This article is from November/December 2007 and may contain outdated material.
A baseball traveling 55 mph will rupture the globe of a human cadaver precisely three microseconds after impact.1 The energy required for a metal rod to fracture a cadaver orbital floor is 78 millijoules.2
Laboratory calculations like those—often polished down to newtons-per-millisecond—probably hold no consolation for Juan Encarnacion, the St. Louis Cardinals outfielder who suffered severe ocular trauma from a wild foul ball in August. Amazingly, Mr. Encarnacion’s globe was not ruptured, but the Associated Press said his physician described the orbital fractures as “the worst trauma I’ve seen.”
A blow like that initially causes extensive edema, said Col. Robert A. Mazzoli, MD, but when the swelling subsides it’s important to promptly plan a repair strategy. “Once the body is injured, it starts healing immediately. The longer surgery is delayed, the longer the body is healing and displaced soft tissues are getting knitted into the bone. If tissues are incarcerated or strangulated, the lack of circulation is likely to cause long-term impairment of function.” Dr. Mazzoli is the consultant in ophthalmology to the Surgeon General of the Army, as well as chief of ophthalmology and director of ophthalmic plastic, reconstructive and orbital surgery at Madigan Army Medical Center in Tacoma.
The Poor, Fragile Floor
Orbital fractures are a common presentation to ophthalmologists who treat blunt trauma, and fractures of the floor are the most common of all. The fragility of the orbital floor is eloquently considered in a chapter from Ophthalmic Care of the Combat Casualty, coauthored by Dr. Mazzoli. “The orbital floor and medial wall, being adjacent to sinus air spaces, are especially vulnerable to hydrostatic and mechanical buckling forces. Although the bone of the medial wall (the lamina papyracea) is physically thinner than that of the orbital floor, the honeycombed arrangement of the underlying ethmoid air cells gives the medial wall a significant structural advantage over the floor, which is obliged to sit over the cavernously empty maxillary sinus.”3
A break without a rupture? The orbital floor, in fact, may actually be more likely to fail before the globe ruptures. “One of the things we see with orbital floor fractures, what we call a blowout fracture, is that the eyeball itself is often the conduit of force,” said Jon M. Braverman, MD, associate clinical professor of ophthalmology at the University of Colorado in Denver. “As the globe is deformed in its anterior/ posterior diameter, it expands in its equatorial diameter. This elastic force redirection compresses orbital soft tissue, which then jackhammers the orbital floor and blows the bone out into the sinus.” Dr. Braverman works with eye residents at Denver Health Medical Center, and has a special interest in the thresholds of pressure that determine globe ruptures and orbital fractures. The fact that impacts such as the one suffered by Mr. Encarnacion do not always rupture the globe may suggest that a sophisticated anatomic principle is at work. (See “Hail the Heroic Floor.”)
Big bang, brittle orbit. A direct blow to the globe, generating retropulsion and compression of intraocular contents, is considered the “orbital hydrostatic” model of floor fractures, whereas a blow to the rim or zygoma, leading to bone-to-bone transmission of energy, is the “mechanical buckling” model.
Whether orbital fractures are hydrostatic or buckling in nature, the sorts of impacts that cause them are well-known, according to Philip L. Custer, MD, professor of ophthalmology and visual science at Washington University in St. Louis. “The traditional mechanism that we all learn in residency is that an object big enough to stop at the orbital opening yet small enough to protrude into and compress the orbital contents, such as a tennis ball, baseball or fist, abruptly increases the pressure within the orbit. Something’s got to give, and the weakest points are the floor and medial wall. But we also now know that similar fractures are caused by impacts to the malar eminence. This is very common in the elderly: They miss a step, fall and strike their cheek on a piece of furniture or the sidewalk curb.”
Old and young at risk. Ferenc P. Kuhn, MD, PhD, associate clinical professor of ophthalmology at the University of Alabama in Birmingham, agreed. “Falls constitute a significant category of eye trauma among the elderly, since it’s so easy to crash against a blunt object during a fall.” Dr. Kuhn, who is also a professor of ophthalmology at the University of Pecs in Hungary, said that eye trauma in the elderly appears to be increasing, thanks to a development that informs virtually all of modern life: people are living longer. “The number of elderly has increased, and, moreover, the percentage of injuries is higher in the elderly than in younger people.”
But the elderly do share the demographic burden of eye trauma with young men, according to Dr. Braverman. “We see a lot of ‘weekend warriors’ in the ER, guys who were playing sports or partying a little too hard.” Dr. Custer added that he sees plenty of floor fractures from fistfights and motor vehicle accidents. “And many of these will have diffuse facial fractures on top of orbital fractures.”
