Subaxial subluxation after atlantoaxial transarticular screw fixation in rheumatoid patients

Abstract

The most common cervical abnormality associated with rheumatoid arthritis (RA) is atlantoaxial subluxation, and atlantoaxial transarticular screw fixation has proved to be one of the most reliable, stable fixation techniques for treating atlantoaxial subluxation. Following C1-C2 fixation, however, subaxial subluxation reportedly can bring about neurological deterioration and require secondary operative interventions. Rheumatoid patients appear to have a higher risk, but there has been no systematic comparison between rheumatoid and non-rheumatoid patients. Contributing radiological factors to the subluxation have also not been evaluated. The objective of this study was to evaluate subaxial subluxation after atlantoaxial transarticular screw fixation in patients with and without RA and to find contributing factors. Forty-three patients who submitted to atlantoaxial transarticular screw fixation without any concomitant operation were followed up for more than 1 year. Subaxial subluxation and related radiological factors were evaluated by functional X-ray measurements. Statistical analyses showed that aggravations of subluxation of 2.5 mm or greater were more likely to occur in RA patients than in non-RA patients over an average of 4.2 years of follow-up, and postoperative subluxation occurred in the anterior direction in the upper cervical spine. X-ray evaluations revealed that such patients had a significantly smaller postoperative C2-C7 angle, and that the postoperative AA angle correlated negatively with this. Furthermore, anterior subluxation aggravation was significantly correlated with the perioperative atlantoaxial and C2-C7 angle changes, and these two changes were strongly correlated to each other. In conclusion, after atlantoaxial transarticular screw fixation, rheumatoid patients have a greater risk of developing subaxial subluxations. The increase of the atlantoaxial angel at the operation can lead to a decrease in the C2-C7 angle, followed by anterior subluxation of the upper cervical spine and possibly neurological deterioration.

Fig. 1

a A 64-year-old RA woman who had severe anterior atlantoaxial subluxation underwent the atlantoaxial transarticular screw fixation. b She developed a substantial anterior subluxation in C4–C5 with severe neurological deterioration 6 years and 5 months after the operation

Fig. 2

a Pre- and post-operative subluxation (slip) in RA. b The level of the increased anterior and posterior slip. * P < 0.05

Fig. 3

a Correlation between the postoperative AA and C2–C7 angles. b Correlation between the AA and C2–C7 angle changes

Fig. 4

a Difference in AA angle changes between patients with anterior subluxation (slip) and those with no slip. b Difference in C2–C7 angle changes between patients with anterior slip and those with no slip

Fig. 5

C2–C7 angle changes at the preoperative, the immediate postoperative (3 months after the operation) and the latest follow-up in patients with anterior subluxation (slip). * P < 0.05; n.s. not statistically significant