This system describes three types of occipital condyle fractures: Type 1, comminuted Type 2, extension of a basilar skull fracture and Type 3, avulsion. Currently, the most commonly used classification system is the Anderson and Montesano classification. However, these injuries may be present on plain radiographs, and a general knowledge of their morphology is useful in order to maintain a high level of suspicion for their presence in the setting of blunt trauma. Occipital condyle fractures are most reliably identified with a thin-slice CT scan of the cervical spine. A number of specific injuries, classifications, and measurement techniques are discussed later. The spinous processes and facet joints should be well aligned and symmetrical as any asymmetry would indicate rotation. When performed correctly, radiographs will include the base of the skull to the upper border of T1 on lateral radiographs and the C3-T1 vertebrae on AP radiographs. Radiographic evaluation of the upper cervical spine begins with obtaining an anteroposterior (AP) view, an open-mouth odontoid view, and a lateral view. Flexion-extension plain radiographs can also be obtained providing information that is not obtained via CT and MRI. Not only are plain radiographs inexpensive and reduce radiation exposure to the patient, they are easy to obtain in the emergency department and in the office postoperatively.

While modalities such as CT and MRI scans have largely taken over the role of initial imaging in the setting of high-energy blunt trauma, radiographs remain as a useful adjunct in the evaluation of the upper cervical spine. Plain radiographs were historically the primary tool for the evaluation of cervical trauma. J Am Acad Orthopaed Surg 2014 22(11): Figure 1, page 719.) (From Bransford RJ, Alton TB, Patel AR, Bellabarba C. Three ligaments traverse from the odontoid to the occipital condyles these include the paired alar ligaments that extend from the cranial tip of the odontoid process to the occipital condyles and a central apical ligament that extends from the tip of the odontoid to the basion. Extrinsic ligaments include the ligamentum nuchae, cranial continuation of the anterior longitudinal ligaments, as well as the ligamentum flavum.

The TAL is an essential stabilizer of the AA articulation. The cruciate ligament complex contains the transverse atlantoaxial ligament (TAL), the most structurally important part of the complex, as well as longitudinal fibers that extend from the foramen magnum to the axis. Intrinsic ligaments include the tectorial membrane (rostral continuation of the posterior longitudinal ligament), the cruciate ligament complex, and the alar and apical ligaments ( Fig. Ligaments of the CCJ and atlantoaxial (AA) articulations are separated into two groups: intrinsic and extrinsic ligaments. Due to the significant amount of motion in the upper cervical spine, the ligamentous support of this region is pivotal to maintaining adequate stability. The C1–2 joint is responsible for approximately 40 degrees of axial rotation in each direction, that is, 40% of total axial rotation of the cervical spine. This is more than any other single cervical level.

The CCJ accommodates approximately 45 degrees of flexion extension. A large proportion of overall cervical motion comes from the upper cervical spine between the CCJ and C2. The upper cervical spine contains the craniocervical junction (CCJ), the atlas or C1, and the axis or C2.

X ray spine cervical