National Physical Therapy Examination (NPTE) Practice Exam

After a fall resulting in a fracture in the middle third of the humerus, which nerve is most likely compromised?

1. Radial nerve

2. Ulnar nerve

3. Median nerve

4. Musculocutaneous nerve

The correct answer is: Radial nerve

When a fracture occurs in the middle third of the humerus, it is most likely to impact the radial nerve. The radial nerve runs in close proximity to the humerus, particularly around the radial groove located on the posterior aspect of the bone. A mid-shaft humeral fracture can cause direct damage to the nerve as well as result in secondary effects like swelling or hematoma formation that can put pressure on the nerve. Injuries to the radial nerve can lead to conditions such as wrist drop, where the individual is unable to extend the wrist and fingers, indicating the nerve's role in controlling the extensor muscles of the forearm. The other nerves listed—ulnar, median, and musculocutaneous—are associated with different regions and functions and are less likely to be affected by a fracture in this area of the humerus. Understanding anatomy and the location of these nerves in relation to the humerus is crucial for recognizing potential nerve injuries following arm fractures. In this case, the anatomy of the radial nerve's path along the humerus makes it the most likely candidate for compromise following a mid-shaft humeral fracture.