Blowout fractures are caused by direct trauma to the
globe which causes an increase in intraorbital pressure and
decompression via fracture of the orbital floor.
Radiographically, fragments may be seen in the maxillary
sinus or there may be opacification of the maxillary sinus with
blood. Clinically, there may be diplopia on upward gaze due to
entrapment of the inferior rectus muscle.
Orbital fractures occur when the force generated by blunt
trauma exceeds the tolerances of the bony surfaces. Medial wall
fractures can occur either from direct injuries to the face or
indirectly as blowout fractures. When the fracture occurs as a
result of a direct injury, it is usually in conjunction with a naso-orbital
fracture, which results from direct application of blunt force to
the naso-orbital area. The most frequent cause of these naso-orbital
fractures is a motor vehicle accident that results in the face
impacting against the steering wheel or dashboard; additional causes
include blunt trauma from the fist or the elbow. Medial wall blowout
fractures are potential sequelae of blunt periorbital trauma. Common
causes for this type of medial wall fracture include fists, elbows,
shoe kicks, baseballs, and tennis balls, all of which have a
diameter greater than the orbital rim.
A naso-orbital fracture tends to consist of a comminuted,
depressed fracture involving the nasal bones, ethmoid sinuses, and
medial orbital walls. It occurs when a blow of sufficient force is
applied to the nasal bridge area. Such blunt trauma can cause the
medial wall to develop a fracture in 1 of 2 ways. First, when the
nasal bone fragments are projected backward, the thin lacrimal bone
and lamina papyracea are comminuted easily. The nasal bone and
frontal process of the maxilla may be displaced posteriorly into the
ethmoid sinus; as a result, an in-fracturing of the medial orbital
wall into the orbit occurs. Therefore, the compressive force causing
nasal fractures is a very important causative factor of pure medial
With 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.
Surgical repair is performed if the diplopia is unlikely to resolve
spontaneously, there is severe enophthalmus, or the fracture is so
large that the development of enophthalmus is likely.
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
OM 30 radiograph. This reveals herniation of fat into the left
maxillary sinus, due to an orbital floor fracture.
Useful Link: http://www.oculoplastics.com/topics/trauma/trauma_orbital_fracture.htm