Injury at the midshaft of the humerus predominantly involves which nerve?

• A. Radial nerve injury
• B. Median nerve injury
• C. Axillary nerve injury
• D. Ulnar nerve injury

Answer: (A)

The radial nerve is the structure most at risk with a midshaft humeral fracture because it runs in the spiral groove right along the posterior aspect of the humerus at that level. When this nerve is injured there is a loss of motor function to the extensor muscles of the forearm, leading to a classic wrist drop and weakness of finger extension, along with sensory changes on the dorsum of the hand from the superficial branch. The other nerves don’t typically run through the midshaft region in a way that makes them the main structure at risk there: the axillary nerve is near the surgical neck, the median nerve is more associated with injuries around the elbow or carpal region, and the ulnar nerve crosses near the medial epicondyle. So, injury at the midshaft predominantly involves the radial nerve.