Computational Fluid Dynamics Simulation Of Upper Airway Changes In Skeletal Class ? Patients Using Surgery-first Approach

Background and Objectives:To investigate postoperative airway morphological changes for the correction of skeletal class ? dentofacial deformities using surgery-first approach.The computational fluid dynamics with Large Eddy Simulation was also conducted to evaluate long-term upper airway flow field changes after the treatment.Materials and Methods:Eight subjects[females,(27.9±10.2)years old]underwent bimaxillary surgery using surgery-first approach were selected.All patients underwent double-jaw surgery,including maxillary Le Fort I osteotomy,sagittal split ramus osteotomy and genioplasty.CBCT data taken by the patient before operation(T0),1 year(T1)and 2 years(T2)were import into Mimics 19.0 software for three-dimensional measurement,xflow2017 software was used for numerical simulation of the flow field.All the results were analyzed by paired sample t test using SPSS21.0 software.p ?0.05 indicated that the difference had a significant statistical difference.Results:1.The mean postsurgical PNS movement was 3.30±1.63mm forward,3.04±1.19mm upward,respectively.B point movement was 6.78±2.17mm backward,and the maxillary clockwise rotation angle was 3.67 °±2.35°.The volume of retroglossal oropharynx and hypopharynx decreased by 1783.30±1653.34mm3 and 1285.90±1479.23mm3,respectively.The cross-sectional area at the uvula tip decreased by 61.76±71.61mm2,and the sagittal diameter decreased by 3.47±1.92mm.The cross-sectional area at the top of the epiglottis decreased by 85.39±76.76mm2,and the transverse and sagittal diameters decreased by 2.13±2.24mm and 3.08±2.63mm,respectively.The soft palate length increased by 4.16±2.35mm,and the thickness decreased by 1.24±0.50mm.All the results showed significant differences(p?0.05).No significant result was found in 2-year analyses,neither in postsurgical upper airway changes nor surrounding tissues.2.Computational fluid dynamics simulation showed that 1 year after the surgery,the maximum velocity of retroglossal oropharynx increased by 1.85±0.63m/s,the pressure drop increased by 8.86±3.94Pa significantly.(p<0.05)The maximum velocity of hypopharynx increased by 4.36±1.19m/s,the pressure drop increased by 26.48±18.61 Pa significantly.(p?0.05)However,the maximum flow velocity and pressure drop of retroglossal oropharynx and hypopharynx decreased 2 years after the treatment,and there was no significant difference compared with preoperative situation(p?0.05).Conclusion:1 year after surgery-first approach in skeletal class ? patients,morphological narrowing and increased airflow resistance were found in retroglossal oropharynx and hypopharynx structures.But all the changes did not persist in 2-year's postsurgical analysis.There was no significant effect on nasopharynx and retropalatal oropharynx.