Orbital Fractures

Background

Orbital fractures are among the most common facial fractures, and their associated cost to the healthcare system has been on the rise. Surgical repair of orbital fractures has been shown to add a day of hospitalization and an average of $22,000 in hospital charges for the average trauma patient. Treatment of orbital trauma at high-volume specialized eye centers has been shown to reduce cost compared to management at other hospitals. The incidence and etiology of orbital fractures vary greatly with geography, demographics, and socioeconomic factors, such as rates of violence and access to automobile safety technology. Among the civilian population within the United States, 38% of orbital fractures result from motor vehicle collisions, followed closely by 34% from assault; falls and sport injuries account for another 15% and 7%, respectively. Sixty-eight percent of orbital fracture patients are male and over half are aged between 18 and 44. Approximately 1 in 4 orbital fractures in the United States are managed surgically.

Surgical Anatomy

A thorough understanding of orbital anatomy is key to achieving optimal clinical outcomes and minimizing postoperative complications. The bony orbit is approximately 30 mL in volume and 35–40 mm in length. The orbital floor is composed of the maxillary, zygomatic, and palatine bones. The thin medial wall includes the orbital plate of the ethmoid bone, lacrimal bone, frontal process of the maxillary bone, and the lesser wing of the sphenoid ( Fig. 1.9.1 ). The posterior maxillary wall is frequently used as a bony landmark for the orbital apex, beyond which dissection should be avoided to minimize the risk of injury to the optic nerve.

The orbit includes six muscles responsible for extraocular movements. The four rectus muscles originate at the posterior orbit at a fibrous ring called the annulus of Zinn. The inferior rectus runs along the orbital floor and attaches approximately 6.5 mm inferior to the limbus. It must be evaluated for entrapment or rounding on computed tomography (CT) following orbital trauma. The inferior oblique muscle has its origin at the maxillary bone, just lateral to the opening of the nasolacrimal duct, and inserts on the lateral aspect of the globe. Its origin may come in the way of surgical access, particularly during combined floor and medial wall fracture repair. The anterior and posterior ethmoidal arteries run along the frontoethmoidal suture line at the superior border of the medial orbital wall, and must likewise be protected during dissection. The anterior ethmoidal artery lies approximately 24 mm from the lacrimal crest; the posterior ethmoidal artery may be found 36 mm from the lacrimal crest and approximately 6 mm from the orbital apex.

Clinical Presentation

As with any injury, a detailed patient history should be taken upon presentation following orbital trauma. Evidence of head or neck injury, loss of consciousness, nausea, and vomiting are all particularly relevant in facial trauma patients. Muscle entrapment or increased orbital pressure may trigger the oculocardiac reflex, leading to syncope, nausea, vomiting, or even life-threatening arrhythmias. The clinical history should include perception of a clear understanding of the mechanism of injury; a direct blow to the orbit or high-energy trauma should raise the suspicion for globe injury or other associated injuries. In fact, the mechanism of injury has been found to be a better predictor of visual prognosis than the specific pattern of facial fractures. The age, baseline vision acuity and occupational history will likewise factor into the surgical management of an orbital fracture. Although focus is generally placed on preserving primary and downward gaze, patients should be asked about any activities that require prolonged upward gaze or extensive extraocular movement. A young heavy machinery operator, baseball outfielder, or pilot may warrant more aggressive surgical intervention to minimize the risk of posttraumatic diplopia.

The initial physical examination of any trauma patient should focus on ensuring adequate ventilation, hemodynamic stability, and prompt assessment of any life-threatening injuries. Once stable, every patient should undergo at least a basic eye exam, pending more thorough ophthalmologic evaluation. An initial eye exam in the emergency room should at the least include visual acuity testing, extraocular movements, pupillary exam, and an external exam. Evidence of diminished visual acuity, proptosis, or afferent pupillary defect all raise the suspicion for orbital compartment syndrome, which should prompt an emergent cantholysis to decompress the orbit. Bradycardia and defects in extraocular motility should raise concern for muscle entrapment. True muscle entrapment is rare in the adult population owing to diminished orbital wall bone elasticity, and significant periorbital edema may sometimes limit extraocular movements. Forced duction testing may be performed at the bedside to rule out entrapment. The external exam should assess any point tenderness, bony step-offs, crepitus, and sensory deficits; trauma to the infraorbital nerve may frequently lead to dysesthesia. Globe position should be assessed for inferior displacement, enophthalmos, or exophthalmos. A flat anterior chamber, misshapen pupil, or circumferential subconjunctival hemorrhage should raise the suspicion for globe injury. Lateral or medial canthal deformity may indicate either zygomatic involvement or a naso-orbital ethmoid fracture, respectively.

Full ophthalmological evaluation and clearance is critical for all orbital fracture patients prior to surgical repair. In addition to the aforementioned basic eye exam, ophthalmological evaluation should include a more thorough assessment of visual acuity, globe pressure, visual fields, a slit lamp ocular exam, and a retinal exam. Approximately 22%–29% of orbital fracture patients will present with concomitant ocular injuries. In one series, 79% of open globe injuries resulted in blindness. Several studies have demonstrated higher incidence of globe injuries associated with blow-out fractures compared to fractures with rim involvement.

Any evidence of muscle entrapment on exam should warrant early surgical intervention within 24–48 hours. Several studies have demonstrated increased risk of late diplopia with delayed repair in the setting of muscle entrapment. It has been postulated that true muscle incarceration leads to occlusion of the artery running in the central portion of the inferior rectus muscle, resulting in scarring and fibrosis within the muscle. Persistent bradycardia and hemodynamic instability secondary to the oculocardiac reflex are additional indications for immediate surgical repair. Additionally, many authors advocate immediate repair of large wall defects that result in early enophthalmos on presentation.

The timing of surgical repair of orbital fractures in the setting of concomitant globe injury remains controversial. On one hand, early intervention risks further trauma to a ruptured globe, compromising long-term vision outcomes. On the other hand, delaying repair of facial fractures may be detrimental to long-term cosmetic outcomes. Within the reconstructive surgery literature, many authors support careful early repair of orbital fractures with associated globe injury, particularly in the setting of high-energy penetrating trauma, where return of visual acuity is unlikely.

In the absence of globe injury or indications for immediate repair, many authors advocate repair of orbital fractures within a 2-week window. The degree of scarring and adhesions tend to increase after 2 weeks, complicating and decreasing the effectiveness of surgical repair because of fixed scar tissue. Conversely, waiting several days following initial injury may help with resolution of periorbital edema, which might otherwise complicate access during repair. Some feel that the immediate post-injury period is more vulnerable to spasm in the circulation to the optic nerve.