## **Core Concept**
The question tests knowledge of orthopedic injuries, specifically the nerves commonly affected in elbow dislocations. Posterior dislocation of the elbow is a type of injury where the radius and ulna bones of the forearm are displaced posteriorly relative to the humerus. This type of injury can cause damage to the surrounding nerves.

## **Why the Correct Answer is Right**
The **ulnar nerve** is the most commonly injured nerve in posterior dislocation of the elbow. This is because the ulnar nerve runs through a narrow and relatively fixed path, the cubital tunnel, at the elbow. In posterior dislocations, the nerve can be stretched or directly damaged as the elbow joint is disrupted. The ulnar nerve's anatomical location makes it particularly susceptible to injury in this type of dislocation.

## **Why Each Wrong Option is Incorrect**
* **Option A:** The median nerve can be injured in elbow injuries but is less commonly associated with posterior dislocations compared to the ulnar nerve. The median nerve runs through the anterior aspect of the elbow and is more commonly injured in fractures or dislocations that directly affect the anterior elbow region.
* **Option B:** The radial nerve can also be injured in elbow injuries, particularly in fractures of the humerus. However, it is not the most commonly injured nerve in posterior dislocations of the elbow.
* **Option D:** The musculocutaneous nerve is less commonly injured in elbow dislocations and is more associated with injuries to the anterior compartment of the arm.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the ulnar nerve is particularly at risk in elbow injuries due to its superficial location at the elbow, passing through the cubital tunnel. Clinicians should have a high index of suspicion for ulnar nerve injury in patients with posterior elbow dislocations.

## **Correct Answer:** . ulnar nerve