Blow out fracture of orbit involves:
**Core Concept**
A blow out fracture of the orbit is a type of orbital injury characterized by a fracture of one or more walls of the orbit, typically due to a direct blow to the globe or surrounding bones. This type of fracture can lead to entrapment of extraocular muscles, enophthalmos, and diplopia.
**Why the Correct Answer is Right**
A blow out fracture of the orbit involves the thin walls of the orbit, particularly the orbital floor (lamina papyracea) or medial wall. The fracture occurs due to a sudden increase in intraorbital pressure, which can cause the thin orbital bones to be compressed and eventually fracture. The orbital floor is the most common site for blow out fractures, as it is the weakest point of the orbit. The lamina papyracea, a thin plate of bone that forms the orbital floor, can be compressed and fractured, leading to herniation of the orbital contents into the maxillary sinus.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not specify the type of fracture or the affected bones.
**Option B:** This option is incorrect as it is not a common type of orbital fracture.
**Option C:** This option is incorrect as it is not a characteristic feature of a blow out fracture of the orbit.
**Clinical Pearl / High-Yield Fact**
A blow out fracture of the orbit can be diagnosed using a CT scan with coronal and sagittal reconstructions, which can demonstrate the extent of the fracture and the presence of any entrapment of extraocular muscles.
**Correct Answer: C. Orbital floor (lamina papyracea) fracture.