Three-dimensional System of Analyzing Lip Movement

Aim: The aim of this study is to introduce our newly developed three-dimensional system of analyzing the lip movement using a video-based tracking system, and its preliminary clinical application.Materials and methods: Motions of black foamed styrol balls (10mm in diameter) placed on bilateral medial and distal canthal points, bilateral commissural points, and center point of the upper and lower lips, were tracked by two video cameras (Dejimo VCC-277) with a three-dimensional device for analyzing animation images (Dejimo D4202-01-T). After establishing the three-dimensional coordinate system using bilateral medial and distal canthal points to correct head motion, the lip movement was measured in these coordinates. Measurement reliability of this system was evaluated in comparison with values measured by a contact three-dimensional measuring unit (Mitsutoyo MXF203). For clinical application, during phonation of a long vowel/a/the lip movement was analyzed in 15 healthy adult subjects. The average standardized locus pattern of bilateral commissural points and center point of the lower lip was computed respectively. Based on this average standardized locus pattern, changes in the lip movement before and after orthognathic surgery were examined in two patients with facial asymmetry and mandibular protrusion.Results: The mean measurement reliability of this system was nearly 0.6mm in the X, Y, and Z axes, suggesting the mechanical accuracy. A marked deviation of the lip movement found in the affected commissural point and center point of the lower lip was improved in both patients after surgery. The amount of pre-operative deviation as well as that of post-operative improvement, was different in the two cases.Conclusion: Application of the method demonstrated clinical feasibility for the dynamic analysis of changes in lip movement after orthognathic surgery.