Quantitative Analysis and Anatomic Feasibility Assessment of Supraorbital Keyhole Approach: A Review of Cadaveric Studies on Area of Exposure, Angle of Attack, and Surgical Freedom

Background and Objectives: Since its introduction, the standard supraorbital approach (SO) and its modifications—collectively termed supraorbital keyhole approaches (SOKAs) — have evolved to strike a balance between minimal invasiveness, maneuverability, and safety. While clinical and qualitative studies have demonstrated the feasibility of SOKAs, systematic assessment of quantitative anatomic data are lacking. This study reviews cadaveric data on key metrics afforded by SOKAs. Methods: Databases of PubMed, Scopus, and Ovid/Medline were explored in accordance with the PRISMA guidelines to identify cadaveric articles that analyze SOKAs. Quantitative studies assessing surgical exposure (AOE), angle (AOA), and freedom (SF) were included. Results: The review included 22 studies dissecting 127 wet cadaveric heads. Craniotomy dimensions showed a pooled height of 2.25 cm (± 0.62 cm) and length of 2.98 cm (± 0.48 cm). SO provided a total AcoA complex AOE of 114.8 ± 26 to 460.24 ± 160.19 mm 2 , comparable to pterional (PT) and transorbital (TO). Endoscopic visualization added no exposure advantage to routine SO, whereas additional orbital rim osteotomy or using the endoscopic endonasal transtuberculum/transplanum approach (EEATT) afforded wider supra-communicating AOE than SO (29.37 ± 17.27 mm 2 ). For MCA, parasellar region, and posterior circle of Willis, SO afforded AOE of 939 ± 139 to 2080 ± 680 mm 2 , comparable to other SOKAs, mini-pterional (MPT), PT, and orbitozygomatic (OZ) approaches but inferior to TO. SO offered narrower vertical AOAs to the AcoA complex (10.06 ± 4.54° to 20 ± 3.29°) and MCA/parasellar region (12.9° - 30.5°) than OZ and PT, even with orbital rim or sphenoid wing drilling, but comparable to mini-modified OZ in the MCA region. SF for anterior circulation was also smaller for SO (280 ± 280mm 2 ) than MPT, whereas including pterion and sphenoid wing drilling (extended SO) yields comparable results and utilizing a lateral SO for AcoA complex gives superior horizontal AOA (37.58 ± 2.75°) than MPT. The parasellar “volume” of freedom was also smaller in SO (23.60 ± 3.4 to 42.9 ± 15.4 cm 3 ) than in PT. For accessing the anterior cranial base, SO afforded superior SF (4069 ± 136 mm 2 ) in the lateral opticocarotid recess compared with EEATT but was more limited in paramidline and contralateral areas. Conclusion: Morphometric data underline no significant exposure area advantages for SOKAs over traditional craniotomies but highlight their trade-offs between minimal invasiveness and maneuverability. Conventional SO affords limited freedom in the middle fossa, parasellar, and parapeduncular regions but improves with mini-modified OZ, lateral SO, or extended SO. Quantitative cadaveric assessment may not fully replicate real surgery, but it can shape surgical planning and optimization to enhance outcomes. Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany