Upper airway changes after orthognathic surgery in patients with skeletal class III high-angle malocclusion and mandibular deviation.

Objectives: This study analyzed the differences in the upper airway of patients with skeletal Class III high-angle malocclusion with and without mandibular deviation, and further investigated whether there are differences in the changes in upper airway space after orthognathic surgery between the two groups.

Materials and methods: 15 patients with skeletal Class III high-angle malocclusion and mandibular deviation, and 15 patients without mandibular deviation were selected to explore the impact of mandibular deviation on the upper airway. Additionally, 16 patients with mandibular deviation undergoing orthodontic-orthognathic combined treatment, and 13 patients without mandibular deviation, were selected to investigate the differences in the changes in upper airway space after orthognathic surgery between the two groups.

Results: In patients with skeletal Class III high-angle malocclusion, the deviation group showed significantly smaller sagittal diameter/maximum transverse diameter, cross-sectional area, volumes of oropharynx and hypopharynx, and total volume compared to the normal group, with all differences being statistically significant. After orthognathic surgery, the postoperative sagittal diameter/maximum transverse diameter of the oropharyngeal airway increased in the deviation group, while it decreased in the normal group. The postoperative reductions in cross-sectional area, volumes, and total volume of the oropharynx and hypopharynx were more pronounced in the normal group.

Conclusion: In patients with skeletal Class III high-angle malocclusion, mandibular deviation results in narrowing of the lower portion of the upper airway. The orthognathic surgical correction of mandibular deviation compensates to some extent for the reduction in the cross-sectional area and volume of the upper airway caused by the surgery itself.

Clinical relevance: For patients with skeletal Class III high-angle malocclusion with mandibular deviation, a thorough assessment of the upper airway should precede the selection of orthognathic surgery procedures. For patients with normal preoperative upper airway morphology, consideration may prioritize correction of facial aesthetics and occlusion. For patients with pre-existing narrow upper airways, as mandibular setback exacerbates narrowing and the compensatory effect of mandibular deviation correction on the airway is limited, it is suggested that these patients prioritize bimaxillary surgery or reduce the amount of mandibular setback to better promote postoperative respiratory function health.