Location and Structure
The canal runs through the substance of the maxillary body (corpus maxillae).
It begins on the orbital surface (facies orbitalis), which forms the floor of the orbit. Here, the infraorbital groove (sulcus infraorbitalis) continues forward into the infraorbital canal.
The exit of the canal is located on the anterior surface of the maxilla (facies anterior) and is called the infraorbital foramen (foramen infraorbitale). It lies inferior to the infraorbital margin (margo infraorbitalis) and opens into a depression known as the canine fossa (fossa canina).
The axis of the anterior segment of the canal is directed forward, medially, and downward. The axes of the right and left canals intersect slightly above the incisive papilla between the maxillary central incisors.
Contents of the Infraorbital Canal
The canal contains the infraorbital neurovascular bundle, which emerges into the loose connective tissue of the canine fossa:
- Infraorbital nerve (n. infraorbitalis) — the terminal branch of the maxillary nerve (CN V2). It gives off the anterior and middle superior alveolar branches. After exiting the foramen, the nerve divides into a "pes anserinus minor" (lesser goose's foot). The area of sensory innervation includes the skin of the infraorbital region, upper lip, lateral surface of the nose, and lower eyelid.
- Infraorbital artery (a. infraorbitalis) — a branch of the third (pterygopalatine) part of the maxillary artery. Inside the canal, it gives off the anterior superior alveolar arteries (aa. alveolares superiores anteriores).
- Infraorbital vein — drains into the inferior ophthalmic vein or the pterygoid venous plexus.
Topography and Anatomical Connections
Through the infraorbital canal, the orbit communicates with the facial region, the maxillary sinus, and the dental alveoli of the incisors and canines.
The connective tissue of the infraorbital region communicates with the orbital fat through the infraorbital canal.
Clinical Significance
- Infraorbital nerve block: Used to anesthetize the incisors, canine, premolars, and partially the mesial buccal root of the first molar, as well as the adjacent vestibular bone and soft tissues. In the extraoral approach, the needle is directed posteriorly, laterally, and superiorly—opposite to the axis of the canal. Modern techniques involve depositing the local anesthetic solution near the entrance of the infraorbital canal without entering the canal itself, reducing tissue trauma. Potential complications include vascular injury, hematoma, skin ischemia, diplopia, and infraorbital neuritis.
- Pathway of infection spread: The subcutaneous tissue of the infraorbital region communicates with the orbit via the infraorbital canal. Odontogenic infections can originate from the maxillary incisors, canines, and premolars. Thrombophlebitis of the facial angular vein can spread to the ophthalmic veins, which directly connect to the dural venous sinuses. This poses a risk of cavernous sinus thrombosis, meningitis, and meningoencephalitis.
- Trigeminal neuralgia: Congenital or acquired narrowing of the infraorbital canal or foramen is a contributing factor in peripheral trigeminal neuralgia.