Quantifying Synovial Enhancement of the Pediatric Temporomandibular Joint

Purpose: The purposes of this study were to assess a novel method for quantifying temporomandibular joint (TMJ) synovial enhancement on gadolinium-enhanced magnetic resonance imaging (MRI) and to establish normative values to allow early detection of synovitis. Materials and Methods: This is a retrospective cohort study of pediatric patients (aged 0 to 16 years) without jawpathology who underwent MRI scanswith contrast that included the TMJs. Froma coronal T1weighted image, the signal intensity within the superior and inferior joint spaces was divided by the signal intensity of the longus capitis muscle to establish a ratio by age. Intrarater reliability and inter-rater reliability were assessed. A mixed-model regression analysis was used to determine the 95% specificity threshold for normal ratios. Results: Temporal and optic nerve MRI scans of 158 patients were included. Normative synovial enhancement ratios (95% specificity) thresholds were established: 1.52, 1.68, and 1.55 for superior joint space, inferior joint space, and average of both joint spaces, respectively. Intrarater and inter-rater agreement was excellent. Conclusions: A ratio of signal intensity of the TMJ synovium to the longus capitis is a reliable method to quantify enhancement controlling for time after contrast infusion and may be useful for diagnosis of TMJ synovitis. (C) 2016 American Association of Oral and Maxillofacial Surgeons.