Blowout fractures are the most common orbital fractures. These injuries occur when a blunt object strikes the globe, resulting in expansion of orbital contents and subsequent rupture through the bony floor. A direct blow to the orbital rim will also result in a blowout. Four clinical findings suggest the diagnosis. (1) Rare patients may have enophthalmos, or sunken globe, when a large section is ruptured. (2) Infraorbital anesthesia is a more common finding and develops when the infraorbital nerve is contused by the initial trauma or when compressed by bony fragments. Anesthesia of the maxillary teeth and upper lip is more reliable than numbness over the cheek. (3) Diplopia, particularly on upward gaze that usually indicates inferior rectus muscle entrapment, is another important clinical finding. However, the etiology of diplopia may be multifactorial and does not necessarily imply entrapment of extraocular muscles. True entrapment occurs in only a small minority of patients with diplopia, and etiologies that are more common include direct muscle injury, damage to the third nerve, or entrapment of periorbital fat. Mechanical entrapment is readily diagnosed by the forced duction test. To perform this test, apply a few drops of ophthalmic anesthetic in the conjunctival sac, grasp the inferior sclera with a toothed forceps, and gently tug upward. In true entrapment, the eye remains fixed. It is not imperative that an emergency physician perform this test, because CT scanning and consultation are necessary for patients with posttraumatic diplopia. (4) Occasionally, a step-off deformity can be palpated over the intraorbital rim. Subcutaneous emphysema is pathognomonic for fracture into a sinus or nasal antrum.
Plain films are useful in the diagnosis of blowout fractures. The "hanging teardrop" sign is seen with herniation of orbital fat into the maxillary sinus, whereas the "open bomb-bay door" results from bone fragments that protrude into the sinus. Air/fluid levels in the maxillary sinus are frequently seen in association with these signs. At least one author suggests that only patients with well-defined indications for surgery (enophthalmos of more than 2 mm and/or persistent diplopia) require any imaging studies at all.16 This is perhaps a minority view.
Once a blowout fracture is confirmed either radiographically or clinically (i.e., diplopia or subcutaneous air), obtain a CT scan with coronal sections to determine the surface area of the broken floor. This film could be done as an outpatient study, but it may be expedient to obtain it during the ED stay. Patients with orbital fractures tend to have low compliance with follow-up.17 Some centers have used ultrasound to evaluate orbital floor fractures, but this is not as sensitive as CT.
There is significant controversy as to timing and necessity of orbital floor repair. Some specialists use CT to determine the need for surgery, whereas others repair the orbit only if there is enophthalmos or persistent diplopia. Although enophthalmos mandates surgical repair, most diplopia (up to 70 percent) resolves spontaneously within several months.
Many consultants recommend antibiotics active against sinus pathogens for patients with subcutaneous emphysema. Patients with fractures into the sinus should avoid blowing their nose to prevent accumulation of subcutaneous air.
In rare circumstances, malignant periorbital emphysema may jeopardize vision by injuring the retina or optic nerve. In such cases, emergency cantholysis may salvage the patient's vision. In patients with massive emphysema, and no evidence of an open globe, measure the intraocular pressure. If the pressure is significantly elevated, immediately consult an ophthalmologist and discuss the need for an emergency cantholysis.
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