Fractures Involving the Orbit

Abstract

Orbital and periorbital injury can occur with localized trauma to the eye or in the setting of multiple trauma associated with injury to other vital organs. A reported 16% of major trauma patients have ocular or orbital injury, and 55% of patients with facial injury have associated ocular or orbital injury. In general, the amount of ocular, soft tissue, and bony damage is related to the amount, duration, and direction of force applied to the orbit and face. Nevertheless, orbital injury is common and can be a subtle finding in the context of other facial or life-threatening injuries. Geometrically, the bony orbit most closely resembles a four-sided pyramid consisting of an apex, a base, and four sides: roof, floor, medial wall, and lateral wall. The absence of the orbital floor posteriorly and the inclination of the lateral wall toward the medial wall changes the geometric shape from a four-sided pyramid to a three-sided pyramid at the orbital apex. The bony margin circumscribes the orbital entrance and provides anterior support for the thin bones of the interior walls of the orbit. Rounding of the orbital walls blends demarcation of the superior, medial, inferior, and lateral walls. The entrance measures 40 mm horizontally and 32 mm vertically. The widest portion of the orbital margin lies about 1 cm behind the anterior orbital rim. In adults, the depth from orbital rim to apex varies from 40 to 45 mm. Safe subperiosteal dissection may be accomplished along the lateral wall and orbital floor for 22 mm and along the medial wall and orbital roof for 30 mm. The volume of the orbit is approximately 30 cc. The triangular floor of the orbit serves as the roof of the maxillary sinus. Several areas of thin bone create weak points in the orbital floor that are susceptible to fracture. The thinnest portion is medial to the infraorbital groove and canal, particularly posteriorly, where the medial wall has no bony support. In the posterior aspect of the floor, the infraorbital fissure extends as the infraorbital canal.