Lateral subluxation of the atlas in rheumatoid arthritis: a case report and post-mortem study.

The atlantoaxial joints of a patient with lateral subluxation of the atlas were studied post mortem by dissection. There was severe erosion of the left lateral atlantoaxial joint and an asymmetrical erosion of the cartilages of the median atlantoaxial joint which prevented reduction of the lateral subluxation. The atlantoaxial ligaments were remarkably intact. It is emphasised that osseous factors rather than ligaments confer lateral stability to the atlantoaxial joints and that destruction of these leads to lateral subluxation.