Fractures of the odontoid: a laboratory and clinical study of mechanisms.

Previous reports and a study of the mechanism of injury in 25 cases of fracture of the odontoid suggest that the fracture usually results from a high velocity force directed to the head, producing flexion, extension, or rotation of the upper cervical spine. In a laboratory biomechanical study using cadaver preparations, fractures of the odontoid were produced in 20 specimens from the upper cervical spine, which were loaded in failure in forward and lateral modes.