Application and preliminary validation of the hip inflammation MRI scoring system (HIMRISS) in spondyloarthritis

Spondyloarthritis (SpA) is an inflammatory rheumatic disease and hip involvement often results in severe deformities and functional impairment. Magnetic resonance imaging (MRI) is a powerful imaging tool for detecting early hip lesions in SpA. The aims of this study are to apply the hip inflammation MRI scoring system (HIMRISS) in SpA patients and to evaluate its reproducibility and validity.

Four readers new to HIMRISS (two radiologists and two rheumatologists) scored the MRI scans obtained from a total of 55 SpA patients with hip lesions in two separate exercises (33 patients in exercise 1 and 22 patients in exercise 2). After the training and review process for exercise 1, these well-trained readers with expertise in the HIMRISS method scored the scans obtained from 22 patients and evaluated the association between HIMRISS and clinical activity of SpA, including Ankylosing Spondylitis Disease Activity Score (ASDAS), laboratory features, Bath Ankylosing Spondylitis Disease Activity Index and Harris hip scores.

HIMRISS is a reliable MRI scoring method for bone merrow lesions (BML) and synovitis in SpA. After 2 training exercises, the reliability improved from 0.67 to 0.90. The reliability for detecting femoral BML, acetabular BML, and synovitis effusion was very good after the 2 exercises (overall intraclass correlation coefficient = 0.73, 0.84 and 0.88, respectively). The clinical correlations between HIMRISS and ASDAS were most significant, and the correlations were closer to summed bilateral HIMRISS scores than just the worse side. HIMRISS was found to be an excellent tool for the early diagnosis of inflammation before the occurrence of structural damage, which was not significantly reflected in the systemic diagnosis.

HIMRISS offers a reliable MRI scoring method for hip joint in SpA, and it is beneficial for early detection and fast quantification in disease activity assessment.