinal meninges and spaces
- functional anatomy
- spinal cord blood supply