Three-dimensional assessment of facial asymmetry in Class III subjects. Part 1: a retrospective study evaluating postsurgical outcomes

Abstract

Objective: The present study aimed to determine the site and severity of maxillomandibular asymmetry before and after orthognathic surgery in asymmetric patients.

Materials and methods: Presurgery and postsurgery cone beam computed tomography (CBCT) data of 21 facial asymmetry patients (7 males and 14 females, mean age: 23.0 ± 3.36 years) with soft tissue chin deviation ≥ 3 mm who had undergone bimaxillary surgery were evaluated. Seven midline and twenty bilateral hard tissue landmarks were identified for the evaluation of facial asymmetry and outcomes were assessed against age- and gender-matched control subjects.

Results: In the asymmetry group, bilateral landmarks exhibited significant deviation in the mandible and midface regions. Before surgery, asymmetry was more severe at the mandibular midline and sites close to it, in the asymmetry group. Bimaxillary surgery proved to be highly effective, with a significant correction of the menton to a clinically normal value (2.90 mm, p < 0.001). After surgery, significant residual asymmetry was observed at the mental foramen (p = 0.001) in the R-L direction. Moreover, significant asymmetry persisted at the sigmoid notch (p = 0.001) in the S-I direction.

Conclusions: Mandibular midline landmarks and chin peripheral regions contribute significantly to overall facial asymmetry characteristics. Despite significant correction after bimaxillary surgery, asymmetry persisted at several sites, thereby requiring secondary correction. Comprehensive 3D presurgical planning is central for asymmetry correction in a single surgery.

Clinical relevance: The present study specifies the location of residual asymmetry sites and advocates the correction of those sites during initial surgery.

Keywords: Facial asymmetry; Maxillomandibular asymmetry 3D; Orthognathic surgery; Three-dimensional.

Fig. 1

3D view of the reference planes used. HP, horizontal plane (green)—passing through the orbitales (Or) and porion (Por). MSP, midsagittal plane (blue)—plane passing through nasion (Na) and sella (S), and perpendicular to HP. CP, coronal plane (purple)—plane passing through porion (Por) and perpendicular to the HP and MSP

Fig. 2

Representative images depicting the ROI for the registration of pre- and postoperative CBCT volumes based on the predefined stable structures of the cranium, where in pink signifies presurgery CBCT scan and blue signifies postsurgery CBCT scan. A, B, C ROI in axial, sagittal, and coronal views; D, E ROI in 3D reconstructed images (pre- and postsurgery respectively); F superimposed final 3D reconstructed image

Fig. 3

3D volume rendering of a skull showing various landmarks used in the study