Atlanto-axial subluxation in rheumatoid arthritis

Inflammatory involvement of the atlantoaxial synovial joints causes erosive changes in the odontoid process (anteriorly at the synovial joint with the C1 arch, and posteriorly at the synovial joint with the transverse ligament) and decalcification and loosening of the insertion of the transverse liga- ment on the atlas. These changes lead to instability allowing a scissoring effect with anterior sublux- ation of C1 on C2. AAS occurs in ≈ 25% of patients with RA ¹⁾

Mean time between onset of RA symptoms to the diagnosis of AAS in 15 patients: 14 years ²⁾.