Anatomical Study of the Intraosseous Pathway of the Infraorbital Nerve.

Background: The infraorbital nerve (ION) is at risk for iatrogenic injury during orbital floor repair. The authors aim to anatomically characterize the intraosseous course of the ION between the inferior orbital fissure and infraorbital foramen.
Methods: Ten cadaver heads (20 orbits) were dissected, with exposure of the orbital floor. The ION was identified from the infraorbital fissure to inferior orbital foramen. The presence and caliber of an osseous roof was noted. Distances measured were infraorbital foramen to infraorbital margin; length of the inferior orbital groove; length of the inferior orbital canal; length from the inferior orbital fissure to the infraorbital margin.
Results: Three variations of the osseous anatomy around the ION were identified. Four cadavers had no identifiable groove (Type 1, 40%) and the ION was completely roofed throughout its course. Five specimens exhibited a thin, transparent osseous roof over the nerve before forming the true canal, which we describe as a "pseudocanal" (Type 2, 50%). A true groove was seen in both orbits from a single cadaver (Type 3, 10%). Each cadaver had an ION course of the same type on both sides. Mean ± SD intraorbital foramen to infraorbital margin distance was 7.1 ± 1.4 mm. Distance from the infraorbital fissure to the infraorbital margin was 28.5 ± 2.3 mm.
Conclusions: The course of the infraorbital nerve can be described as Type 1 (true canal), Type 2 (pseudocanal), and Type 3 (groove and canal). The authors propose that this novel classification system will raise awareness of variations in orbital floor anatomy.