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Froment's sign is a physical examination of the hand to test for palsy of the ulnar nerve which results in reduced functionality and muscle weakness of the pinch grip. It tests the strength of the adductor pollicus of the thumb, which is innervated by the ulnar nerve and is weakened in ulnar nerve palsy.
Froment's sign presents after damage to the ulnar nerve, which innervates the adductor pollicis and interossei muscles, which provide adduction of the thumb and extension of the interphalangeal joint. The flexor pollicis longus (innervated by the median nerve), will substitute for the adductor pollicis (innervated by the ulnar nerve) and cause the thumb to go into hyperflexion. Ulnar nerve palsy can be as a result of dysfunction at the cervical spine, elbow (cubital tunnel syndrome) or at the wrist (Guyons canal syndrome).
The patient is asked to make a strong pinch between the thumb and index finger and grip a flat object such as a piece of paper between the thumb and index finger. The examiner then attempts to pull the object out of the subject's hands. There is weakness of the adductor pollicus innervated by the ulnar nerve which would keep the IP joint relatively straight; instead, the FPL muscle which is innervated by the median nerve is substituted for the AP and will cause the IP joint to go into a hyperflexed position.
Similar to Froment’s sign, Jeanne’s sign indicates ulnar nerve palsy and is also seen in response to pinch forces. Instead of isolated thumb IP flexion, the IP flexion is accompanied by MP joint hyperextension.
This test has been described, but no studies were found that look at diagnostic properties
- Froment, J. “La prehension dans les paralysies, du nerf cubital et la signe du ponce.” Presse med.23 (1915): 409.
- Richardson J and Fabre G. Froment's Sign. Audiov Media Med, 2003
- Jeff G. Konin et al. Special Tests for Orthopedic Examination: Third Edition. Thorofare, NJ. SLACK Incorporated, 2006.
- Jeanne M. “La deformation du ponce la paralysie cubitale.” Bul Mem Soc Chir Paris 41 (1915): 703-19.