What does Froment’s sign indicate, and which nerve is involved?

Study for the NBCOT Hand Injuries and Intervention Test. Prepare with flashcards and multiple choice questions, each question offers hints and explanations. Get ready for success!

Froment’s sign demonstrates loss of adductor pollicis function, which is supplied by the ulnar nerve. When a person tries to pinch a piece of paper between the thumb and index finger, the adductor pollicis normally keeps the thumb adducted and the IP joint in line. If the ulnar nerve is impaired, the adductor pollicis is weak, so the person compensates by flexing the thumb’s IP joint through the flexor pollicis longus (innervated by the median nerve). This flexion of the IP joint during pinch is Froment’s sign and indicates ulnar nerve palsy, specifically weakness of the adductor pollicis.

Other options don’t fit this pattern: median nerve palsy affects thenar muscles and thumb opposition but not the specific adductor mechanism seen in Froment’s sign; radial nerve palsy presents with wrist drop; axillary nerve palsy affects shoulder abduction.