Fracture at the surgical neck of the humerus most often injures which nerve?

Fracture at the surgical neck of the humerus most often injures which nerve?

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

Answer: (D)

The important idea is the close relationship between the surgical neck of the humerus and the axillary nerve. The axillary nerve runs right near the joint as it courses through the quadrangular space with the posterior circumflex humeral artery, so a fracture in that region commonly injures it. When the axillary nerve is damaged, the deltoid and teres minor muscles weaken, leading to difficulty or inability to abduct the arm beyond about 15 degrees and a loss of sensation over the lateral shoulder (the regimental badge area). By contrast, the radial nerve is more at risk with midshaft fractures where it travels in the radial groove, and the median and ulnar nerves are typically affected by injuries at different sites (like the elbow or wrist). That proximity makes axillary nerve injury the most likely consequence of a fracture at the surgical neck.

The important idea is the close relationship between the surgical neck of the humerus and the axillary nerve. The axillary nerve runs right near the joint as it courses through the quadrangular space with the posterior circumflex humeral artery, so a fracture in that region commonly injures it. When the axillary nerve is damaged, the deltoid and teres minor muscles weaken, leading to difficulty or inability to abduct the arm beyond about 15 degrees and a loss of sensation over the lateral shoulder (the regimental badge area). By contrast, the radial nerve is more at risk with midshaft fractures where it travels in the radial groove, and the median and ulnar nerves are typically affected by injuries at different sites (like the elbow or wrist). That proximity makes axillary nerve injury the most likely consequence of a fracture at the surgical neck.