The infraorbital foramen (IOF) is a paired opening located on the front of the skull within the maxillary bone (upper jawbone). This opening acts as a crucial passageway, allowing communication between the interior of the skull and the soft tissues of the midface. The foramen marks the endpoint of an internal canal that carries bundles of nerves and vessels to the face. Understanding its precise location is important for medical professionals in fields like dentistry, emergency medicine, and plastic surgery.
Anatomy of the Infraorbital Foramen
The infraorbital foramen is located on the anterior surface of the maxilla bone. It sits directly beneath the lower bony rim of the eye socket, known as the inferior orbital margin, and is superior to the canine fossa depression. This placement makes the foramen a key, often palpable, landmark in the facial skeleton.
To locate it accurately, one can use the vertical alignment of the pupil as a guide when the eye is looking straight ahead. The foramen typically lies along the same vertical plane that passes through the middle of the pupil and the second premolar tooth in the upper jaw. Its exact position can vary slightly among individuals.
The foramen is generally found at a distance of about 6 to 10 millimeters vertically below the inferior orbital margin. Studies analyzing skull anatomy report this mean distance to be around 6.5 to 9.2 millimeters below the rim. This small distance highlights the foramen’s proximity to the structures of the eye socket.
The infraorbital foramen is the terminal opening of the infraorbital canal, which transmits the neurovascular bundle forward to the face. Slight variations in the foramen’s location are important for clinicians. The opening can sometimes be found in line with the first premolar or between the first and second premolars, rather than directly over the second.
Structures Exiting the Foramen
The infraorbital foramen provides an exit route for a neurovascular bundle, including a nerve, an artery, and a vein. The most notable structure is the infraorbital nerve, a continuation of the maxillary division (V2) of the trigeminal nerve. The trigeminal nerve is the fifth cranial nerve, responsible for facial sensation.
The infraorbital nerve is purely sensory and immediately divides into several smaller branches upon exiting the foramen. These branches provide sensation to a large area of the midface. They innervate the skin of the lower eyelid, the side of the nose, the anterior cheek, and the upper lip.
Accompanying the nerve through the foramen are the infraorbital artery and the infraorbital vein. The artery, which branches from the maxillary artery, supplies oxygenated blood to the midface structures. The vein collects deoxygenated blood from the same region before draining into larger vessels. The close proximity of these three structures means that any medical intervention or injury affects the entire bundle.
Clinical Relevance of Foramen Location
The precise location of the infraorbital foramen is a frequent target in clinical practice, particularly for regional anesthesia. The infraorbital nerve block is a common procedure used to temporarily numb the area supplied by the nerve. This is achieved by injecting a local anesthetic near the foramen as the nerve exits the bone.
This type of nerve block is widely used in dental procedures involving the upper incisor, canine, and premolar teeth, and surrounding gum tissue. It is also employed during minor surgical procedures on the upper lip, lower eyelid, or nasal area. Accurately identifying the foramen prevents the needle from causing trauma to the neurovascular bundle or nearby orbital contents.
Knowledge of this anatomical spot is also important in managing facial trauma. Since the foramen is located on the maxilla, midface fractures can easily injure the infraorbital nerve bundle. Trauma to this region can result in a loss of sensation (paresthesia or hypoesthesia) in the areas supplied by the nerve. Surgeons must consider the foramen’s location when performing procedures like open reduction of orbital or maxillary fractures to avoid causing permanent nerve damage.