Contrast-enhanced magnetic resonance imaging (MRI) is commonly used to evaluate temporomandibular joint (TMJ) disease in patients with juvenile idiopathic arthritis (JIA). However, MRI assessments have been limited by qualitative reporting, the presence of enhancement in normal joints, and a lack of standardized protocols. The purpose of the present study was to compare a quantitative MRI analysis using an enhancement ratio (ER) to a new semiquantitative system developed by Outcome Measures in Rheumatology and Clinical Trials (OMERACT).
We performed a retrospective cross-sectional study of children with JIA who had undergone TMJ MRI with gadolinium enhancement at Boston Children's Hospital. The predictor variables were demographic data (sex, age at MRI) and disease-related findings (JIA subtype and arthritis medication at MRI). The outcome variables were OMERACT scores and ER (ratio of TMJ synovium and longus capitis muscle pixel intensities). The ER was compared with the OMERACT total, inflammatory, and damage scores using Pearson's correlation analysis and multivariable linear regression. Statistical significance was evaluated using the Student t test and analysis of variance with significance set at P < .05. Inter- and intraexaminer reliability were evaluated using intraclass correlation coefficients (ICCs).
The sample included 50 subjects (84% female) with a mean age of 12.7 ± 3.9 years and 124 MRI scans. The mean ER was 2.5 ± 0.9 (normal, <1.55). The mean OMERACT total was 4.9 ± 3.3. Controlling for age, sex, JIA subtype, and medication, for every 1-U increase in ER, the OMERACT increased by 3.11 for the total (P < .001), 1.01 for the inflammatory (P < .001), and 0.86 for the damage (P < .001) scores. The intra- and interrater consistency was better for the ER (ICC, 0.83 and 0.96, respectively) than for OMERACT (ICC, 0.77 and 0.35, respectively).
Quantitative evaluation of TMJ synovial enhancement using the ER is easier to score and has superior intra- and interrater agreement; however, it can only assess inflammation. Semiquantitative assessment of TMJ using the OMERACT adds data about chronic changes. Using both systems might provide the most accurate assessment of JIA status.