OBJECTIVE: To test the impact of inflammation on MRI-structural changes occurring in the sacroiliac joints (SIJ) and the spine.
METHODS: Patients with early axSpA from the DESIR cohort were included. MRIs of the SIJ (MRI-SIJ) and spine (MRI-spine), obtained at baseline, 2 and 5 years, were scored by 3 central readers. Inflammation and structural damage on MRI-SIJ/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-SIJ/MRI-spine) on damage (MRI-SIJ/MRI-spine, respectively) was evaluated in two models: i. Baseline prediction model: effect of baseline inflammation on damage assessed at 5-year; and ii. Longitudinal model: effect of inflammation on structural damage assessed during 5 years.
RESULTS: 202 patients were included. Both the presence of bone marrow edema (BME) on MRI-SIJ and on MRI-spine at baseline were predictive of 5-year damage (≥3 fatty lesions) on MRI-SIJ [OR=4.2 (95% CI: 2.4; 7.3)] and MRI-spine [OR=10.7 (95% CI: 2.4; 49.0)], respectively, when adjusted for CRP. The association was also confirmed in longitudinal models (when adjusted for ASDAS) both in the SIJ [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-SIJ 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 MRI-inflammation and several types of MRI-structural damage in patients with early axSpA which adds to the proof for a causal relationship.