High-Resolution Sonographic Measurement of Normal Temporomandibular Joint and Masseter Muscle

ObjectiveThe purpose of this study was to measure the width of the temporomandibular (TM) joint capsule and the thickness of the masseter muscle (MM), with high resolution ultrasound in patients without TM-joint-associated diseases.MethodsFrom April 8, 2011 to June 10, 2011, 42 patients without TM disorders were recruited and examined with a real-time 12-MHz linear-array scanner. The maximum thickness of capsular width of the TM joint was measured in the closed mouth position. The thickness of MM was also measured at both rest and maximum contraction.ResultsA total of 84 joints were included. The mean (± standard deviation) TM joint capsular width was 1.9 ± 0.4 mm; MM thickness at rest was 9.0 ± 1.9 mm; and MM thickness during occlusion on maximal force was 11.8 ± 2.8 mm with an increased ratio of 33 ± 25%. No significant differences were found with regard to the laterality in TM joint capsular width, MM thickness at rest and during maximal occlusion, or augmented MM thickness ratio. There was no difference in the increased ratio of MM between sex, however, the MM thickness at rest and during maximal occlusion was greater in male than in female patients.ConclusionHigh-resolution ultrasound is an alternative noninvasive method for the evaluation of the TM joint. Sex should be considered in clinical judgment for evaluating MM thickness.