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Background Inflammation shown on MRI of the sacroiliac joint (MRI-SI) is prevalent in axSpA (±30%) but the specificity is not well known. Objectives To compare MRI of the sacroiliac joints (MRI-SI) of healthy, symptomless individuals and those with known mechanical strain acting upon SI joints to axial spondyloarthritis (axSpA) and chronic back pain (CBP) patients. Methods Three trained, calibrated and blinded readers randomly scored MRI-SI of 172 subjects: 47 healthy individuals without current/past back pain(; 1 47 axSpA patients from the SPondyloArthritis Caught Early (SPACE) cohort (with a previously confirmed positive MRI-SI); 47 CBP controls (irrespective of MRI-SI results) from the SPACE cohort; 7 women with postpartum back pain; and 24 frequent runners. Readers scored according to the ASAS definition and SPARCC score. Results Of the 47 healthy volunteers, 11 (23.4%) had a positive MRI-SI, compared to 43 of 47 (91.5%) positive axSpA patients and 3 of 47 (6.4%) CBP patients. Of the runners, 3 of 24 (12.5%) and of the women with postpartum back pain 4 of 7 (57.1%) had a positive MRI-SI. Using a SPARCC cut-off of ≥2 for positivity, 12/47 and healthy volunteers (25.5%), 46/47 positive axSpA patients (97.9%), 5/47 CBP controls (10.6%), 4/24 runners (16.7%) and 4/7 women with postpartum back pain (57.1%) were positive. ‘Deep’ BME-lesions were not found in healthy volunteers, CBP patients and runners, but in 38 of 47 positive axSpA patients (80.9%) and in 1 of 7 women with postpartum back pain (14.3%). Conclusions A substantial proportion of healthy individuals without current/past back pain has a positive MRI-SI according to the ASAS definition. Deep (extensive) BME lesions are exclusively found in axSpA patients. Reference [1] van Hoeven L, Luime JJ, et al. Bone marrow edema and structural lesions in the sacroiliac joint in a large cohort of patients with axial spondyloarthritis, chronic low back pain and healthy controls. ACR Annu Meet 2013;2889. Disclosure of Interest None declared |
