Comparison of airflow characteristics after Draf Ⅲ frontal sinus surgery and normal person by numerical simulation

Draf III frontal sinus surgery is confirmed as an effective surgical treatment for refractory sinusitis and frontal sinus tumors, etc. Although it has been reported to improve symptoms and reduce the recurrence rate of polyps significantly, the study of airflow characteristics in frontal sinus after Draf III is still rare, especially compared with normal person. This study was designed to describe the airflow characteristics of frontal sinus after Draf III procedure and differences compared with normal subject. One patient with refractory sinusitis received Draf III procedure15 months ago, and one normal person were selected retrospectively. The two subjects reported no discomfort and no abnormalities in their paranasal sinus within computed tomography scans. Computational fluid dynamics and numerical simulation calculation was performed with the finite volume method. The quantitative indexes of airflow in the frontal sinus of Draf III and normal subjects were achieved. Areas of relatively high-pressure and high wall shear stress located in a posterior part of frontal sinus ostium in both models. Inside frontal sinus, pressure and velocity of flow between Draf III and normal models were statistically significant differences (p < 0.01) after analyzed by Mann-Whitney U test. But airflow pattern of each section in frontal sinus was basically the same. Draf III sinus surgery is able to achieve nasal airflow patterns similar to those of normal person. Although values of airflow pressure and velocity were different from normal person, patients could have no subjective discomfort after surgery. "Frontal T" structure is a key anatomical site interacted with airflow to be an important cause of postoperative edema after Draf III procedure.