THU0541 ANATOMICAL LOCATION OF SACROILIAC JOINT MRI LESIONS IN PATIENTS WITH AXIAL SPONDYLOARTHRITIS, POSTPARTUM WOMEN, PATIENTS WITH DISC HERNIATION, CLEANING STAFF, RUNNERS AND HEALTHY PERSONS

Background: Bone marrow edema (BME) on sacroiliac joint (SIJ) MRI is central in the Assessment of SpondyloArthritis International Society classification criteria for axial spondyloarthritis (axSpA). However, BME can be seen in other conditions and healthy persons. The presence of structural lesions may contribute to diagnosing axSpA. Objectives: To investigate the location and distribution of SIJ MRI lesions in patients with axSpA and disc herniation, women with and without post-partum pain (PPP), cleaning staff, runners, and healthy persons. Methods: In a prospective cross-sectional study of 204 participants, MRI of the SIJs was evaluated by two readers. MRI images were scored according to the SPARCC SIJ Inflammation1 and Structural (SSS)2 lesion definitions. Based on concordant reads, lesions were analysed according to location (unilateral/bilateral SIJ, upper/lower sacral/iliac quadrant/joint half, anterior (slice1-3)/central (slice 4-6)/posterior (slice 7-9) SIJ sections. Results: BME was present in nearly all groups, in all quadrants, and primarily in the anterior SIJ section (Figure 1), but rarely as a bilateral feature, except in axSpA and women with PPP (Table 1). Fat lesion (FAT) was mainly found in axSpA, in all slices, and mostly bilaterally in the sacrum. In the other groups FAT was primarily located in the anterior and central SIJ sections. Sclerosis was only seen in the ilium, and was present in most groups, particularly in women with PPP, often bilaterally. Erosion was only seen in women with PPP (mostly unilaterally) and in axSpA (mainly bilaterally in the ilium). Backfill and ankylosis were only seen in axSpA. Conclusion: Typical locations of common SIJ lesions in axSpA and non-axSpA were reported. In non-axSpA, except women with PPP, bilateral as well as posterior lesions were rare, while backfill and ankylosis were absent. References: [1]Maksymowych et al, Arthritis Rheum, 2005 [2]Maksymowych et al, J of Rheumatol, 2015 Acknowledgments: Disclosure of Interests: Sengul Seven Grant/research support from: Novartis, Mikkel Ǿstergaard Grant/research support from: AbbVie, Bristol-Myers Squibb, Celgene, Merck, and Novartis, Consultant of: AbbVie, Bristol-Myers Squibb, Boehringer Ingelheim, Celgene, Eli Lilly, Hospira, Janssen, Merck, Novartis, Novo Nordisk, Orion, Pfizer, Regeneron, Roche, Sandoz, Sanofi, and UCB, Speakers bureau: AbbVie, Bristol-Myers Squibb, Boehringer Ingelheim, Celgene, Eli Lilly, Hospira, Janssen, Merck, Novartis, Novo Nordisk, Orion, Pfizer, Regeneron, Roche, Sandoz, Sanofi, and UCB, Lone Morsel-Carlsen: None declared, Inge Juul Sorensen: None declared, Birthe Bonde: None declared, Gorm Thamsborg: None declared, Jens Jorgen Lykkegaard: None declared, Susanne Juhl Pedersen Grant/research support from: Novartis