Aerodynamic and anatomical changes of the upper airway after maxillary skeletal expansion in adults

To quantify anatomical and aerodynamic changes of the adult upper airway after maxillary skeletal expansion (MSE) using computational fluid dynamics (CFD) with in vitro validation, and to assess whether expansion magnitude correlates with aerodynamic improvement. Thirty-one skeletally mature adults treated with MSE were retrospectively included. CBCT scans at baseline (T1) and after stabilization (T2) were used to reconstruct and segment airway models into nasal and pharyngeal regions. Steady inspiratory CFD was performed at a bilateral flow rate of 30 L/min and validated in 10 patient-specific 1:1 3D-printed models. Mean expansion magnitude was 4.09 mm. Nasal cavity volume increased (Δ=+3.10 cm³, P < 0.001), whereas pharyngeal MCA showed no significant change ( P = 0.083). Total pressure drop decreased (Δ=−13.95 Pa, P < 0.001), mainly due to a reduction in nasal pressure drop (Δ=−12.81 Pa, P < 0.001); the pharyngeal pressure drop change was not significant ( P = 0.087). Expansion magnitude correlated with nasal pressure-drop reduction ( r = − 0.412, P = 0.021) and nasal volume increase ( r = 0.470, P = 0.008), but not with total pressure-drop reduction ( P = 0.074). MSE yields region-specific aerodynamic improvement predominantly in the nasal airway, with limited pharyngeal aerodynamic change. Aerodynamic improvements after MSE should not be assumed to extend uniformly to the pharyngeal airway; patients with marked pharyngeal narrowing may require individualized airway evaluation and adjunctive management beyond expansion alone.