The C2-C3 cervical intervertebral disc, the atlantooccipital joint
, and the C3-C4 facet joint also can cause CH (9,10).
After reduction, computed tomography was performed and we confirmed the complete reduction of both the atlantooccipital joint and the atlantoaxial joint (Figure 2).
published the second classification for OCFs in 1997, which was aimed at being an efficient treatment guidance; they broadened the definition of instability to include the integrity not only of the atlantooccipital joint but also of the atlantoaxial joint .
Reducing the atlantooccipital joint and the atlantoaxial joint in a halo device and confirming reduction by CT prior to surgery could obviate the need for intraoperative reduction and enable in situ fusion.
This is partly due to the complex anatomy of the AA joint, a tripartite joint located below the atlantooccipital joint
; it is a synovial joint with an articular capsule surrounded by synovial membrane and cartilage [1-3].
 The superior articular facet of the atlas is accommodated within this fossa during the movements of the atlantooccipital joint
. Occasionally, within this fossa, a foramen may be present, which is called as the condylar canal or the posterior condylar canal.
Ultrasonographic study of the nervous structures of the vertebral canal at the atlantooccipital joint
level in adult dogs.
Following elective tracheotomy, the patient was kept in the supine position with the atlantooccipital joint
High-energy trauma produces hyperextension of the atlantooccipital joint (AOJ) , resulting in severe injury of the osseous and ligamentous complex that stabilizes the skull base to the spine .
Caption: Figure 1: Cervical spine CT scan showing type III left occipital condyle fracture (1), asymmetric left odontoid-lateral mass widening (2), lateral subluxation of bilateral C1 lateral masses (3), and widening of the right atlantooccipital joint (4).
Absolute immobility of an occipitalized atlantooccipital joint
results in compensatory hypermobility between the atlas and axis.
Cervical spine malformations and craniovertebral junction abnormalities which lead to hypermobility of atlantooccipital joints
, give rise to neurological and vascular symptoms.