Atlantoaxial Instability in older adults: an underrecognized condition beyond rheumatoid arthritis – a retrospective study

Background Atlantoaxial instability (AAI) is a well-recognized complication of rheumatoid arthritis (RA); however, its occurrence in elderly individuals without inflammatory rheumatic disease remains insufficiently investigated. Age-related degenerative and biomechanical changes may predispose geriatric patients to upper cervical instability independent of RA. This study aimed to evaluate the prevalence of radiographic atlantoaxial subluxation (AAS) in geriatric patients with and without RA and to assess whether radiographic AAS may be underrecognized in older adults without rheumatoid arthritis. Methods In this retrospective cross-sectional study, patients who underwent cervical computed tomography or magnetic resonance imaging between January and September 2024 were evaluated. The study population included 206 patients aged ≥ 65 years with RA, 168 age-matched non-RA individuals, and 183 non-RA individuals younger than 65 years. Radiographic atlantodental interval measurements were obtained using standardized techniques, and AAS was defined as an interval exceeding 3 mm. Multivariable logistic regression analysis was performed with adjustment for sex. Results Atlantoaxial subluxation was detected in 25.7% of geriatric RA patients, 12.5% of geriatric non-RA individuals, and 6.0% of younger non-RA individuals ( p < 0.001). Compared with younger non-RA individuals, geriatric patients with RA had significantly higher odds of radiographic AAS (OR 5.39, 95% CI 2.72–10.69), as did geriatric non-RA individuals (OR 2.27, 95% CI 1.06–4.86). Advanced cervical imaging was infrequently requested because of a prior clinical suspicion of atlantoaxial instability (AAI). Conclusions Radiographic atlantoaxial subluxation (AAS) was observed not only in patients with rheumatoid arthritis but also in older adults without RA undergoing advanced cervical imaging. These findings suggest that radiographic AAS may be more frequently observed among older adults undergoing advanced cervical imaging than is generally appreciated. However, the observed prevalence should not be interpreted as representative of the general geriatric population. Further prospective studies are warranted to determine the clinical significance of radiographic AAS and its implications for patient management.