Axillary nerve injury most significantly impairs which shoulder movement?

Axillary nerve injury most significantly impairs which shoulder movement?

• A. Extension of the elbow
• B. Abduction of the arm
• C. Flexion of the wrist
• D. Pronation

Answer: (B)

Damage to the axillary nerve mainly disrupts the deltoid muscle, which is the primary mover of shoulder abduction. While the initial small portion of abduction (about the first 15 degrees) is helped by the supraspinatus, the deltoid takes over to lift the arm laterally. So when the axillary nerve is injured, abduction of the arm is most significantly impaired. Other movements listed involve different nerves: extending the elbow relies on the radial nerve, wrist flexion on the median/ulnar nerves, and pronation on the median nerve. The key deficit with axillary nerve injury is loss of shoulder abduction due to deltoid dysfunction.

Damage to the axillary nerve mainly disrupts the deltoid muscle, which is the primary mover of shoulder abduction. While the initial small portion of abduction (about the first 15 degrees) is helped by the supraspinatus, the deltoid takes over to lift the arm laterally. So when the axillary nerve is injured, abduction of the arm is most significantly impaired.

Other movements listed involve different nerves: extending the elbow relies on the radial nerve, wrist flexion on the median/ulnar nerves, and pronation on the median nerve. The key deficit with axillary nerve injury is loss of shoulder abduction due to deltoid dysfunction.