A 20-year-old male sustains a closed mid-shaft fracture of the right humerus in a wrestling match. On physical examination, he is unable to extend his right wrist or fingers, and has sensory loss over the dorsal aspect of the first web space. Which nerve was injured?

Answer and explanation

Correct answer: B. Radial nerve

  1. Step 1: The radial nerve courses directly in the spiral groove along the posterior mid-shaft of the humerus.
  2. Step 2: Fractures in this location frequently cause neuropraxia or laceration of the radial nerve, presenting with classic wrist drop and dorsal first web space numbness.
Answer
Radial nerve.
Why not the others: 'Median nerve' injury results in loss of thumb opposition and sensory loss on the palmar surface of the lateral 3.5 digits; 'Ulnar nerve' injury causes claw hand deformity and numbness over the 5th digit; 'Axillary nerve' injury impairs deltoid abduction and sensation over the lateral shoulder.

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