Which sign is associated with anterior interosseous nerve entrapment?

• A. Benedictine sign
• B. Froment's sign
• C. Tinel's sign
• D. Phalen's sign

Answer: (A)

Anterior interosseous nerve entrapment causes motor weakness of the muscles that flex the thumb’s IP joint and the index finger’s DIP joint (flexor pollicis longus and the lateral half of flexor digitorum profundus). When the patient tries to pinch, these joints can’t flex properly, so the index finger and thumb don’t come together as they should. The resulting posture is a benediction-like hand, known as Benedictine (or Benedict sign), which is the classic sign of this nerve entrapment.

The other signs point to different nerves or conditions: Froment’s sign tests ulnar nerve palsy with compensatory flexion of the thumb’s IP joint due to loss of adductor pollicis; Tinel’s sign indicates nerve irritation at a compression site; Phalen’s sign is associated with carpal tunnel (median nerve).