Assessment of Facial Changes after Orthognathic Surgery Using Geometric Morphometrics

Abstract: Objectives:Orthognathic surgery results in significant changes in facial profile. Assessment of these changes is difficult due to inter-individual morphological variations. Therefore, Geometric morphometrics is a powerful tool to isolate surgery-induced changes from the normal variation among patients. Our aim in this research is to evaluate changes of the facial soft tissue after orthognathic surgery using geometric morphometrics analysis.Materials & Methods:This study included twenty-seven patients who underwent bilateral sagittal split ramus osteotomy (BSSRO), as a set back surgery. Two CT images were taken from each patient, the first was before surgery (T0), and the second was six months after surgery (T1). Twenty-seven CT images from volunteers with Skeletal Class I were also taken as the control. Three dimensional models were created in 3D modelling software (Mimics; Materialize). These models were imported into 3D surface analyzing software (HBM-Rugle; Medic Engineering) to perform geometric morphometrics analysis and conduct principal component analysis (PCA). PCA measurements were compared using ANOVA test as a statistical analysis.Result:Among fifteen principle components, there were significant differences between T0, T1 and control at the first and second principal components. The first principal component represented a variation in the lower anterior facial height, while the second principal component represented a variation in the anterior-posterior position of chin. The comparison between preoperative group and postoperative group clearly illustrated significant surgical effect of BSSRO among patients with Skeletal Class III. This effect is demonstrated by decrease of lower facial height, and movement of chin and lower lip area toward backward. The surgical effect of BSSRO was suboptimal when postoperative group was compared with control group.Conclusion: Although the patients who underwent BSSRO had significant improvement in the facial profile after surgery, the geometric morphometric analysis detected that additional procedures can be considered to obtain the optimal facial profile.