Session Type: Poster Session (Sunday)
Session Time: 9:00AM-11:00AM
Background/Purpose: Bone marrow edema (BME), fat metaplasia (FL) and erosions are relevant for magnetic resonance imaging (MRI) changes in the sacroiliac joints (SIJ) in axial spondyloarthritis (axSpA). However, MRI changes have recently also been reported in subjects with no axSpA (1,2). We mapped MRI lesions suspicious of axSpA in patients diagnosed with axSpA and compared them to patients with chronic back pain (cBP, non-SpA).
Methods: Consecutive patients with cBP< 45 years were included with at least one pathologic lesion (any type) in SIJ-MRIs performed during cBP symptoms. AxSpA patients diagnosed by 2 experienced rheumatologists in consensus also had to fulfil ASAS classification criteria. Two experienced readers, blinded for patient´s information) evaluated all MRIs independently. Lesions were only counted positive if readers were in agreement. Both coronal (assessing upper and lower sacral and iliac SIJ) and axial (assessing ventral, middle and retroauricular) MRI orientations were analyzed for localization of BME, FL, sclerosis and erosions. In addition, length and width were digitally measured for BME, FL and sclerosis, and signal intensity was measured in each individual patient (no units). Mann-Whitney-U-test was applied for patients classified as positive by both readers for respective lesions.
Results: 200 consecutive patients (100 axSpA, 100 non-SpA), mean age 36.1±11.3 and 40.3±11.0 years, respectively, were analyzed. BME was found in 85% vs. 80% patients, while 80% vs. 69% had FL, 54% vs. 40% had sclerosis and 64% vs. 12% had erosions, respectively. The largest surface area covered by BME in axSpA vs. non-SpA was found in lower and dorsal SIJ: 60±10.1mm3 in the iliac and 47.3±9.4mm3 in sacral part vs. upper and ventral SIJ: 18.7±3.4mm3 in sacral and 5.2±0.1 mm3 in the iliac part. AxSpA-patients showed larger surface area covered by FL in upper and anterior sacral SIJ (305.5±56.3 mm3), whereas non-SpA-patients showed larger FL areas in lower and posterior sacral SIJ (197.9±1.2 mm3). Upper and anterior iliac part larger sclerosis involvement in both SpA (139.3±11.6 mm3) and non-SpA (81.8±2.8 mm3). Mean signal intensity of all lesions and MRI planes differed between axSpA (102.385) and non-SpA (48.995) patients for BME (p< 0.001) but not for FL. AxSpA patients had significantly more SIJ quadrants with pathologic changes, except for BME and sclerosis in ventral and fat in retroauricular SIJ-part. Erosions in the mid (61 vs. 7) and the ventral (51 vs. 8) part of the SIJ could discriminate best between axSpA and non-SpA (both p< 0.001).
Conclusion: Although all lesion types may be found in both groups, the anatomic pattern of SIJ involvement can still distinguish axSpA from non-SpA. The most frequently involved sites were not necessarily also the best differentiating sites. The localization and morphological appearance of SIJ-MRI features suggestive of axSpA may serve as an additional feature in the definition of a ‘positive’ MRI both for diagnosis and classification.
(1) Weber U et al. Arthritis Rheumatol 2018
(2) De Winter et al. Arthritis Rheumatol 2018
To cite this abstract in AMA style:Baraliakos X, tomaschoff j, Fruth M, Braun J. Localization and Morphology of Magnetic Resonance Imaging Features of Pathologic Changes in the Sacroiliac Joints Suggestive of Axial Spondyloarthritis – a Systematic Comparison of Patients and Controls with Chronic Back Pain [abstract]. Arthritis Rheumatol. 2019; 71 (suppl 10). https://acrabstracts.org/abstract/localization-and-morphology-of-magnetic-resonance-imaging-features-of-pathologic-changes-in-the-sacroiliac-joints-suggestive-of-axial-spondyloarthritis-a-systematic-comparison-of-patients-an/. Accessed November 29, 2020.
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