Multivariate Analysis of Risk Factors for Atlantoaxial Osteoarthritis: A Retrospective Cohort Study on Ligament Ossification, Joint Degeneration, and Muscle Fatty Infiltration.

Objective: Atlantoaxial osteoarthritis (AAOA) cause occipitocervical and retroauricular pain and cervical rotation disorder. Few studies have focused on the relationship between cervical spine structure and the prevalence of AAOA in China. This study aimed to investigate whether the inter-atlanto-occipital ligament ossification, uncovertebral joint degeneration and fat infiltration (FI) in the obliquus capitis inferior (OCI) muscles are associated with atlantoaxial arthritis, and to explore other potential risk factors in a clinical cohort from Eastern China.

Methods: We analyzed CT images of the upper cervical spine from 1021 adult trauma patients scanned at our hospital between January 1, 2014, and July 1, 2024. Atlantoaxial osteoarthritis and uncovertebral joint degeneration were categorized as none-to-mild (no osteoarthritis) or moderate-to-severe (osteoarthritis present). Ossification of the inter-atlanto-occipital ligament was graded 0-3 based on its extent. Risk factors for atlantoaxial osteoarthritis were identified using univariate and multivariable logistic regression analyses. Among these patients, 381 underwent cervical MRI, and we assessed fat infiltration (FI) in the inferior oblique muscles, classifying it into quartiles: mild (8.51%-18.49%), moderate (18.67%-31.56%), and severe (31.88%-46.22%). Multivariate regression analysis was then performed to explore the relationship between FI severity and the incidence of AAOA.

Results: The study group consisted of 59.4% men, with a mean age of 50.18 ± 17.23 years, and an AAOA prevalence of 11.6%. In the primary multivariable logistic regression analysis, the following factors were independently associated with AAOA: age ≥ 50 years (OR 30.48, p < 0.001), inter-atlanto-occipital ligament ossification (OR 1.59, p = 0.033), female sex (OR 2.54, p < 0.001), and uncovertebral joint degeneration in the lower cervical spine (OR 2.38, p < 0.001). In a separate multivariate logistic regression analysis that specifically included the degree of fatty infiltration in the inferior oblique muscles, it was found that greater fatty infiltration was also significantly associated with an increased risk of AAOA (OR 3.52, p < 0.001).

Conclusions: Age over 50 years, inter-atlanto-occipital ligament ossification, female sex, and uncovertebral joint degeneration are significant factors associated with atlantoaxial osteoarthritis. Severe fatty infiltration of the inferior oblique muscles may also be a potential risk factor. Delayed diagnosis and treatment may be prevented by prioritizing these risk factors.