The most frequent radiological change seen in the cervical spine in rheumatoid arthritis (RA) is atlantoaxial subluxation (AAS). The special importance of AAS lies in the fact that the change can increase the instability of the spine, which often leads to non-traumatic dislocations that sometimes cause severe neurological disturbance. Neurological manifestations, however, often are absent, even in patients with severe AAS.
Radiological measurements were made to define the relationship between radiological changes and neurological symptoms. The interval between the anterior surface of the dens and posterior aspect of the anterior arch of the atlas in flexion (minimal diameter) and the interval between the posterior surface of the dens and the anterior surface of the posterior arch in extension (maximal diameter) were measured. Then instability index (I. I.) was calculated as max. d.- min. d./max. d.×100 (%).
39 patients with AAS were classified into two groups. Group 1 in which the patients had no neurological symptoms or tingling only in their hands included 30 patients; Group 2 in which the patients had neurological abnormalities such as hyperreflexia, pathological reflex, sensory deficits, muscle weakness and gait disturbance included 9 patients. The I. I. of the cases with neurological symptoms was significantly larger than those of cases without neurological symptoms. Minimal diameter was also reliable in the development of neurological symptoms.