Contrast-enhanced MRI compared to direct joint visualization at arthroscopy in pediatric patients with suspected temporomandibular joint synovitis

Background Contrast-enhanced magnetic resonance imaging (MRI) has become the gold standard when assessing the temporomandibular joint (TMJ) in children. To our knowledge, no previous pediatric study has compared findings of TMJ MRI with direct visualization of the joint using arthroscopy. Objective To determine if subjective findings on contrast-enhanced MRI of the temporomandibular joint correlate with arthroscopic findings of acute and chronic inflammation of the TMJ in children. Materials and methods Patients who had temporally related TMJ arthroscopy and contrast-enhanced TMJ MRI between March 2014 and March 2016 were identified. Imaging was retrospectively reviewed by two radiologists for erosions, condyle shape, bone marrow edema, effusion, severity of synovitis, joint space width measured in the coronal plane and enhancement ratio of the synovium relative to ipsilateral temporal lobe white matter. Joint space width was included because synovial thickening could widen the joint space. TMJ arthroscopy findings assessed included indicators of acute inflammation (active synovitis, number of joint sites affected, presence of retrodiscitis) and markers of chronic inflammation (hyperplastic synovitis, adhesions, disc perforation, chondromalacia). A Total Synovitis Score was given to all patients on arthroscopy, which multiplied the severity of active synovitis (0–4) with the number of joint recesses affected. Data were compared using the Fisher exact test and a P -value <0.05 was considered significant. Results There was no significant correlation between subjective synovitis on MRI and active synovitis on arthroscopy; however, there was a significant correlation between joint space width and hyperplastic synovitis ( P =0.04, 3.7 mm±0.8 vs. 2.9 mm±0.6) and a trend toward significance between subjective synovitis ( P =0.08) and enhancement ratio of synovium ( P =0.06) on MRI and hyperplastic synovitis on arthroscopy. Conclusion Joint space width and subjective synovitis on TMJ MRI correlate with arthroscopic findings of chronic synovitis. Increased joint space width may be useful when evaluating the TMJ with less time-intensive modalities, such as ultrasound. However, MRI findings did not correlate well with findings of acute inflammation on arthroscopy.