A patient is asked to pinch an object, usually a flat object such as a piece of paper, between the
thumb and index finger (pinch grip). The examiner then attempts to pull the object out of the subject's hand. • A person with notable weakness of the adductor pollicis due to advanced ulnar neuropathy will flex the thumb using the
flexor pollicis longus. • Froment sign is the
flexion of the
interphalangeal joint of the thumb rather than adduction of the entire thumb. • Note that the flexor pollicis longus is nearly always innervated by the
anterior interosseous branch of the median nerve. • Simultaneous hyperextension of the thumb
MCP joint is indicative of ulnar nerve compromise. This is also known as Jeanne's sign. ==Eponym==