Orbital Bony Anatomy and Orbital Fractures

The bony orbit is pyramidal-shaped, with an average volume of approximately 30mL. It is composed of seven bones: frontal, sphenoid, ethmoid, lacrimal, maxillary, palatine (variable), and zygomatic. The medial walls are parallel, but the lateral walls are at a 45° angle. There are three major foramina in the orbit: the optic canal, the superior orbital fissure, and the inferior orbital fissure. It is through these, and other minor foramina, that important structures enter and exit the orbit. Orbital fractures are common when a blunt force is applied to the orbital rim, including fractures of the floor, medial wall, and the zygomatic-maxillary complex. Repair of these fractures is critical to prevent entrapment or further injury to the soft tissues within the orbit.