A 30-year-old male underwent excision of the right radial head. Following surgery, the patient developed in ability to extend the fingers and thumb of the right hand. He did not have any sensory deficit. Which one of the following is the most likely cause:-
A 30-year-old male underwent excision of the right radial head. Following surgery, the patient developed in ability to extend the fingers and thumb of the right hand. He did not have any sensory deficit. Which one of the following is the most likely cause:-
💡 Explanation
## **Core Concept**
The question tests the understanding of the **radial nerve's** role in hand function, specifically its involvement in finger and thumb extension. The radial nerve innervates the **extensor muscles** of the wrist and fingers.
## **Why the Correct Answer is Right**
The correct answer, **posterior interosseous nerve (PIN) injury**, is a branch of the radial nerve that specifically supplies the muscles responsible for finger and thumb extension, namely the **extensor digitorum**, **extensor indicis**, and **extensor pollicis longus**. Injury to the PIN during radial head excision can lead to an inability to extend the fingers and thumb without affecting sensation, as the PIN is purely motor.
## **Why Each Wrong Option is Incorrect**
- **Option A:** Injury to the **median nerve** would primarily affect thumb opposition, flexion of the fingers, and sensation over the palmar surface of the thumb, index, and middle fingers, not finger and thumb extension.
- **Option B:** Damage to the **ulnar nerve** would result in difficulties with finger spreading and adduction, and intrinsic muscle function of the hand, not specifically impairing finger and thumb extension.
- **Option D:** A **radial nerve injury** proximal to the PIN branch would likely cause wrist drop (inability to extend the wrist) and possibly some sensory deficits over the back of the hand or the first web space, which is not the case here.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the **posterior interosseous nerve (PIN) syndrome** or injury presents with weakness or paralysis of finger and thumb extension but spares wrist extension (which is primarily mediated by the **extensor carpi radialis brevis** and **extensor carpi radialis longus**, innervated by the radial nerve before the PIN branch). This condition is often associated with specific activities or trauma, such as **radial head fractures** or **surgical complications**, as seen in this case.