During Wartenberg's test, which movement is resisted to assess ulnar nerve entrapment?

• A. Fifth digit adduction
• B. Thumb opposition
• C. Pinky abduction
• D. Wrist flexion

Answer: (A)

The test targets the interossei muscles that adduct the little finger, which are controlled by the ulnar nerve. In Wartenberg's test, you resist the adduction of the little finger toward the ring finger. If the ulnar nerve is entrapped, these interossei are weak, so the little finger cannot adduct adequately and tends to stay abducted because the opposing abductor digiti minimi remains unopposed. This makes resisting fifth digit adduction the most direct way to reveal ulnar neuropathy. Movements like thumb opposition are mediated by the median nerve, little finger abduction involves the abductor digiti minimi but the test focuses on adduction, and wrist flexion involves different muscles not specific to the interossei tested here.