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.