Prevalence of anterior atlantoaxial subluxation and association with established rheumatoid arthritis

Objective: Spinal involvement in rheumatoid arthritis (RA) is limited to the upper cervical spine, leading to cervical spine instability. This study aimed to evaluate the prevalence of anterior atlantoaxial subluxation (aAAS) and its associated risk factors in patients with RA.

Method: This single-centre cross-sectional study 240 patients consecutively were recruited. Radiographs of the cervical spine were obtained in the flexion and neutral neck positions and read by two blinded observers. The diagnosis of aAAS was based on the distance between the anterior aspect of the dens and the posterior aspect of the anterior arch of the atlas, which was >3 mm during flexion. Statistical analysis was performed to determine the predictive factors of aAAS.

Results: Two hundred and forty patients with a mean ± SD age of 56.4 ± 11.4 years were recruited, and 191 (78%) were female. The mean ± SD duration of the disease was 10.2 ± 8.5 years. Of all 25 cases (10.4%) diagnosed with aAAS, the mean anterior atlantodental interval in patients with AAS was 4.19 ± 1.20 mm. One in three patients with aAAS had no neck pain. Patients with aAAS had longer disease duration, lower age at diagnosis, lower body mass index, higher anti-cyclic citrullinated peptide autoantibodies (anti-CCP), more frequent erosion, joint restriction, and joint prostheses. In the multivariate regression model, joint limitation, history of joint prostheses, low BMI, and higher anti-CCP levels were independent predictors of the aAAS.

Conclusion: Thirty-three percent of patients with cervical involvement do not experience neck pain. Cervical involvement should be considered even without neck pain, particularly in established diseases.