Transnasal Approach to the Orbit: The Maxillary Roof

Background and Aim: Transnasal approaches to the orbit have been proposed as minimally invasive surgery alternatives for orbital tumors. The roof of the maxillary sinus is the border between the orbital floor and the nasal cavity. Endoscopic access to the maxillary sinus roof provides visualization of this area and is associated with less morbidity than external approaches. Maxillary sinus roof endoscopy demands the knowledge of endoscopic landmarks. The aim of this presentation is to describe the endoscopic anatomy of the maxillary sinus roof, identify endoscopic anatomical landmarks, and propose a simple anatomical model for the transmaxillary roof approach to the orbital floor.

Material and Methods: One hundred six maxillary sinuses in 53 dry skulls were evaluated using an endoscopic endonasal approach. Cast models of the sinuses were obtained and studied. We endoscopically dissected 34 maxillary sinuses in 17 cadaveric specimens. Using 0-degree and 45-degree rigid endoscopes and an endonasal approach, we provided access to the maxillary sinus roof. Potential bony landmarks were correlated with soft tissue endoscopic anatomy in fresh specimens. The maxillary ostium and maxillary roof were visualized, and their structures were described.

Results: The infraorbital nerve and canal were located in the maxillary roof, and the endoscopic course and relations of the nerve were carefully described. There were large variations in the bone structure of the infraorbital canal. We propose an anatomical model using 3D reconstruction of the maxillary roof cast models. We found that by using an endoscopic approach, the infraorbital canal shape and observations of the cold light source reflections helped to identify the infraorbital nerve and artery.

Conclusions: These results suggest that the infraorbital canal is the most important anatomical landmark for an endoscopic endonasal transmaxillary approach to the orbital floor. Our anatomical model provides the endoscopic anatomy and may be used for the simulation of surgical techniques.