After a stab wound injury on shoulder, a man got ‘pointing index’ while trying to make fist. The nerve injured is:
**Core Concept**
The question tests knowledge of peripheral nerve injuries, specifically those affecting the upper limb. The **radial nerve**, **median nerve**, and **ulnar nerve** are the primary nerves responsible for hand and finger movements.
**Why the Correct Answer is Right**
The 'pointing index' sign is characteristic of a specific nerve injury. When a person tries to make a fist but ends up pointing with their index finger, it indicates weakness of the lateral two lumbricals and the thenar muscles, which are primarily innervated by the **median nerve**. This occurs because the **median nerve** supplies the flexor digitorum profundus (except the ulnar half), flexor digitorum superficialis, and the thenar muscles, which are crucial for fist formation.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because the radial nerve primarily controls wrist extension and supination.
**Option C:** Incorrect as the ulnar nerve supplies the medial half of the flexor digitorum profundus and the intrinsic muscles of the hand (except thenar muscles and lateral two lumbricals).
**Clinical Pearl / High-Yield Fact**
The 'pointing index' or 'OK sign' is a classic clinical sign of **median nerve** injury, which can occur from various traumas, including stab wounds or fractures. Recognizing this sign is crucial for diagnosing and managing median nerve injuries.
**Correct Answer:** Correct Answer: B. Median nerve.