Anterior-posterior topographic patterns of thoracic joint structural abnormalities on chest CT in psoriatic arthritis.

OBJECTIVE: This study sought to develop and evaluate a chest computed tomography (CT)-based thoracic ring topographic framework for characterizing the anterior-posterior distribution of structural involvement in patients with psoriatic arthritis (PsA). METHODS: This retrospective study included 279 patients with PsA who underwent clinically indicated chest CT. The sternoclavicular joint (SCJ), costovertebral joint (CVJ), and costotransverse joint (CTJ) were assessed. A compartment was considered positive when its structural burden score exceeded 0 or any prespecified structural feature was present. Patients were classified as anterior-posterior (A-P) ring, posterior-only, negative, or anterior-only phenotypes. RESULTS: SCJ, CVJ, and CTJ positivity occurred in 131 (47.0%), 232 (83.2%), and 236 (84.6%) patients, respectively. All SCJ-positive patients were also positive at both posterior compartments, and no anterior-only phenotype was observed. The A-P ring, posterior-only, and negative groups comprised 131 (47.0%), 111 (39.8%), and 37 (13.3%) patients. Median total structural burden was 59.0, 40.0, and 0.0, respectively (P < 0.001). After adjustment, A-P ring involvement was associated with higher total burden than posterior-only involvement (β = 7.98, 95% CI: 3.42-12.54; P < 0.001), whereas the adjusted difference in posterior burden was not statistically significant (β = 4.45, 95% CI: -0.06 to 8.97; P = 0.053). CONCLUSION: SCJ positivity occurred within a combined anterior-posterior pattern and was associated with greater overall structural burden. Thoracic ring topography may provide a spatial framework that requires independent and multimodal validation.