Nerve injured with fracture of the surgical neck of the humerus?

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

Answer: (D)

The axillary nerve is the one at risk with a fracture of the surgical neck of the humerus because it wraps around that region in the quadrangular space to reach the deltoid and teres minor muscles, and it gives sensation to the skin over the lateral shoulder. When this nerve is injured, the deltoid can’t contract effectively, so arm abduction beyond the first 15 degrees is lost and the shoulder may appear flat. Sensation over the lateral shoulder (regimental badge area) can also be diminished. By contrast, the other nerves aren’t typically affected by a fracture at the surgical neck: the musculocutaneous nerve runs in the anterior arm, the radial nerve is in the radial groove, and the median nerve travels more medially and toward the forearm. Thus, loss of axillary function best explains injury at the surgical neck.