**Core Concept**
The medial epicondyle of the humerus is a bony prominence on the inside of the elbow. It serves as an attachment point for several muscles and nerves, including the ulnar nerve. The ulnar nerve is a mixed nerve that provides motor and sensory innervation to the forearm and hand.

**Why the Correct Answer is Right**
The ulnar nerve is particularly vulnerable to injury in fractures of the medial epicondyle of the humerus due to its close proximity to the site of fracture. As the ulnar nerve passes posterior to the medial epicondyle, it is at risk of being stretched, compressed, or even transected during the fracture process. This can result in a range of symptoms, including numbness, tingling, and weakness in the hand.

**Why Each Wrong Option is Incorrect**
**Option A:** The anterior interosseous nerve is a branch of the median nerve and is not typically associated with injuries to the medial epicondyle of the humerus.
**Option B:** While the median nerve does pass through the cubital tunnel, which is close to the medial epicondyle, it is not the primary nerve at risk in this type of fracture.
**Option D:** The radial nerve is not typically associated with injuries to the medial epicondyle of the humerus, as it runs along the back of the humerus and is more commonly injured in fractures of the shaft of the humerus.

**Clinical Pearl / High-Yield Fact**
A key clinical correlation to remember is that the ulnar nerve is also at risk in other conditions that involve the medial aspect of the elbow, such as cubital tunnel syndrome or medial epicondylitis (golfer's elbow). This is because the ulnar nerve is often compressed or irritated in these conditions, leading to similar symptoms.

**✓ Correct Answer: C. Ulnar**