POS0973 INFLUENCE OF ANATOMICAL VARIATION OF THE SACROILIAC JOINTS ON INFLAMMATORY LESIONS ON MAGNETIC RESONANCE IMAGING

Abstract

BackgroundAnatomical variation of the sacroiliac (SI) joints is more common among patients with LBP than healthy controls; increased biomechanical strain to the joint may play a role in axial spondyloarthritis (axSpA).ObjectivesTo assess the association of lesions joint shape variation on inflammatory lesions on SI joint magnetic resonance imaging (MRI) in patients with axSpA.MethodsIn this post-hoc analysis a total of 684 patients from four different prospective cohorts were evaluated (379 axSpA). Two readers independently scored all patients for joint form, erosion, sclerosis, fat metaplasia and bone marrow edema (BME). Logistic regression analyses were used to assess the association of lesions on imaging joint form; this analysis was performed separately for axSpA patients and controls.ResultsTypical joints were observed in 56.5% of axSpA patients (200/354) and 55.7% of control patients (169/303); in axSpA patients exhibited a significantly higher proportion of intra-articular variants (18.4% vs. 11.6%; p<0.001) and crescent joint shapes (11.0% vs. 5.3.%; p<0.001) than controls. AxSpA patients with intraarticular joint form variants had increased odds for erosions (OR 2.09; 95%CI 1.18-3.69) and BME (OR 1.79; 95%CI 1.13-2.82); this association was not seen in controls. Accessory joints increased the odds for sclerosis in axSpA patients (OR 2.54;95%CI 1.10-5.84) and for BME (2.05; 95%CI 1.03-4.07) and sclerosis (OR 17.91; 95%CI 6.92-46.37) in controls.ConclusionJoint form variations are associated with inflammatory lesions on SI joint MRI of axSpA patients but not controls; this indicates a role for atypical joint forms in sacroiliitis.