Realignment and surgical fixation of atlanto-axial and subaxial dislocations in rheumatoid arthritis (RA) patients.

One hundred consecutive patients with atlanto-axial dislocation(s) were subjected to posterior occipito-cervical fusion and followed up to 16 1/2 years postoperatively (mean: 4 1/2 years). The mean age at surgery was 60.3 years. At the time of follow-up, 45 patients had died, mostly due to cardiopulmonary disease. Out of the 100 patients, 67% showed a major improvement and in an additional 14% there was a slight or moderate improvement. Some patients with a stable fusion later developed subaxial dislocation(s) necessitating an anterior fusion which in patients with RA is difficult due to poor bone quality. MRI revealed pannus formation around the odontoid peg in many patients, in several to such a degree that cord compression was evident. Following the posterior fixation, the pannus disappeared or was reduced which may at least partly explain the generally favourable operative outcome following the fixation procedure. Early occipito-cervical fusion appears to prevent further vertical dislocation or upwards migration of the odontoid which is a more severe condition, and does not appear to result in increased incidence of subsequent subaxial dislocation(s). Such luxation(s) pose a technically difficult problem since the quality of the patients' own bone usually does not permit a common anterior fusion procedure with autologous graft. In such cases with cord compression, acrylic cement may be used to obtain a normalized realignment.