flexion of the distal phalanx of the thumb when a sheet of paper is held between the thumb and index finger in ulnar nerve palsy.

Froment’s sign is a clinical test used to assess the strength and integrity of the adductor pollicis muscle, which is a muscle located in the hand that is responsible for adducting the thumb, or moving it toward the other fingers.

To perform the Froment’s sign test, the examiner asks the patient to grip a piece of paper or other thin object between the thumb and the side of the index finger, as if holding a piece of paper between the fingers. The examiner then tries to pull the paper away from the patient. In a person with normal strength in the adductor pollicis muscle, the thumb remains firmly pressed against the index finger, and the paper cannot be pulled away. However, in a person with weakness or paralysis of the adductor pollicis muscle, the thumb flexes at the interphalangeal joint and hyperextends at the metacarpophalangeal joint, resulting in a compensatory movement that allows the paper to be held against the side of the index finger. This is known as a positive Froment’s sign.

Froment’s sign is often used in the diagnosis of ulnar nerve palsy, a condition in which the ulnar nerve, which supplies the adductor pollicis muscle and other muscles in the hand, is damaged or compressed. Ulnar nerve palsy can cause weakness or paralysis of the adductor pollicis muscle, resulting in a positive Froment’s sign. The test is also used to assess other conditions that may affect the adductor pollicis muscle or the ulnar nerve.

Overall, Froment’s sign is a simple and non-invasive test that can provide useful information about the strength and function of the adductor pollicis muscle, and can be an important component of a comprehensive neurological examination.