Lateral subluxation of the atlas in rheumatoid arthritis.

Two patients with lateral subluxation of the atlas resulting from rheumatoid disease involving the upper cervical spine have been described. The deformity can be suspected on clinical grounds and in one of our two patients spinal cord damage was a sequel. Erosion of the opposing surfaces of the odontoid and lateral masses of the atlas with detachment of the transverse ligament and deeper fibres of the posterior longitudinal ligament appear to underlie this deformity. Radiological confirmation may require AP views with the head tilted to one or other side.