Facial biomechanics: the standards of normal.

To quantify facial motor function during mimetic expressions, two new techniques were introduced in this study: linear measurement (LM) of skin landmarks and integrated electromyography (iEMG) of the facial musculature. Based on data from 30 normal subjects, three indices were derived to estimate total maximum motion, total maximum iEMG output, and the relationship between iEMG activity and motion. In three different facial expressions, plots of the logarithm of the iEMG value versus percent Displacement (pD) of skin landmarks had a high correlation (total mean r = 0.95). The normal LM and iEMG standards constitute a data base against which facial biomechanical properties in various pathologic states can be interpreted. In the course of data analysis, several interesting characteristics of facial function were identified.