Analysis of anatomical variation of the inclination of lamellas attached to the skull base and its correlation with the anterior ethmoidal artery floating in the ethmoid sinus for use in endoscopic sinus surgery.

Attention to the inclination of lamellas attached to the skull base, including the basal lamella of the middle turbinate, facilitates the intraoperative identification of each lamella without requiring the use of a navigation system. We classified the inclination between the lamella and the skull base in preoperative computed tomography (CT) images and examined the relationship between the lamellas attached to the skull base, including the basal lamella of the middle turbinate, and the position of the anterior ethmoidal artery (AEA). We aimed to develop a preoperative classification to help prevent intraoperative injury of the AEA. We retrospectively investigated the paranasal sinus sagittal section CT slices of 366 sides of 183 patients to assess the inclination of lamellas attached to the skull base and the AEA location. We also reviewed the AEA position, its correlation with the supraorbital ethmoid cell, and the lateral lamella of the cribriform plate. We classified the lamella inclination at the skull base as the anterior direction, perpendicular direction, and posterior direction types. Lamellas containing a floating AEA inclined in the anterior direction toward the skull base were observed in 68.9% of sides, inclination in the perpendicular direction was noted in 30.5% of sides, and inclination in the posterior direction was noted in 0.5% of sides. It is easier to identify the AEA intraoperatively when the lamella inclination of the skull base attachment is recognized based on preoperative CT findings. This approach could be applied to all paranasal sinus lamellas and assist in identifying the AEA and other nearby structures.