Error patterns and observer variations in the high-resolution ultrasonography imaging evaluation of the disk position of the temporomandibular joint

OBJECTIVES. The purpose of this study was (1) to describe errors in the interpretation of high-resolution ultrasonography (HR-US) images of the temporomandibular joint (TMJ) and analyze the discrepancies between HR-US imaging and diagnostic magnetic resonance imaging findings, and (2) to measure interobserver and intraobserver variations with respect to reporting HR-US images of the TMJ. STUDY DESIGN. The sonographic reports of 208 patients aged 13 to 78 years who had a prospective clinical diagnosis of TMJ internal derangement were correlated with magnetic resonance imaging results. Prospective and retrospective readings were used to classify types of disk displacement. Assessment of observer variation was based on a set of 200 HR-US images in 50 randomly selected patients. The images were interpreted independently by 2 trained radiologists at 2 sessions, 1 to 2 weeks apart. RESULTS. Prospective interpretation of TMJ HR-US images at the closed-mouth position had a sensitivity of 80%, specificity of 87%, and accuracy of 82%. For images at the maximum mouth-opening position, the sensitivity was 68%, specificity 93%, and accuracy 82%. The number of diagnostic errors at retrospective analysis was 60.3% (n = 73) of the number at prospective analysis. The intraobserver agreement for reporting the disk position at the closed-mouth position was 93% and at the maximum mouth-opening position was 88%. The agreement between the 2 observers was 89% on the position of the disk at the closed-mouth position and 84% at the maximum mouth-opening position. CONCLUSIONS. The high diagnostic accuracy, together with the low observer variation reported in this study, suggest that HR-US of the TMJ is a valuable imaging technique for assessment of disk displacement. Many errors that occur at prospective analysis didn't occur at retrospective analysis.