Atlantoaxial Subluxation in Patients With Psoriatic Arthritis

We aimed to investigate the prevalence and incidence of atlantoaxial subluxation (AAS) in psoriatic arthritis (PsA), identify associated risk factors, and describe the clinical and radiographic characteristics of affected patients.

We included individuals from our observational cohort of PsA, excluding those with a history of trauma or cervical spine surgery. We calculated prevalence and incidence of AAS, and we used descriptive statistics to summarize and compare baseline demographic and disease-related characteristics between patients with and without AAS. Additionally, we used Cox regression with time-varying covariates to identify factors linked to AAS development and performed multivariable generalized estimating equations (GEE) analysis to assess associations with AAS.

Among 1535 patients with PsA, 34 (2.21%) were identified with AAS, including 20 at baseline and 14 during follow-up, with an incidence of 1.16 per 1000 person-years. Patients with AAS had higher rates of radiographic sacroiliitis (64.71%) and greater peripheral joint damage. Elevated erythrocyte sedimentation rate (ESR) was observed in 84.85% of cases. Cox regression identified radiographic sacroiliitis (hazard ratio [HR] 6.61, 95% CI 1.64-26.67) as the strongest predictor of AAS, whereas male sex was associated with a lower hazard (HR 0.25, 95% CI 0.07-0.89). In GEE analysis, radiographic sacroiliitis (odds ratio [OR] 3.64, 95% CI 1.61-8.24) and higher modified Steinbrocker scores (OR 1.01, 95% CI 1.00-1.02) were associated with AAS, whereas older age (OR 0.95, 95% CI 0.92-0.98) and male sex (OR 0.40, 95% CI 0.17-0.92) were associated with lower ORs.

AAS is an uncommon complication in PsA strongly associated with radiographic sacroiliitis and radiographic damage in peripheral joints.