LAUSR

BACKGROUND The platysma is involved in the lower face movement, yet limited information on its functional role during perioral expressions can be found. OBJECTIVES The authors aimed to use 3-dimensional (3D) photogrammetry to analyze the platysma activity during expressions. METHODS Standardized frontal view 3D images were obtained from fifty-four volunteers. Three perioral expressions were analyzed: a full smile, mouth corner depression, and a grimace to show the lower teeth. Using the superimposed image subtraction technique, the positive volume change in the "heat map" of the neck skin surface was used as a sensitive indicator of platysma contraction. RESULTS During the three expressions, the proportion of platysma contraction was 42.6%, 75.9%, and 92.6%, respectively. We found platysma worked as a more critical dynamic force than expected. In most smiles involving the platysma, its upper portion contracted. With the laterally downward traction on the lower lip increasing, the upper and lower portions of the platysma contracted together and formed muscular bands. The platysma contracted extensively in the other two expressions. In some cases, platysma bands were observed by the vigorous contraction of muscle fibers. Besides, the platysma was found to be highly functionally active in young individuals. CONCLUSIONS This study introduced a simple method that could sensitively identify the functional status of the platysma. The results showed its highly active function in perioral expressions in young adults. It may assist surgeons in personalized decision-making toward platysma muscle-weakening strategies and work as an objective tool for the outcome evaluation.