Nerve injury most commonly associated with a humeral shaft fracture?

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

Answer: (D)

The nerve most likely to be injured with a humeral shaft fracture is the radial nerve because it travels right along the posterior humeral shaft in the spiral groove, making it particularly vulnerable to midshaft trauma. Injury to this nerve typically causes a wrist drop from weakness of the wrist and finger extensors, and sensory loss over the dorsoradial aspect of the hand (with the superficial branch).

The other nerves have different typical injury patterns: the axillary nerve is more at risk with injuries near the shoulder (surgical neck of the humerus), the median nerve is more commonly affected with supracondylar or more distal injuries of the humerus, and the ulnar nerve is associated with medial elbow/distal humerus injuries. So, in a humeral shaft fracture, radial nerve involvement is by far the most common.