Neck injuries: II. Atlantoaxial dislocation--a pathologic study of 14 traffic fatalities.

C1-C2 vertebral dislocations have not been commonly recognized at autopsy. Among 66 subjects with neck injuries, drawn from a series of 155 traffic fatalities, were 14 with injuries at the level of the atlantoaxial motion segment, ranging in age from 8 months to 93 years. Thirteen had sprains or lacerations of the atlantoaxial facet joints, and one had a healed C1 fracture. Six of the 14 had odontoid fractures. None had transverse ligament lacerations. Injuries of the alar ligaments and the tectorial membrane were frequent. Only 3 subjects had subaxial cervical injury. All 14 had evidence of impact to the head or neck. Four had fractures of the mandible or facial bones, and 5 had skull fractures. Subdural and subarachnoid hemorrhages were found in 7 and 6, respectively. Brainstem lacerations were not uncommon, but only one had a pontomedullary laceration. Spinomedullary cord injuries occurred in 5. Acute neurogenic shock was the major mechanism of death in 9 of the 14, including 5 with major cardiovascular lacerations. Delayed effects of craniocerebral trauma accounted for the majority of the remainder. The biomechanical mechanisms are discussed.