The accuracy of sonography for evaluation of internal derangement of the temporomandibular joint in asymptomatic elementary school children: comparison with MR and CT.

BACKGROUND AND PURPOSE In order to clarify the incidence and evolution of disk displacement in the temporomandibular joint (TMJ) in children, we performed a longitudinal analysis in 18 subjects. Some investigators have suggested that sonography can provide information about the articular disk position of the TMJ. The purpose of this study was to determine the diagnostic accuracy of sonography for revealing internal derangement of the TMJ in elementary school children compared with our standard of reference, MR imaging and helical CT. METHODS Eighteen children were examined using both sonography and MR imaging or helical CT or both. The sonographically revealed distance between the articular capsule and the lateral surface of the mandibular condyle was measured and compared with that obtained by MR or helical CT scanning. RESULTS Compared with our MR/CT standard of reference, sonography revealed a sensitivity of 83%, a specificity of 96%, and an accuracy of 92% for identifying disk displacement (defined as a distance of 4 mm or more between the articular capsule and the lateral surface of the mandibular condyle). CONCLUSION Although sonography's sensitivity, specificity, and accuracy for the diagnosis of disk displacement were slightly inferior to those of MR or helical CT, we assert it is a useful imaging method for longitudinal investigations of a large group of elementary school children. Internal derangement of the TMJ should be suspected if sonography reveals a distance between the articular capsule and the lateral surface of the mandibular condyle of 4 mm or more.