A 43-year-old man had a previous injury to his wrist. The ulnar nerve was severed, as indicated by which of the following?
**Core Concept**
The ulnar nerve injury is a type of peripheral nerve damage affecting the motor and sensory functions of the hand. The ulnar nerve is responsible for innervating the intrinsic muscles of the hand, specifically the interosseous muscles and the adductor pollicis.
**Why the Correct Answer is Right**
The ulnar nerve injury is characterized by the loss of function of the intrinsic muscles of the hand, leading to a condition known as "positive Froment's sign." This is due to the inability to adduct the thumb, which is normally mediated by the ulnar nerve. The patient will compensate for this by using the flexor pollicis longus muscle to adduct the thumb, resulting in a characteristic "pincer grasp" deformity. This is a classic clinical sign of ulnar nerve damage.
**Why Each Wrong Option is Incorrect**
**Option A:** Wrist extension weakness is more commonly associated with radial nerve damage.
**Option B:** Claw hand deformity is a feature of median nerve damage.
**Option C:** A positive Tinel's sign is a general indicator of nerve regeneration, not specific to ulnar nerve damage.
**Clinical Pearl / High-Yield Fact**
Remember that Froment's sign is a classic clinical indicator of ulnar nerve damage, and it is essential to assess the patient's ability to adduct the thumb to confirm the diagnosis.
**Correct Answer: C. A positive Tinel's sign is not specific to ulnar nerve damage, and a claw hand deformity is more indicative of median nerve damage.