Lateral C1-C2 dislocation complicating a type II odontoid fracture.

We describe a unique C1-C2 lateral dislocation complicating a displaced type II odontoid fracture. We report a 63-year-old female pedestrian involved in a motor vehicle accident who required posterior open reduction and segmental C1-C2 instrumentation and fusion. Radiological examination of the cervical spine demonstrated a lateral dislocation of the atlantoaxial joint with a displaced type II fracture of the odontoid, fracture of the right lateral mass of C1 and left superior articular facet of C2. Neurological examination revealed the patient to be myelopathic and closed halo traction failed to achieve reduction. Due to the irreducible nature of the dislocation, posterior open reduction and segmental C1-C2 instrumentation and fusion was performed. The dislocated C1-C2 articulation was successfully reduced surgically with subsequent bony fusion and resolution of all neurological symptoms and signs at final follow-up. To our knowledge, this the first report of this type of injury. We also review the related literature on this unique injury pattern.