Following anterior dislocation of the shoul-der, a pt develops weakness of flexion at elbow and lack of sensation over the lateral aspect forearm; nerve injured is:
**Core Concept**
The question tests the understanding of the anatomical relationship between the nerves and the shoulder joint, specifically the mechanism of injury in anterior dislocation of the shoulder and its effect on surrounding nerves.
**Why the Correct Answer is Right**
In an anterior dislocation of the shoulder, the humerus is displaced anteriorly, which can cause stretching or injury to the axillary nerve. The axillary nerve innervates the deltoid muscle, which is responsible for shoulder flexion, abduction, and external rotation, but not elbow flexion. However, the axillary nerve also gives off a branch that innervates the radial nerve via the posterior cord of the brachial plexus. The radial nerve is responsible for innervating the muscles that extend the wrist and fingers, but it also provides sensation to the back of the arm and the lateral aspect of the forearm. The injury to the axillary nerve can cause weakness of the deltoid muscle, leading to weakness of flexion at the elbow, and can also cause numbness or loss of sensation over the lateral aspect of the forearm due to damage to the branch of the radial nerve.
**Why Each Wrong Option is Incorrect**
**Option A:** The musculocutaneous nerve is responsible for innervating the biceps brachii and brachialis muscles, which are responsible for elbow flexion. It is not typically injured in an anterior dislocation of the shoulder.
**Option B:** The ulnar nerve is responsible for innervating the muscles of the forearm and hand, particularly those involved in fine motor movements and sensation over the medial aspect of the forearm and hand. It is not typically injured in an anterior dislocation of the shoulder.
**Option C:** The median nerve is responsible for innervating the muscles of the anterior forearm and hand, particularly those involved in flexion and opposition of the thumb. It is not typically injured in an anterior dislocation of the shoulder.
**Clinical Pearl / High-Yield Fact**
In anterior dislocation of the shoulder, the axillary nerve is at risk of injury due to its anatomical relationship with the shoulder joint. This can lead to weakness of the deltoid muscle and numbness or loss of sensation over the lateral aspect of the forearm.
**Correct Answer:** C. The radial nerve.