Finding the Fracture
Evidence of an orbital fracture may be obvious or elusive. “First of all, we need to look for suggestive signs: double vision, or numbness of the cheek and the upper lip and teeth on one side,” said Dr. Custer. “The V2 nerve that goes to those structures, the infraorbital nerve, passes through the floor. If the floor is broken, that nerve can be traumatized and you get numbness in the distribution of that nerve. We also look for orbital emphysema; the patient may have blown their nose, and air is pushed through the fracture and into the surrounding subcutaneous tissue.”
Dr. Custer said that computed tomography is the imaging of choice to verify an orbital fracture. “If we really suspect a fracture we need to order a CT with both axial and direct coronal views. Those are going to be the best studies.”
Trapdoor fractures. An eye that exhibits limited range of motion, said Dr. Mazzoli, suggests that intraorbital contents are entrapped by broken bone. “Interestingly, the larger fractures are actually less likely to entrap tissues. In small fractures a hinged plate often drops down, allowing the soft tissues to herniate; then the plate hinges back up and incarcerates those tissues, which tethers the eye. Those patients may report eye ache with upward gaze, or you’ll notice them guarding their gaze, avoiding certain directions.”
Greenstick trapdoors. In young people in particular, Dr. Mazzoli said, the bones aren’t quite as brittle as in older people, and so are less likely to produce a clean break. “More elastic bones are more likely to incur soft ‘greenstick’ fractures, which, in turn, make them more likely to break incompletely, and entrap periorbital tissue.”
Beyond the black eye. If the injury has pulverized the floor, however, then there are no large plates left to entrap anything. And, in fact, if Dr. Mazzoli has a patient who still has full range of motion after a strong blow to the eye or face, that alone makes him suspicious of a large floor fracture. “A not uncommon situation is when a young guy comes into the ER having gotten an elbow or softball to the eye. He’s got a black eye but full range of motion. He might just have a black eye, or he might have a huge floor fracture. If you don’t treat that, you’re going to end up with enophthalmos or hypoglobus. You may not see it right away because swelling is keeping the eye in place, so you look for associated symptoms of fractures: double vision, malocclusion, trismus or numbness in the cheek or teeth.”
White-eyed blowouts. A related situation is the white-eyed fracture, something seen in children or young adults, said Dr. Mazzoli. “They have a blowout, with entrapment, but perhaps without many signs, such as swelling, ecchymosis or hemorrhage—so the eye is ‘white and quiet’ even in the presence of a fracture. The inclination might be to send the patient home with ice compresses, but you want to think about the mechanism, the energies and directions of the insult. And since exams on kids can be frustrating, you have to look carefully for diplopia and entrapment. You should probably err on the side of getting a scan.”
Two emergent situations. Ordinarily, orbital fractures are not critical emergencies. But there are two exceptions.
- Oculocardiac reflex. “One emergent situation is when you can provoke the oculocardiac reflex,” said Dr. Mazzoli. “The oculocardiac reflex can show up in any fracture, and this truly is an emergency. If the inferior rectus is herniated, and the patient tries to look up to compensate for his diplopia, he will be tugging on that muscle. And in so doing he may experience nausea and bradycardia, sometimes so profound that he ends up asystolic. Even if the fracture could wait a few days, the syncope obviously cannot. This should command immediate attention.”
- Roof fracture. Another potential emergency involves the roof, not the floor, of the orbit. Even in the context of floor fractures, Dr. Mazzoli highlighted this contingency in children because roof fractures are much more common for them than for adults. “That’s because they go headfirst over handlebars, and tend to do a forehead plant. And since kids don’t yet have a well-developed frontal sinus, what gives is the orbital roof. The V1 nerve runs through the roof, and if it’s damaged, you will find numbness along the scalp or forehead. It’s important to have a high index of suspicion in kids, so again, I’m more likely to err on the side of getting a CT.”
Hail the Heroic Floor
Gently concave near the orbital rim but growing convex postequatorially, the sloping, triangular orbital floor is the shortest and one of the thinnest of the four walls that frame the orbital cavity. Formed by the confluence of the zygomatic, maxillary and palatine plates and suspended above the maxillary sinus, the orbital floor humbly discharges its lifelong mission to hold aloft the human eye.
Aloft, that is, until a sixth-inning foul ball decides home is an eye socket. In spite of the severity of his injuries, however, Juan Encarnacion’s globe was not ruptured, and that is consistent with a pattern noticed by many trauma specialists, said Dr. Braverman. “At what point does the fracture itself perhaps allow for the dissipation of energy so that the globe doesn’t rupture? This is something we like to discuss, but we don’t know what the in vivo fail points are for either the globe or orbit.”
