Superior facet fractures of the axis vertebra.

Nine cases of superior facet fractures of the axis vertebra are reported. In seven cases, there were associated odontoid fractures. These fractures can occur in a coronal or sagittal direction, shearing off the anterior or lateral plateau of the facet. In addition, the lateral mass of the atlas may sublux into the depressed facet fracture. The fracture complex should be well documented with conventional radiography and tomography. Computerized tomographic scanning has been found to be particularly helpful in diagnosing these fractures and other injuries about the axis or atlas. Patients with undisplaced or well-reduced facet fractures can be managed satisfactorily by conservative means, but surgery (posterior atlantoaxial fusion) should be considered for unreduced fractures in order to prevent long-term instability, nonunion, malunion, and degenerative arthritis.