The role of supraorbital ethmoid cell and the significance of a proposed classification of the anterior ethmoid artery in endoscopic sinus surgery

Abstract

Objective:To investigate the role of the supraorbital ethmoidal cell（SOEC） in identifying the frontal sinus ostium（FO） and the anterior ethmoidal artery（AEA） in endoscopic sinus surgery, and to evaluate the clinical significance of a proposed endoscopic classification of AEA. Methods:The clinical data of 116 patients with chronic rhinosinusitis were collected. Thirty-six patients（47 sides） with SOEC and DraftⅡA frontal sinusotomy were included. The radiological-anatomical relationship between SOECs and FO, AEAs were recorded. Endoscopic classification of AEA was proposed according to the relationship between the AEA and the ethmoidal roof（EF）: type 1, the AEA prominence did not extend beyond the lateral one-third of the EF; type 2, that exceed the lateral one-third but not beyond two-thirds of the EF; type 3, that exceed the lateral two-thirds of the EF. Results:The incidence of SOECs was 26.1%（47/180） of the DraftⅡA operating sides. On computed tomography images, seven sides of FO were occupied by supra agger frontal cells or supra bulla frontal cells; the other 40 sides（85.1%） were immediately anterior to the SOECs. The AEAs were 100% located near the posterior margins of SOECs with 6（12.8%） running under the EF and 41（87.2%） low-lying distant from the EF. Under endoscopy, the identification rate of SOECs was 89.4%（42/47）, and five（10.6%） SOECs were not confirmed due to edematous mucosa, bleeding, and other reasons. The identification rate of the AEA was 76.6%（36/47）, of which type 1, type 2 and type 3 accounted for 41.7%（15/36）, 38.9%（14/36） and 19.4%（7/36） respectively. After removing the frontoethmoidal cells, all the FO were located anteriorly or anteromedially to the SOECs. All the identified AEAs were located in the posterior boundary of the SOEC openings at the level of the anterior ethmoidal foramen. Conclusion:The SOEC is a reliable landmark for locating the FO and the AEA in endoscopic sinus surgery. The new endoscopic classification of AEA helps the surgeon dissect the frontoethmoidal region precisely.