Quantification of the three-dimensional displacement of normal facial movement.

This study was undertaken to quantify 3-dimensional (3-D) facial movement in normal subjects, and to identify the individual axes in which this movement occurred. Displacement data on 42 subjects were collected and analyzed with the Expert Vision Motion Analysis System. The 3-D displacement was calculated by vectorially subtracting maximum marker movement from previously identified reference marker points. The 3-D range of normal facial movement was quantified, with the greatest displacement occurring during maximum smile. When the individual axes were examined, we found that most movement occurred in the vertical axes for the majority of expressions, followed by the anterior-posterior axis. These results may create an objective baseline from which disorders of the facial nerve, and hence, medical, surgical, and physiotherapy treatment interventions, can be analyzed in the future.