Blow out fracture of orbit involved ?
**Core Concept**
A blow out fracture of the orbit involves a traumatic injury to the bones surrounding the eye, specifically the orbital floor or medial wall, leading to a communication between the orbit and the adjacent paranasal sinuses. This type of fracture can result in entrapment of orbital contents, such as the inferior rectus muscle, due to the increased pressure within the orbit.
**Why the Correct Answer is Right**
The correct answer is related to the anatomy of the orbit and the consequences of a blow out fracture. When the orbital floor is fractured, it allows the orbital contents to herniate into the maxillary sinus, potentially entrapping the inferior rectus muscle. This can lead to limited eye movement in the downward direction (inferior gaze). The inferior rectus muscle is responsible for the downward movement of the eye, and its entrapment can cause symptoms such as diplopia (double vision), especially when looking downward.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify the correct anatomical structure involved in a blow out fracture of the orbit. While the lacrimal bone is part of the orbit, it is not typically involved in this type of fracture.
* **Option B:** This option is incorrect because the nasal bone is not part of the orbital floor or medial wall, and is not typically involved in a blow out fracture of the orbit.
* **Option C:** This option is incorrect because the zygomatic bone is part of the orbital floor, but it is not the most commonly involved structure in a blow out fracture of the orbit.
* **Option D:** This option is incorrect because the sphenoid bone is not typically involved in a blow out fracture of the orbit.
**Clinical Pearl / High-Yield Fact**
A key feature of a blow out fracture of the orbit is the presence of enophthalmos (sinking of the globe of the eye into the orbit), which can be a result of the herniation of orbital contents into the adjacent paranasal sinuses.
**Correct Answer:** C. Zygomatic bone is not the correct answer.