Prevalence and associated factors of anterior atlantoaxial luxation in a nation-wide sample of rheumatoid arthritis patients

Objective To estimate the prevalence of anterior atlantoaxial subluxation (AAS) in patients with rheumatoid arthritis (RA), and to analyse its association with disease markers. Methods Cross-sectional analysis of a cohort of RA patients randomly selected from the clinical registries of 34 centres. AAS, defined as an atlantoaxial displacement in cervical spine X-rays greater than 3 nun on flexion films, was actively searched,for Bivariate and multivariate analysis was performed to examine its association with clinical, functional, and treatment variables. Results AAS was found in 88 out of 736 patients with available cervical radiographs, (prevalence and 95% confidence interval [CI]: 12% [9.7-14.2]). The presence of AAS was highly associated with a Larsen score (0-150) over 50 (OR and 95% CI: 5.31 [2.68-10.55]) RA duration of more than 10 years (4.48 [2.70-7.44]), disease onset before age 50 (4.15 [2.42-7.12]), eye involvement (3.93 [1.63-9.46]), and previous RA related surgery (3.90 [2.46-6.19]). No association was found with rheumatoid factor Multivariate analysis showed that a disease onset before the age of 50, the number of previous DMARD, and, above all, a Larsen score greater than 50 were important independent factors associated with AAS. There is a 33% increased risk,for AAS every 10 units up in the Larsen score. Conclusion AAS is frequent in RA patients, particularly in those with markers of erosive disease.