Nerve injured with fracture of shaft of humerus?

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

Answer: (D)

The radial nerve is most at risk with a fracture of the humeral shaft because it runs in the radial groove along the posterior surface of the bone. This nerve supplies most of the extensor muscles of the arm and forearm, so injury here typically causes weakness or loss of wrist and finger extension (a wrist drop). Sensation from the dorsum of the hand is also affected, especially over the lateral part.

Injury to other nerves would point to different fracture locations: the axillary nerve is commonly injured with a surgical neck fracture of the humerus, the median nerve with injuries around the elbow or carpal tunnel, and the ulnar nerve with injuries near the medial epicondyle. Thus, a midshaft fracture of the humerus most characteristically injures the radial nerve.