Orbital blowout fracture
An orbital blowout fracture of the floor of the left orbit.
|Classification and external resources|
A blowout fracture is a fracture of the walls or floor of the orbit. Intraorbital material may be pushed out into one of the paranasal sinuses. This is most commonly caused by blunt trauma of the head, generally personal altercations. Orbital floor fractures were investigated and described by MacKenzie in Paris in 1844 and the term blow out fracture was coined in 1957 by Smith & Regan, who were investigating injuries to the orbit and resultant inferior rectus entrapment, by placing a hurling ball on cadaverous orbits and striking it with a mallet. The force of a blow to the orbit is dissipated by a fracture of the surrounding bone, usually the orbital floor and/or the medial orbital wall. Serious consequences of such injury include diplopia in upgaze where there is significant damage to the orbital floor. In blowout fractures, the medial wall is fractured indirectly. When an external force is applied to the orbital cavity from an object whose diameter is larger than that of the orbit, the orbital contents are retropulsed and compressed. The consequent sudden rise in intraorbital pressure is transmitted to the walls of the orbit, which ultimately leads to fractures of the thin medial wall and/or orbital floor. Theoretically, this mechanism should lead to more fractures of the medial wall than the floor, since the medial wall is slightly thinner (0.25 mm vs 0.50 mm). However, it is known that pure blowout fractures most frequently involve the orbital floor. This may be attributed to the honeycomb structure of the numerous bony septa of the ethmoid sinuses, which support the lamina papyracea, thus allowing it to withstand the sudden rise in intraorbital hydraulic pressure better than the orbital floor.
Some clinically observed signs include:
- Restricted vertical movement of the eye
- Subconjunctival hemorrhage
- Swollen lid
- Loss of sensation over upper cheek area
- Periorbital (around eye socket) ecchymosis
Common medical causes of blowout fracture may include:
- Direct orbital blunt injury
- Sports' injury (squash ball, tennis ball etc.)
- Motor vehicle accidents
- Facial trauma
The most commonly fractured area in blowout fracture is the floor of orbit. Diagnosis is based on clinical and radiographic evidence. Circumorbital (around eye socket) ecchymoses and subconjunctival hemorrhage indicate a possible fracture. On Water's view radiograph, polypoid mass can be observed hanging from the floor into the maxillary antrum, classically known as teardrop sign, as it usually is in shape of a teardrop. This polypoid mass consists of herniated orbital contents, periorbital fat and inferior rectus muscle. The affected sinus is partially opacified on radiograph. Air-fluid level in maxillary sinus may sometimes be seen due to presence of blood. CT scan can also show any soft tissue and bone involvement. Fracture of medial wall can produce subcutaneous emphysema, especially when blowing the nose or while sneezing. Lucency in orbits (on a radiograph) usually indicate orbital emphysema.
Surgery is indicated if
- Enophthalmos greater than 2mm
- Double vision on primary or inferior gaze
- Entrapment of extraocular muscles
- Fracture greater than 50% of the orbital floor
When not surgically repaired (for the above indications), most blowout fractures heal spontaneously without significant consequence. Corticosteroid therapy may be used to reduce swelling. Antibiotics are usually given as prevention of infection. Surgical repair of a "blowout" is rarely undertaken immediately; it can be safely postponed for up to two weeks, if necessary, to let the swelling subside. Surgery to place an orbital implant leaves little or no scarring and the recovery period is usually brief. Hopefully, the surgery will provide a permanent cure, but sometimes it provides only partial relief from double vision or a sunken eye
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