Following anterior dislocation of the shoulder, a patient develops weakness of flexion at elbow and lack of sensation over the lateral aspect forearm : nerve injured is –
## **Core Concept**
The question tests knowledge of peripheral nerve injuries, specifically those related to shoulder dislocation and their effects on motor and sensory functions. The nerves in question are branches of the brachial plexus, which can be injured during shoulder dislocations. The symptoms described point towards a specific nerve injury affecting elbow flexion and sensation over the lateral forearm.
## **Why the Correct Answer is Right**
The correct answer, **Musculocutaneous nerve (C)**, is implicated because this nerve is responsible for innervating the biceps brachii muscle, which is a primary flexor of the elbow. Damage to this nerve would result in weakness of elbow flexion. Additionally, the musculocutaneous nerve gives rise to the lateral antebrachial cutaneous nerve, which provides sensation to the lateral aspect of the forearm. Therefore, injury to this nerve would lead to the symptoms described: weakness of elbow flexion and sensory loss over the lateral forearm.
## **Why Each Wrong Option is Incorrect**
- **Option A (Axillary nerve):** This nerve primarily supplies the deltoid muscle and teres minor, and provides sensation to the shoulder region. It doesn't match the symptoms described.
- **Option B (Median nerve):** While the median nerve does contribute to elbow flexion (through innervation of the brachialis, to a lesser extent) and provides sensation to parts of the forearm and hand, the specific pattern of weakness and sensory loss doesn't exactly match that described.
- **Option D (Radial nerve):** This nerve is involved in wrist and finger extension and provides sensation to the back of the arm, forearm, and hand. Its injury wouldn't cause the specific symptoms mentioned.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the musculocutaneous nerve is often injured in anterior shoulder dislocations due to its anatomical course. Clinicians should be aware of this potential complication and assess for signs of nerve injury in patients with shoulder dislocations.
## **Correct Answer: C. Musculocutaneous nerve**