Frequency and Anatomic Distribution of Magnetic Resonance Imaging Features in the Sacroiliac Joints of Young Athletes

Objective Low grade bone marrow edema (BME) was reported in the sacroiliac joints (SIJ) of 25% of healthy individuals and mechanical back pain patients, challenging the imaging discrimination from early spondyloarthritis (SpA). It is unknown whether stress injury in competition sports may trigger BME. We explored frequency and anatomical distribution of SIJ MRI lesions in recreational and elite athletes. Methods After pre-test calibration, semicoronal SIJ MRI scans of 20 recreational runners (RR) before/after running and 22 elite ice-hockey players (IP) were assessed by 3 blinded readers for BME and structural lesions using an SIJ quadrant-based module. Scans of TNF-treated SpA patients served to mask readers. Readers recorded subjects meeting the ASAS definition for active sacroiliitis. Descriptive analysis comprised frequency of SIJ quadrants with BME/structural lesions and their distribution in 8 anatomical SIJ regions: upper/lower ilium and sacrum, subdivided in anterior/posterior slices, as concordantly recorded by ≥2/3 readers. Results The proportions in RR/IP fulfilling the ASAS definition concordantly by ≥2/3 readers were 30-35%/41%. The mean number (SD) of SIJ quadrants showing BME was 3.1 (4.2)/3.1 (4.5) in RR before/after running, and 3.6 (3.0) in IP. The posterior lower ilium was the single most affected SIJ region, followed by the anterior upper sacrum. Erosion was virtually absent. Conclusion In recreational and elite athletes, BME showed on average in 3-4 SIJ quadrants, meeting the ASAS definition in 30%-41%. The posterior lower ilium was the single most affected SIJ region. These findings in athletes help refine data-driven thresholds for defining sacroiliitis in early SpA. This article is protected by copyright. All rights reserved.