Computational fluid dynamic study of the pharyngeal airway characteristics before and after mandibular setback surgery in patients with mandibular prognathism

Mandibular prognathism had been one of the most inconvenienced deformities developed in humans. This type of deformity possesses a protruded mandible jaw, and it can cause inconvenience in talking chewing and affect the aesthetic of the person diagnosed with this problem. However, this problem can be solved through mandibular setback surgery. This surgery will reposition the mandible jaw backward. The main concern of this surgery is, by repositioning the mandible jaw backward, the cross-sectional area of the airway will also be reduced. This condition might induce the iatrogenic of Obstructive Sleep Apnea (OSA). Thus, this study analyzed the characteristic of the pharyngeal airway in pre-treatment and post-virtual-operative conditions. This analysis simulates the pharyngeal airway with the Computational Fluid Dynamic (CFD) method. The respondent's data was obtained from computed tomography (CT) scan and was modeled into a 3-dimensional (3D) model. The simulation process takes place using the 3D model, mesh generation, and boundary conditions set-up. The flow pattern, pressure drop, airway wall shear stress, and turbulent kinetic energy were compared between both simulations. The simulations result present that, after the surgery, the pharyngeal airway decreases significantly. The pressure drop, flow pattern, airway wall shear stress (WSS), and turbulent kinetic energy (TKE) seem more significant around the critical plane in the post-treatment condition. However, these factors did not contribute to the OSA as it is not large enough to become the cause of OSA.