Purpose or Case Report: Clinical assessment of the Sacroiliac Joint (SIJ) is limited due to the location and anatomy of the joint. Magnetic Resonance Imaging is a sensitive, non- invasive tool in detecting early SIJ inflammatory changes and structural damage in Juvenile Idiopathic Arthritis (JIA). The quantification of interval change of pediatric SIJs using MRI based scoring methods will serve as an important objective outcome measure for the assessment of disease severity and treatment effectiveness in JIA.
Methods & Materials: The OMERACT consensus-driven methodology consisting of iterative surveys and focus group meetings within an international group of pediatric rheumatologists and radiologist was utilized to decide the measurement construct, items, and definitions. Consensus was deemed to have been achieved if greater than 70% agreement was reached among voting attendees at the session in the absence of greater than 15% present or more in strong disagreement.

Results: Twenty-eight international multidisciplinary experts from North America, Europe, South Asia and South America participated in the study. Two domains, inflammation and structural, were identified. Definitions for bone marrow edema, joint space inflammation, capsulitis, and enthesitis were derived for joint inflammation; sclerosis, erosion, fatty lesion and ankylosis were defined for assessing structural joint changes.

Conclusions: Preliminary consensus-driven definitions for inflammation and structural elements have been drafted, underpinning the ongoing development of the Juvenile arthritis MRI scoring system for SIJ (JAMRIS-SIJ).