Measurement of anterior translation of the mandibular condyle using sonography

[Purpose] To establish a standardized sonographic approach to quantify anterior translation of the mandibular condyle during mouth opening by examining the reliability of image acquisition and processing, and to understand how anterior condylar translation contributes to mouth opening. [Participants and Methods] Twenty-eight participants without temporomandibular disorder (TMD) participated. During day 1 of data collection, all participants performed maximal mouth opening while an examiner recorded anterior condylar translation using sonography. The mouth opening range of motion was also obtained. On day 2 of data collection, the same procedure was performed on 6 participants that participated in day 1 of data collection. To establish reliability of image processing, 3 examiners measured condylar translations on 2 separate days. To determine reliability of image acquisition, images obtained from 2 days of data collection were analyzed. [Results] Excellent intra-class correlation coefficients (ICCs) and small standard errors of measurement (SEMs) for image acquisition and processing were shown. A significant, linear model was found to describe the relationship between condylar anterior translations and mouth opening. [Conclusion] Anterior condylar translation during mouth opening can be reliably measured using sonography. The linear relation between condylar motion and mouth opening can be used to guide clinical practices.