A gift from our ancestors? The cranial and facial architecture of primates is beautifully arranged to protect the brain and eyes from the impacts of fights and falls, and, in that light, Drs. Braverman and Kuhn allow for an intriguing possibility: The propensity of the floor to fail before the eyewall fails could be a strategy of natural selection, protecting the globe from worse trauma by releasing pressure from the orbit. Serious though they are, floor fractures may have offered a survival advantage in human evolution, since a ruptured globe would have more drastically impaired the victim’s ability to find food or escape predators.
“The floor can indeed be a safety mechanism that releases some of the energy that otherwise would have ruptured the globe,” said Dr. Kuhn. “A blunt impact allows the eyeball some room for escaping injury, since the orbit, of course, is larger than the globe.” Of course, a floor fracture would still have been a problem, Dr. Kuhn noted. “The inferior rectus muscle can get trapped in the fracture. But in evolution, if the choice is between a sunken globe and an irreparably ruptured globe, some survival advantage is clear.”
Inklings with applications. Anthropologic curiosity aside, this question could have valuable clinical applications. “If there is a relationship between globe ruptures and orbit fractures, and if perhaps the fractures are energy-release mechanisms, then we could make some predictions,” Dr. Braverman said. “When we don’t see a ruptured globe after a serious blow, are we more likely to see floor fractures? I always tell my residents to ask the patient ‘What were you hit with? Were you hit more than once?’ I think we can learn tremendously by dissecting the trauma mechanism. It can tell us where to look for more damage, whether to consider a surgical exploration and how urgently to proceed.”
Surgical Repair: When and How?
The globe comes first. Orbital fractures are often accompanied by intraocular injuries, even if the globe remains intact, according to Dr. Mazzoli. “It’s just the nature of the trauma that a serious impact can damage the eyeball as well as the bony socket. Any globe injury, like retinal detachment, should be investigated first because just by manipulating the periorbital tissues to fix a fracture you can make the intraocular condition worse.”
Then a game plan. “In my mind, the indications for fixing a floor fracture,” said Dr. Custer, “are if the patient has double vision related to probable muscle or soft-tissue entrapment, or if they have cosmetically or functionally significant enophthalmos. Traditionally we have watched patients for some time, hoping for improvement, but more and more we are moving toward early surgery in patients for whom it’s clearly needed. After several weeks the soft tissue is very adherent to the fracture site, and freeing up the soft tissue and repositioning it is very difficult. Basically we are trying to compress the time between trauma and repair in those patients.”
In the OR. The surgical entry of choice depends on the severity of the fracture and concomitant ocular trauma. “Some fractures require a combination of approaches in order to get the proper exposure,” Dr. Mazzoli said. “I think most of us are using a transconjunctival approach to the floor instead of transcutaneous, as it seems the chances of ectropion are lower. If the medial wall needs exploration, it’s relatively easy to extend this into a transcaruncular approach as well. For really large fractures, some surgeons will add a transantral exposure, pushing soft tissues up into the orbit from one direction while pulling them up from the other.”
Dr. Braverman agreed. “My preferred approach to the orbit floor is transconjunctival. I also find that a short course of oral prednisone preoperatively is helpful in reversing the inflammation and edema that can make operating in the inferior orbit a challenge.”
In any approach, Dr. Mazzoli warns surgeons to monitor the patient’s pupil continuously during the surgery, and to take extraordinary care with V2, the neurovascular bundle that travels through a canal in the floor. “That canal is lined with periosteum, and as we go in to repair a broken floor, it’s easy to confuse tissue that you want to tug out, with the nerve that you definitely do not want to tug out. These tissues can be almost indistinguishable, so you have to know the anatomy.”
Replacing the floor altogether. “Sometimes the floor is so devastated that all you have is a huge communication between the socket and the sinus below,” Dr. Mazzoli said. “We have to completely reconstruct the floor to keep the globe and soft tissues in the orbit. And to do that, we need a plate that can be cantilevered over the sinus from the rim.”
In these cases, Dr. Mazzoli said that titanium rim and floor plates and porous polyethylene floor plates have offered wonderful technological improvements over wire, silicone sheeting and calvarial bone. “These days, we tend to use titanium microplates on the rim and porous polyethelene for the floor, even if we have to anchor the polyethelene to the titanium in order to cantilever a plate out over large fractures. Actually, in a lot of cases the best solution is a combination: a porous polyethylene sandwich with a titanium mesh embedded inside it.”
The prospect of a plastic and metal sandwich saving a patient’s vision left Dr. Mazzoli especially satisfied. “That’s sweet,” he said. “Really sweet.”
1 Vinger P. F. et al. Arch Ophthalmol 1999; 117(3):354–358.
2 Bullock, J. D. et al. Trans Am Ophthalmol Soc 1999;97:87–113.
3 Ophthalmic Care of the Combat Casualty (Falls Church, Virginia: Office of The Surgeon General, Department of the Army, 2003.)