The Study On The Upper Airway Morphology And Flow Dynamics Of Patients With Micrognathia Received Mandibular Advancement

Unilateral or bilateral reduced mandibular size or retrognathia are the performances of micrognathia. Micrognathia not only affects patients’ appearances,but also leads to occlusal disorder.It is potentially lethal for it is often accompanied with severe obstructive sleep apnea hypopnea syndrome(OSAHS). Orthognathic surgery or distraction osteogenesis is an effective method for the treatment of micrognathia with OSAHS.O n the evaluation of the operation’s effect, the current literature focus on craniofacial and upper airway’s morphology change.The change of air flow dynamics in upper airway is still unclear.Therefore,this study established 3D models of patients with micrognathia before and after surgery. We used computational fluid dynamics method to numerical simulation、calculation and analyzed the upper airway flow dynamics.The study aimed to explore the mechanism of operation and we wondered whether facial morphology might correlate with upper airway function.Objective:The study was to analyze the change of the morphology and the internal flow of the upper airway after surgery by computational fluid dynamics(CFD).Method:Five patients with micrognathia who met the inclusion criteria,three female,two male,aged 32-49,accepted CT scan before and six months after the surgery. After converting CT scan into Dicom file format,we were able to use Mimics to construct three-dimensional models of upper airway.In the use of ANSYS software,the models were generated into mesh files and calculated.With the aid of Tecplot and ANSYS,we made the results into visual image and obtained relative information.The data was compared by paired t-test or Wilcoxon signed-rank test analysis.Statistical software SPSS(version 16.0;SPSS Inc,USA).Results:1、 We constructed fluid dynamics model of upper airway before and after the surgery;2、 Each region’s volume of the upper airway of the patients increa sed(P<0.05),while the palatopharyngeal section(increased by 98%) and glossopharyngeal section(increased by53%) were the major change regions. The lower bound of palatal pharynx(the third cross section),which increased by251%(P<0.05),was the most narrow area of upper airway. The increase in the nasopharyngeal area after the surgery had no significant difference(P>0.05);3、 The average flow rate at palate pharynx was apparently decreased after the surgery,from7.8394m/s to 3.8598m/s(P<0.05).While the tongue pharynx region’s average flow rate decreased from 6.5119m/s to 4.0849m/s(P<0.05);4、 The airflow resistance of the pharyngeal reduced by 63.49% after the surgery(P<0.05),from 315Pas/L to 115Pas/L.Conclusion:Patients with micrognathia who received mandibular advancement may correct occlusal deformity,expanse the upper respiratory tract,decrease the negative pressure and maintain the patency of the airflow.