Explain why the tip of the thumb flexes when trying to grasp a piece of paper between the thumb and index finger in a client who has ulnar nerve paralysis

A. Because the flexor pollicis longus substitutes for the absent adductor pollicis muscle
B. Because the extensor pollicis longus is absent in ulnar nerve injuries
C. Because the index flexor tendons are absent in ulnar nerve injuries
D. Because the thumb opponens pollicis is absent in ulnar nerve injuries

ANS: A
One test for ulnar nerve paralysis involves asking a client to grasp a piece of paper between the thumb and index finger. When the examiner pulls away the paper, the tip of the thumb flexes because of the absence of the adductor pollicis muscle. This is called Froment's sign. If the met-acarpophalangeal (MP) joint of the thumb also extends at the same time, it is known as Jeanne's sign.