Blow-out fractures of the orbit resultfrom blunt trauma. Blunt objects of small diameter, such as a fist, tennis ball, or baseball, can compress the contents of the orbit so severely that orbital wall fractures. This fracture usually occurs where the bone is thinnest, alongthe paper-thin floor of the orbit over the maxillary sinus. The ring-shaped bonyorbital rim usually remains intact. The fracture can result in protrusion and impingement of orbital fat and the inferior rectus and its sheaths in the frac-ture gap. Where the medial ethmoid wall fractures instead of the orbital floor, emphysema in the eyelids will result.
The more severe the contusion,the more severe the intraocular injuries and resulting visual impairment will be. Impingement of the inferior rectus can result in diplopia, especially in upward gaze. Initially, the diplopia may go unnoticed when the eye is still swollen shut. A large bone defect may result in displacement of larger por-tions of the contents of the orbital cavity. The eye may recede into the orbit (enophthalmos) and the palpebral fissure may narrow. Injury to the infraor-bital nerve, which courses along the floor of the orbit, may result. This can cause hypesthesia of the facial skin.
Crepitus upon palpation during examination of the eyelid swelling is a sign of emphysema due to collapse of the ethmoidal air cells. The crepitus is caused by air entering the orbit from the paranasal sinuses. The patient should refrain from blowing his or her nose for the next four or five days to avoid forcing air or germs into the orbit. Radiographs should be obtained and an ear, nose, and throat specialist consulted to help determine the exact location of the fracture. CT studies are more precise and may be indicatedto evaluate difficult cases.
Tissue displaced into the maxillary sinus will resemble a hanging drop of water in the CT image.
Surgery to restore normal anatomy and the integrity of the orbitshould be performed within ten days. This minimizes the risk of irreversible damage from scarring of the impinged inferior rectus. Where treatment is prompt, the prognosis is good.
Tetanus prophylaxis and treatment with antibiotics are crucial.