Quantitative MRI evaluation of TMJ disc-condyle relationship

Objectives: to evaluate the disc mobility and quantify the disc-condyle relationship in normal temporomandibular joints (TMJs), using a graphic method to analyze magnetic resonance images. Methods: the articular relationship of 16 healthy TMJs in eight volunteers was investigated on a sagittal plane during standardized mouth opening. The method was based on a coordinate system which located the center of the condylar process and divided the total surface (TS) of the disc section into the anterior surface (AS) and posterior surface (PS). The hypothesis was that AS/TS ratio characterized the disc-condyle relationship. Results: the mean AS/TS ratio was 0.5 (sd= 0.09) in closed mout position and 0.36 (sd = 0.13) at 25 mm mouth opening. Using the Bland-Altman plot, the data showed a significant intra observer reproducibility and a significant inter observer agreement, at the 5 per cent significance level. Conclusion: AS/TS ratio may quantify a normal TMJs disc-condyle relationship and assess the ability of the disc to move, but further studies are required to establish range of normal values.