The relationship between the degree of displacement of the atlas to axis and the clinical data in atlanto-axial subluxation due to rheumatoid arthritis.

INTRODUCTION: The most common type of anatomical cervical spine involvement is atlanto-axial subluxation (AAS) in rheumatoid arthritis (RA). The purpose of this study was to clarify the relationship between the displacement of the atlas to axis and the clinical data obtained in patients with AAS due to RA.

METHODS: Fifty patients with AAS due to RA that were treated by surgery are herein reviewed. Based on the findings of preoperative lateral cervical radiographs in the neutral position, the patients were classified into two groups as follows: a 10 + group with an atlanto-dental interval (ADI) of ≧ 10 mm, and a 10 - group with an ADI < 10 mm.

RESULTS: Preoperative lateral cervical radiographs demonstrated 15 cases to belong to the 10 + group, while 35 cases belonged to the 10 - group. In the preoperative MR imaging, an intramedullary high signal intensity was observed in seven cases that belonged to the 10 + group and in four cases belonging to the 10 - group. Regarding the neurological severity, the 10 + group included significantly more cases showing severe neurological deficits before surgery; however, there was no significant difference between the two groups regarding the presence of severe deficits even after surgery.

CONCLUSIONS: The severe displacement group included significantly more cases showing an intramedullary high signal intensity in the preoperative MR images. Our results also suggest that a severe displacement before surgery affected the presence of neurological deficits before surgery; however, it did not affect the neurological recovery from such severe neurological deficits.