Inflammation of the Sacroiliac Joints and Spine and Structural Changes on Magnetic Resonance Imaging in Axial Spondyloarthritis: Five‐Year Data From the DESIR Cohort

OBJECTIVE: To test the impact of inflammation on structural changes occurring in the sacroiliac (SI) joints and the spine detected on magnetic resonance imaging (MRI). METHODS: Patients with early axial spondyloarthritis (SpA) from the Devenir des Spondylarthropathies Indifferérenciées Récentes (DESIR) cohort were included. MRIs of the SI joints (MRI‐SI joints) and spine (MRI‐spine), obtained at baseline, 2 years, and 5 years, were scored by 3 central readers. Inflammation and structural damage on MRI‐SI joints and MRI‐spine were defined by the agreement of ≥2 of 3 readers (binary outcomes) and by the average of 3 readers (continuous outcomes). The effect of inflammation (MRI‐SI joints/MRI‐spine) on damage (MRI‐SI joints/MRI‐spine, respectively) was evaluated in 2 models: 1) a baseline prediction model (the effect of baseline inflammation on damage assessed at 5 years); and 2) a longitudinal model (the effect of inflammation on structural damage assessed during a 5‐year period). RESULTS: A total of 202 patients were included. Both the presence of bone marrow edema on MRI‐SI joints and on MRI‐spine at baseline were predictive of 5‐year damage (≥3 fatty lesions) on MRI‐SI joints (odds ratio [OR] 4.2 [95% confidence interval (95% CI) 2.4, 7.3]) and MRI‐spine (OR 10.7 [95% CI 2.4, 49.0]), respectively, when adjusted for C‐reactive protein level. The association was also confirmed in longitudinal models (when adjusted for Ankylosing Spondylitis Disease Activity Score) both in the SI joints (OR 5.1 [95% CI 2.7, 9.6]) and spine (OR 15.6 [95% CI 4.8, 50.3]). Analysis of other structural outcomes (i.e., erosions) on MRI‐SI joints yielded similar results. In the spine, a significant association was found for fatty lesions but not for erosions and bone spurs, which occurred infrequently over time. CONCLUSION: We found a predictive and longitudinal association between inflammation detected on MRI and several types of structural damage detected on MRI in patients with early axial SpA, which adds to the evidence for a causal relationship.