Objective: Two-jaw surgery is often performed in patients with facial asymmetry to improve malocclusion and facial esthetics. However, undesired changes of the nasal morphology may collaterally occur due to repositioning of the maxillary bone. The purpose of this study was to investigate the influence of two-jaw surgery on nasal morphology in orthognathic patients with facial asymmetry using 3-dimensional computed tomography (3D-CT) image analysis.
Materials and Methods: Twelve patients (7 females and 5 males, mean age at the time of surgery: 24.3±5.9 years) with facial asymmetry who had undergone two-jaw surgery were enrolled. Pre-surgical facial 3D-CT images (T1) were superimposed on images obtained 4 months post-surgery (T2) using 3D imaging software. The 3D coordinate system constructed by Frankfurt horizontal (FH) plane was used for the analysis, including the frontal plane, incorporating orbits on both sides, and the sagittal plane, intersecting at the midpoint between the orbits. After superimposing the T1 and T2 images, soft-tissue 3D-CT images were reconstructed, and changes in external nasal morphology were analyzed. Furthermore, linear and angular measurements of hard and soft tissues, as well as measurements of the external nasal aperture area were obtained and compared between T1 and T2.
Results: T2 images showed anterior placement of nasal area soft tissues resulting in widening of the nasal wing, and a significant reduction in canting of the alar base and the lip. The external nasal aperture area was similar between the shifted and non-shifted sides at T1. At T2, the nasal aperture was significantly increased in both the shifted and non-shifted sides, but the aspect of change was the same. Positive correlations were seen between the horizontal/vertical movement of ANS and nasal soft tissues, and between the cant of the occlusal plane and the alar base.
Conclusion: The study showed that two-jaw surgery is an effective treatment modality for patients with facial asymmetry. However, since nasal area soft tissues were correlated with movement of ANS, the effect of maxillary movement on nasal soft tissues must be considered when making the treatment plan.
