Upper airway and sleep quality changes after bimaxillary orthognathic surgery: influence of posterior nasal spine displacement in skeletal class III malocclusion.

Skeletal class III malocclusion often requires bimaxillary orthognathic surgery, but the impact of posterior nasal spine (PNS) displacement on upper airway dimensions and sleep quality remains unclear. This ambispective cohort study evaluated the relationship between three-dimensional PNS displacement and postoperative changes in upper airway dimensions and sleep quality in 33 adults with skeletal class III malocclusion who underwent Le Fort I osteotomy and bilateral sagittal split ramus osteotomy. Cone-beam computed tomography with voxel-based superimposition and level III portable polysomnography (screening tool) were performed preoperatively and postoperatively. Upper airway volumes were segmented into nasopharyngeal, oropharyngeal, and hypopharyngeal regions. Mean PNS displacement was 3.71 ± 1.38 mm anteriorly and 2.12 ± 1.83 mm superiorly. Nasopharyngeal volume decreased significantly from T0 to T1 by a mean of 555 mm3 (∼7% from baseline). Multivariable linear regression further revealed that superior PNS displacement was significantly associated with this reduction (β = -453 mm3/mm, P = 0.001). This reduction did not result in clinically significant deterioration of objective sleep parameters. Pittsburgh Sleep Quality Index scores improved significantly postoperatively (P = 0.040). Oropharyngeal, hypopharyngeal, and total airway volumes showed no significant changes. Superior PNS displacement causes a statistically significant but functionally compensated nasopharyngeal volume reduction, suggesting that controlled posterior maxillary impaction may not adversely affect sleep quality in patients with no significant preoperative obstructive sleep apnea.