[Endoscopic Anatomy of the Inferior Orbital Fissure-Müller’s Muscle Structural Unit at the Medial Sellar Orbital Junction and its surgical relevance]

Background: Diseases of the orbit represent a surgical challenge, particularly those compromising the orbital apex. Optimal surgical access should provide the best possible exposure, allowing to identify certain key anatomical structures, called landmarks.

Objective: Describe the endoscopic anatomy of the structural unit formed by the Inferior Orbital Fissure (IOF) and the Müller’s muscle (MM) at the orbital apex (OA), thus generating a new endoscopic anatomical landmark.

Materials and methods: A bone-descriptive analysis of the IOF in dry craniums, was followed by dissection and endoscopic study of six heads (twelve sides), colored and fixed in formaldehyde. In ten dry craniums (twenty sides), distances and angles of OA foramina were measured (optic foramen [OF] and foramen rotundum [FR]). Statistical analysis was performed with SPSS 17.0 statistical software (SPSS, Inc. Chicago, IL).

Results: The structural unit IOF-MM was identified in all endoscopic dissections, verifying its intimate relationship with the OA. From the morpho-metric standpoint, OF and FR were found at an average distance of 65.19 mm and 60.16 mm, respectively. The average angle of the OF was 13.32 degrees, whereas the one for FR was 19.31 degrees. We found a significant correlation between OF and FR only on the left side (left hemi-crane) (Kendall Tau b 0.69, p=0.006). There were no anatomical or morphological differences between both sides.

Conclusion: The unit IOF-MM is a constant anatomical landmark, useful and safe under endoscopic technique, which allows the recognition of the OA and its contiguous areas.