POS1323 SACROILIAC JOINT MRI ABNORMALITIES IN JUVENILE SPONDYLOARTHRITIS: AN UPDATE OF DEFINITIONS AND SCORING OF THE OMERACT JUVENILE IDIOPATHIC ARTHRITIS MRI SCORE
Authors: T. M. Otobo, N. Herregods, J. L. Jaremko, R. G. Lambert, I. Sudoł-Szopińska, A. B. Meyers, E. Kirkhus, P. Weiss, S. M. Tse, S. Appenzeller, P. G. Conaghan, D. G. Rumsey, J. Stimec, L. Jans, M. Van Rossum, N. Tzaribachev, J. Carrino, O. Papakonstantinou, M. Tolend, R. Moineddin, N. Haroon, W. P. Maksymowych, A. S. Doria
Journal: Annals of the Rheumatic Diseases (2021)

Background: Preliminary definitions for SIJ lesions in the OMERACT Juvenile Idiopathic Arthritis Magnetic Resonance Imaging score has been reported 1 . Investigators identified the need to revise the JAMRIS-SIJ item definitions. Objectives: To update the JAMRIS-SIJ definitions and scoring method. Methods: The OMERACT JAMRI working group was convened to discuss the performance of the score in a reliability exercise using 30 patients. Twenty investigators (12 radiologists, 8 rheumatologists) decided which definitions and scoring methods to be revised, retained or added. Results: The revised JAMRI-SIJ is in the Table 1. Table 1. Revised OMERACT JAMRIS-SIJ. Component Definition Segmentation/slice Score range/slice Bone Marrow Edema (BME) An ill-defined area of high bone marrow signal intensity within the subchondral bone in the ilium or sacrum on fluid sensitive images 4 quadrants/SIJ 0-8 BME Intensity Presence of hyperintensity of the marrow on fluid sensitive images using the signal of the presacral veins or cerebrospinal fluid as reference 1 score/SIJ 0-2 BME Depth Continuing increased signal on fluid sensitive images of depth ≥ 5mm/ ≥ 1cm from the articular surface using the signal of the presacral veins or cerebrospinal fluid as reference 1 score/SIJ 0-2 Osteitis An ill-defined area of high bone marrow signal intensity within the subchondral bone in the ilium or sacrum on contrast enhanced T1 weighted sequences 4 quadrants/SIJ 0-8 Capsulitis Increased signal on fluid sensitive or contrast enhanced T1 weighted sequences involving the superior portion of the SIJ capsule superior halves/SIJ 0-2 Joint space fluid High signal intensity equivalent to the CSF on fluid sensitive sequences within the joint space of the cartilaginous portion of the SIJ halves/SIJ 0-4 Joint space enhancement Increased signal intensity on contrast enhanced T1 weighted sequences within the joint space of the cartilaginous portion of the SIJ halves/SIJ 0-4 Inflammation in erosion cavity Increased signal intensity on fluid sensitive or contrast enhanced T1 weighted sequences in an erosion cavity of the cartilaginous portion of the SIJ halves/SIJ 0-4 Enthesitis Increased signal intensity in bone marrow and/or adjacent soft tissue on fluid sensitive or contrast enhanced T1 weighted sequences at sites where ligaments and tendons attach to a bone excluding retroarticular enthesitis Score per case 0-1 Damage Domain Sclerosis A substantially wider than normal area of very low bone marrow signal intensity within the subchondral bone in the ilium or sacrum on a non-fat suppressed sequence, preferably a non-fat suppressed T1 weighted sequence. This feature must also be present on all other sequences, as available 4 quadrants/SIJ 0-8 Erosion A focal loss of the low signal of cortical bone at the osteochondral interface and adjacent marrow matrix on T1 weighted images 4 quadrants/SIJ 0-8 Fat metaplasia lesion Homogeneous increased signal intensity within the subchondral bone marrow on T1weighted images 4 quadrants/SIJ 0-8 Backfill A high signal on non-contrast enhanced T1 weighted sequences in a typical location for an erosion, with signal intensity greater than normal bone marrow, clearly demarcated from adjacent bone marrow by an irregular band of low signal reflecting sclerosis at the border of the original erosion halves/SIJ 0-4 Ankylosis Presence of signal equivalent to regional bone marrow continuously bridging a portion of the joint space between the iliac and sacral bones halves/SIJ 0-4 Statement of overarching consideration for all definitions: “[…] in comparison to physiological changes normally seen on MRI examinations of age- and sex-matched children, and visible in 2 planes wherever available.” Conclusion: Revised JAMRIS-SIJ has been developed. Validation steps are underway. References: [1]Otobo TM, et al. Preliminary Definitions for Sacroiliac Joint Pathologies in the OMERACT Juvenile Idiopathic Arthritis Magnetic Resonance Imaging Score (OMERACT JAMRIS-SIJ). The Journal of rheumatology. 2019;46(9):1192-7. Acknowledgements: The authors acknowledge The Hospital for SickKids Research Trainee Competition (RESTRACOMP) and Queen Elizabeth II/Edward Dunlop Foundation Scholarship In Science and Technology (QEII-GSST) at the University of Toronto for funding provided to Dr. Tarimobo M. Otobo. The authors also acknowledge Prof. Dr. Desiree van der Heijde for providing expert commentary. Disclosure of Interests: None declared