Augmented Reality to Evaluate Temporo-Mandibular Joint Alterations in Orthognathic Patients

Augmented Reality (AR) is a technology that offers the possibility to overlap virtual objects on the real scene. In recent years, AR has been proposed and applied also in the medical field. In this study, we aimed to develop an AR application for Microsoft HoloLens 2 to be used for the evaluation of temporomandibular joint (TMJ) alterations in orthognathic patients. The actual procedures to diagnose TMJ alterations consist of direct palpation of the joint and/or execution of kinesiographic exam which allows to record the jaw movements. The developed AR application provides the projection of the reconstructed virtual underlying bony structures directly on the visible patient's head, thus facilitating the diagnostic evaluation of the surgeon. The AR application was tested on a volunteer during TMJ tasks of opening and closing of the mouth. During the tasks, video recordings were taken from the HoloLens cameras, and then they were processed by Matlab to derive the kinematic curves and values describing the jaw movements. The AR-derived TMJ trajectories were then compared with standard kinesiographic acquisitions. The results demonstrated a good match between the AR-derived kinematics and kinesiographic curves. Future improvements are needed for the tracking modalities to allow more accurate quantification of the TMJ kinematics in the frontal view.