Subaxial antero-posterior dislocation of the cervical spine in rheumatoid arthritis.

A subaxial (below C2) antero-posterior dislocation of the cervical spine was present in 18% of 407 patients with rheumatoid arthritis. The dislocation was as common at only one level as at two more levels and was more severe if the height of the spinous process was reduced. Most of these same patients also had an atlanto-axial dislocation. At follow-up examinations, the frequency of a subaxial dislocation was the same in patients with a severe atlanto-axial dislocation who were receiving conservative treatment as in patients with a cervico-occipital fusion. Neurological symptoms occurred more frequently in patients with an encroached spinal canal and in patients with a reduced height of the entire cervical spine.