Cranial subluxation of the odontoid process in rheumatoid arthritis.

In eighteen patients who had long-standing severe rheumatoid polyarthritis, cranial subluxation of the odontoid process was caused by erosion and collapse of both the occipitocervical and the atlantoaxial facet joints. In five of the patients, the subluxation caused impairment of cranial nerves. One patient was tetraparetic. Six patients had a posterior fusion of the spine; of these, three also had laminectomy of the atlas. Operative treatment seemed to arrest the subluxation, but there was appreciable functional improvement in only four of the six patients. During an average of four years of follow-up, in the twelve conservatively treated patients, the cranial subluxation of the odontoid process progressed, on average, from 8.6 to 10.5 millimeters.