**Core Concept**
The medial epicondyle fracture is a type of elbow fracture that involves the medial condyle of the humerus. This region is anatomically close to the ulnar nerve, which passes through the cubital tunnel. The proximity of the ulnar nerve to the medial epicondyle makes it susceptible to injury during a fracture.

**Why the Correct Answer is Right**
The most common associated injury of a fracture medial epicondyle is ulnar nerve injury. The ulnar nerve can be stretched or even transected during the fracture, leading to symptoms such as numbness, tingling, and weakness in the hand. This is due to the close proximity of the ulnar nerve to the medial epicondyle and the cubital tunnel, which is a narrow space that contains the ulnar nerve. The ulnar nerve can be compressed or damaged during the fracture, leading to nerve injury.

**Why Each Wrong Option is Incorrect**
* **Option A:** Radial nerve injury is less common in medial epicondyle fractures, as the radial nerve is located on the opposite side of the elbow.
* **Option B:** Median nerve injury can occur in elbow fractures, but it is less common than ulnar nerve injury in medial epicondyle fractures.
* **Option C:** Brachial artery injury is a rare complication of elbow fractures and is not typically associated with medial epicondyle fractures.

**Clinical Pearl / High-Yield Fact**
The ulnar nerve is at risk of injury in medial epicondyle fractures due to its proximity to the fracture site and the cubital tunnel. Clinicians should be aware of this association and monitor patients for ulnar nerve symptoms after a medial epicondyle fracture.

**Correct Answer: C. Brachial artery injury is a rare complication of elbow fractures and is not typically associated with medial epicondyle fractures.