[Endoscopic transorbital approach to the orbital apex and skull base: an applied anatomical study]

Objective: To investigate the anatomical feasibility of the endoscopic transorbital approach (ETOA) to the orbital apex and lateral middle cranial fossa, to identify stable and recognizable surgical landmarks under endoscopic visualization, and to provide morphometric data for preoperative planning and intraoperative navigation. Methods: Stepwise anatomical dissection was performed on five formalin-fixed cadaveric heads and one fresh arterially injected cadaveric specimen to simulate the ETOA using a 0° endoscope. Key structures and their anatomical relationships were observed and recorded. Additionally, high-resolution CT scans of 50 adults were retrospectively analyzed. Three-dimensional reconstructions and measurements were performed using Mimics 17.0 software. Spatial validation was performed using 17 dry skulls to verify the consistency and reliability of osseous anatomical landmarks. Results: Cadaveric dissection identified the meningo-orbital band, superior orbital fissure, optic canal, foramen rotundum, and foramen ovale as reliable surgical landmarks for the ETOA. A topographic map of the surgical region was established based on the endoscopic view. CT measurements revealed the following distances (Mean±SD): the midpoint of the supraorbital rim to the foramen rotundum (57.31±3.59) mm and foramen ovale (71.46±3.42) mm; the lateral orbital rim to the lateral edge of the superior orbital fissure (37.38±2.52) mm; the distance from the superior orbital fissure to the optic canal (9.98±1.49) mm; and the distance from the anterior ethmoidal artery to the optic canal (19.98±2.05) mm. These measurements were consistent with dry skull data, indicating that these osseous landmarks had stable spatial relationships and were suitable for intraoperative localization. Conclusions: The ETOA provides favorable anatomical accessibility and clinical feasibility for lesions involving the orbital apex and lateral skull base. Key osseous structures demonstrate high identifiability and stable spatial relationships, serving as critical references for intraoperative navigation and preoperative pathway planning. The quantitative anatomical framework established in this study provides critical morphometric support for minimally invasive surgery targeting lesions in this region.