Computed tomography evaluation of the morphometry and variations of the infraorbital canal relating to endoscopic surgery

Abstract Introduction The course of the infraorbital canal may leave the infraorbital nerve susceptible to injury during reconstructive and endoscopic surgery, particularly when surgically manipulating the roof of the maxillary sinus. Objective We investigated both the morphometry and variations of the infraorbital canal with the aim to show the relationship between them relative to endoscopic approaches. Methods This retrospective study was performed on paranasal multidetector computed tomography images of 200 patients. Results The infraorbital canal corpus types were categorized as Type 1: within the maxillary bony roof (55.3%), Type 2: partially protruding into maxillary sinus (26.7%), Type 3: within the maxillary sinus (9.5%), Type 4: located anatomically at the outer limit of the zygomatic recess of the maxillary bone (8.5%). The internal angulation and the length of the infraorbital canal, the infraorbital foramen entry angles and the distances related to the infraorbital foramen localization were measured and their relationships with the infraorbital canal variations were analyzed. We reported that the internal angulations in both sagittal and axial sections were mostly found in infraorbital canal Type 1 and 4 (69.2%, 64.7%) but, there were commonly no angulation in Type 3 (68.4%) ( p p p  = 0.003). The maxillary sinus septa and the Haller cell were observed in 28% and 16% of the images, respectively. Conclusion Precise knowledge of the infraorbital canal corpus types and relationship with the morphometry allow surgeons to choose an appropriate surgical approach to avoid iatrogenic infraorbital nerve injury.