The clinical application of three dimensional motion capture (4d): a novel approach to quantify the dynamics of facial animations

Abstract

The aim of this study was to evaluate the feasibility of measuring the change in magnitude, speed and motion similarity of facial animations in head and neck oncology patients, before and after lip split mandibulotomy. Seven subjects (4 men, 3 women; age range 42–80 years) were recruited from a multidisciplinary cancer treatment clinic. All patients were planned for the resection of the oral and oro-pharyngeal cancer via a lower lip-split mandibulotomy access procedure. The subjects were asked to perform four facial animations (maximal smile, lip purse, cheek puff and grimace) from rest to maximal position both before and 8–10 weeks following surgery. The animations were captured using a Di4D motion capture system which recorded 60 frames per second. Nine facial soft tissue landmarks were manually digitized on the first frame of the three dimensional image of each animation by the same operator and automatically tracked for rest of the sequential frames. The intra-operator digitization error was within 0.4 mm. Lip purse and maximal smile animation showed the least amount of change in magnitude (0.2 mm) following surgery, speed difference was least for maximal smile animation (−0.1 mm/s). Motion similarity was found to be highest for lip purse animation (0.77). The study confirmed that the surgery did influence the dynamics of facial animations and Di4D capture system can be regarded as a feasible objective tool for assessing the impact of surgical interventions on facial soft tissue movements. A larger sample and multicenter investigations can improve the understanding of how various surgical procedures affect the dynamics of facial animation.