An evaluation of lateral atlanto-axial displacement in injuries of the cervical spine.

Abstract

Anteroposterior roentgenograms of the cervical spine obtained following trauma frequently show displacement of the lateral articular masses of the atlas with respect to those of the axis. There has been a tendency to discount this finding on the grounds that it can be produced by normal movement of the head and that it is often seen in the absence of injury. We have not encountered in the literature any study correlating the various types of lateral displacement and the frequency of their occurrence in injuries of the cervical spine. This investigation was undertaken because it was our impression that these displacements are more significant than has been suspected. Three separate types of motion are possible in the normal atlanto-axial joint: (a) With flexion of the neck, a slight degree of separation can be demonstrated between the dens and anterior arch of the atlas (3). This motion is not pertinent to our discussion and will not be considered further. (b) Rotation of the atlas about the dens is the ma...