Clinical predictability of temporomandibular joint disc displacement

Single items from a typical clinical examination have proved disappointing in their predictive value for temporomandibular joint (TMJ) disc displaceme nt. Only one criterion (the 12 o'clock) is used to diagnose normal disc pos ition. According to this criterion, the posterior band of the disc should b e located at the top of the condyle, at the 12 o'clock position. The purpos e of this study was to determine which signs and symptoms provide a valid p rediction of the condition of the joint based on 4 magnetic resonance imagi ng (MRI) criteria used to define normal disc position. Sagittal MRI and cli nical findings of 137 temporomandibular disorder patients and 23 normal asy mptomatic volunteers were used. Three calibrated and blinded observers inte rpreted the images. Disc position with the mouth closed was evaluated based on 4 MRI criteria: 12, 11, 10 o'clock, and the intermediate zone. Disc pos ition with the mouth open was determined based on one criterion. It was con sidered normal if the intermediate zone of the disc was located between the condyle and the articular eminence. Joints were classified as normal or as having disc displacement with or without reduction. The sensitivity and sp ecificity of multiple clinical parameters for predicting the condition of t he joint established by each of these 4 gold-standard MRI criteria were the n determined. Regarding disc displacement with reduction, significant diffe rences were observed in the sensitivity and specificity of all of the clini cal parameters used to predict the imaging diagnosis established by each of the criteria. Concerning disc displacement without reduction, no significa nt differences were observed. The intermediate zone criterion was the crite rion that most accurately reflected the condition of the joint. The clinica l predictability of the disorder diagnosed according to this criterion sugg ests that clinical findings alone are too often nonspecific as predictors o f the imaging stage of disc displacement. However, we found that combining the most sensitive clinical items to predict the disorder and using an over all criterion for positivity to interpret the results led to an impressive increase in the specificity of the combination, enabling false-positive dia gnoses to be excluded.