In 1957, Byron Smith, MD, and William F. Regan, MD, coined the term blowout fracture to describe the mechanism of injury resulting from the impact of a blunt object hitting the orbital soft tissues of a cadaver. Specifically, the resultant increase in hydraulic pressure caused the thin internal walls of the orbit to fracture, and the displaced soft tissues became incarcerated, producing enophthalmos along with restricted mobility.1
Causes and diagnosis
Two mechanisms are known to cause a blowout fracture. One is the hydraulic pressure described previously, which is considered an orbital hydrostatic force created when a force on the globe in an anterior to posterior direction results in expansion in its equatorial diameter. This elastic force jackhammers the orbital floor, blowing the bone out into the sinus. The orbital floor is the shortest and one of the thinnest of the four walls that comprise the orbital cavity. A second mechanism is a blow to the orbital rim or zygoma that leads to a bone-to-bone transmission of energy known as the mechanical buckling model.2
The diagnosis of a blowout fracture for the two decades since its identification was based upon plain radiographs and tomography. Treatment recommendations varied widely from early surgical intervention for all fractures to the opposite extreme of prolonged observation. Surgery was then reserved for late enophthalmos or persistent diplopia. With the emergence of computed tomography scanning in the 1980s and 1990s, this debate narrowed and resulted in an approach where large fractures with a high likelihood of enophthalmos were operated on within the first two weeks.1
At least one emergent situation requires intervention: a fracture that results in an oculocardiac reflex. This reflex can show up in any fracture and is truly an emergency. In 1908, both Giuseppe Dagnini in Bologna, Italy, and later that year Bernhard Aschner in Vienna, Austria, independently reported the cardiac depressor reflex that may result in nausea, significant bradycardia, a junctional rhythm, asystole, and death. This reflex has an afferent limb via the trigeminal nerve and an efferent limb via the vagus nerve. The triggering stimulus is traction on the extraocular muscles.3 When the inferior rectus muscle is entrapped in the orbital floor after a blowout fracture, diplopia results. The natural response to overcoming diplopia is attempting to look up with the entrapped eye. This upward gaze tugs on the extraocular muscle and may elicit this reflex.
To examine the occurrence of orbital floor blowout fractures in the National Trauma Data Bank® (NTDB) research dataset admissions year 2014, medical records were searched using the International Classification of Diseases, Ninth Revision, Clinical Modification diagnoses codes. Specifically searched were records that contained the diagnosis codes of 802.6 (closed fracture of orbital floor: blow-out) or 802.7 (open fracture of orbital floor: blow-out). A total of 23,478 records were found, 19,816 of which contained a discharge status, including 14,520 patients discharged to home, 2,652 to acute care/rehab, and 1,784 sent to skilled nursing facilities; 860 died. Of these patients, 69.6 percent were male, on average 45.4 years of age, had an average hospital length of stay of 6.6 days, had an intensive care unit length of stay of 6.6 days, had an average injury severity score of 15.5, and were on the ventilator for an average of seven days (see Figure 1). The top three mechanisms accounting for almost 90 percent of the injuries were the blunt mechanism of motor-vehicle related, 36.1 percent; fall, 28.2 percent; and struck by, against, 22.7 percent (see Figure 2).
Advice for avoiding blowout fractures
One of the hazards of playing baseball is being hit by a foul ball. No one knows this better than Juan Encarnacion, outfielder for the St. Louis Cardinals. In 2007, he was waiting to pinch- hit in the on-deck circle when he was struck by a foul ball. He suffered a devastating orbital fracture while his globe remained intact.4 Spectators, too, are at risk of being struck by foul balls.
It is important to keep your head up and watch out for foul balls. However, if one does get hit in the eye and sustains a blowout fracture, it is advisable to avoid the temptation of an upward gaze to correct the resultant diplopia. If not, one could look up and die as a result of the oculocardiac reflex.
Throughout the year, we will be highlighting these data through brief monthly reports published in the Bulletin. The NTDB Annual Report 2015 is available on the ACS website as a PDF file. In addition, information is available on our website about how to obtain NTDB data for more detailed study. If you are interested in submitting your trauma center’s data, contact Melanie L. Neal, Manager, NTDB, at email@example.com.
Statistical support for this article has been provided by Crystal Caden-Price, Data Analyst, NTDB.
- Harris G. Orbital blow-out fractures: Surgical timing and technique. 2006;20(10):1207-1212. Available at: www.nature.com/eye/journal/v20/n10/full/6702384a.html. Accessed January 24, 2016.
- Smith D. Blowout! Managing the orbital floor fracture. Available at: www.aao.org/eyenet/article/blowout-managing-orbital-floor-fracture?NovemberDecember-2007. Accessed January 24, 2016.
- Oculocardiac reflex: Afferent path. Available at: www.openanesthesia.org/oculocardiac_reflex_afferent_path. Accessed January 24, 2016.
- Associated Press. Doctor says Encarnacion’s eye injury is “worst trauma I’ve seen.” Available at: http://espn.go.com/mlb/news/story?id=3002503. Accessed January 24, 2016.