Three-dimensional evaluation of facial asymmetry in patients with hemifacial microsomia using stereophotogrammetry

Purpose: To quantify the surface facial asymmetry in a group of young patients with hemifacial microsomia (HFM) and to investigate differences with a homogeneous sample of healthy subjects, using a novel stereophotogrammetric method. Materials and methods: Twelve patients (mean age 13.1 ± 3.1 years) with different degrees of HFM and 15 healthy controls (mean age 12.2 ± 3.5 years) were imaged with a stereophotogrammetric facial scanner. The root mean square error (RMSE) of the distances between the corresponding points of each original photograph and its mirror copy was calculated for the whole face and for each trigeminal third, as defined by the innervation of trigeminal branches. A statistical analysis was performed to compare the RMSE value of all facial areas within each group and between patients and controls. Results: RMSE values progressively increased from the upper to the lower third of face, both in patients and controls. The level of asymmetry was significantly higher in HFM subjects for middle third (p < 0.01), lower third (p < 0.001) and whole face (p < 0.001); no statistically significant differences were found between the groups for the upper third. Conclusions: The reported technique provides an accurate topographic analysis of the facial asymmetry, and is recommended for conditions such as HFM affecting only part of the face.