What are the Surgical Movements in Orthognathic Surgery That Most Affect the Upper Airways? A Three-Dimensional Analysis

Abstract

Purpose: Most studies have focused on airway changes after maxillomandibular advancement; however, airway size will change depending on the type, direction, and magnitude of each skeletal movement. The aim of this study was to assess the effect of the maxillary and/or mandibular movements on the pharyngeal airway volume and the minimum cross-sectional area using 3-dimensional cone-beam computed tomography voxel-based superimposition.

Patients and methods: The investigators designed and implemented a retrospective cohort study composed of patients with dentofacial deformity subjected to orthognathic surgery. The predictor variables were the surgical movements performed at surgery. The primary outcome variables were the pharyngeal airway volume and minimum cross-sectional area measured preoperatively, at 1- and 12-month follow-up. Skeletal and volumetric relapse and stability were recorded as secondary outcomes at 1 and 12 months, respectively. Descriptive, bivariate and correlation analyses were computed. Significance was set at P < .05.

Results: The sample was composed of 103 patients grouped as follows: bimaxillary (53), maxillary (25), or isolated mandible (25). All of the surgical treatments resulted in a significant linear pattern of initial immediate increase of 33.4% (95% confidence interval [CI]: 28.2 to 38.7%; P < .001) in volumetric (nasopharynx [28.7%, CI: 22.7 34.9%; P < .001], oropharynx [36.2%, CI: 29.0 to 43.5%; P < .001], and hypopharynx [31.5%, CI: 25.7 to 37.3%; P < .001]) and minimum cross-sectional area parameters (bimaxillary = 104%, [CI: 87.1 to 122.1%; P < .001], maxillary = 39.5%, [CI: 18.4 to 60.7%; P < .05], and mandible = 65.8%, [CI: 48.1 to 83.6%; P < .05]), followed by a slight downward trend (stabilization) at 12-month follow-up. Airway increase was favored by mandibular advancement (P < .05) and mandibular occlusal plane changes by counterclockwise rotation (P < .05).

Conclusions: The results of this study suggest that there is a favorable effect of orthognathic surgery in the upper airway regardless of the surgical approach, with bimaxillary advancement and mandibular occlusal plane changes by counterclockwise rotation being the most significant contributors.