A cadaveric study investigating the anatomy of the medial orbital wall

Abstract

The purpose of this study is to investigate the applicability of the current surgical guideline, known as '24-12-6' surgical guideline, in the Hispanic and European populations. This guideline is used during numerous orbital surgeries and states that the distance between the anterior lacrimal crest (ALC) to the anterior ethmoidal foramen (AEF) (24 mm), the AEF to the posterior ethmoidal foramen (PEF) (12 mm), and the PEF to the optic canal (OC) (6 mm) follows a Rule of Halves. Previous studies suggest this surgical guideline is not applicable for all ethnicities; however, to our knowledge, no data has been published regarding the accuracy of this guideline pertaining to the Hispanic population. An experimental study was performed on 79 orbits (52 cadavers) donated to the Human Anatomy Program at UT Health San Antonio. The ALC, AEF, posterior ethmoidal foramen, and OC were identified; the orbit was enucleated and all remaining soft tissue removed. The distance between each landmark was recorded using a digital caliper. For all cadavers studied, the distances between the ALC, AEF, posterior ethmoidal foramen, and OC were 24.76 mm, 13.89 mm, and 7.61 mm, respectively. Thus, the '24-12-6' surgical guideline was not applicable to the sample studied. Based on ethnicity data, these relationships were also not true for the European or the Hispanic populations. Therefore, significant anatomical variations exist in the current surgical guideline. Clinicians may need to adjust their methodology during surgical procedures in order to optimize patient care.

Endoscopic-assisted Orbitotomy for Obliteration of Orbital Arteriovenous Fistula Refractory to Endovascular Techniques

“…Because the preoperative digital subtraction angiography in the present case showed the AVF was fed by the posterior ethmoidal artery, the shunt was expected to be found in the vicinity of the posterior ethmoidal foramen, that is, approximately 36 mm behind the anterior lacrimal crest. 17 Cauterization of a lesion so close to the orbital apex, almost 6-7 mm from the optic canal, entails a significant risk of optic neuropathy. A propensity for bleeding from the AVF would further complicate the procedure both in terms of safety and feasibility of accurate target ablation.…”

Anatomy of lacrimal sac fossa affecting success rate in endoscopic and external dacryocystorhinostomy surgery in Mongolians

“…The anatomical relationship that describes the distance between the anterior lacrimal crest to the anterior ethmoidal foramen (AEF), the AEF to the posterior ethmoidal foramen (PEF), and the PEF to the optic canal, is known as the ‘24-12-6’ orbital surgical guideline or the “Rule of Halves” in western textbooks. Recent studies illustrate, there is significant variability in the medial orbital wall measurements between different populations and against the surgical guideline [ 18 ]. Our study result support this idea on the surgical anatomical difference of lacrimal sac fossa is existing in Mongolians.…”

Practical Considerations in Computerized Surgical Planning for Frontofacial Surgery

“…19 The inferior orbital fissure has a more superficial lateral branch containing noncritical structures including the zygomaticofacial nerve and inferior ophthalmic vein; the medial branch of the inferior orbital fissure is covered with a thin layer of bone and contains the more critical infraorbital nerve and artery. 20 Medially, the orbital wall houses the lacrimal fossa and surrounding attachments of the medial canthal tendon ( Fig. 1B ).…”

“…The anterior ethmoidal artery and foramen are 24 mm behind the anterior lacrimal crest, and easily visible from a bicoronal approach. 20 Medial wall osteotomies may safely be placed just anterior to the anterior ethmoid artery.…”