**Question:** A rock climber falls on his shoulder, resulting in a chipping off of the lesser tubercle of the humerus. Which of the following structures would most likely have structural and functional damage?

A. Rotator cuff tendons
B. Glenoid labrum
C. Subscapularis muscle
D. Deltoid muscle

**Core Concept:**

The lesser tubercle of the humerus is a bony projection on the humerus that serves as an attachment site for the long head of the biceps brachii muscle. When a person falls on their shoulder, the greater tubercle of the humerus, which is more distal and less rigid, is more susceptible to injury. In this scenario, the lesser tubercle would also be at risk due to its attachment site.

**Why the Correct Answer is Right:**

The correct answer is B (Glenoid labrum) because the lesser tubercle is a part of the bony structure and does not have significant involvement in shoulder function. The glenoid labrum is a fibrocartilaginous ring surrounding the glenoid fossa of the scapula, providing increased depth and stability to the glenohumeral joint. In this context, the structural and functional damage would be more associated with the glenoid labrum than the other options.

**Why Each Wrong Option is Incorrect:**

A. Rotator cuff tendons (A) are essential for shoulder stability and function, but they attach to the greater tubercle of the humerus, not the lesser tubercle. Thus, the damage to rotator cuff tendons would not involve the lesser tubercle.

C. Subscapularis muscle (C) is another shoulder stabilizer, but its attachment site is different from the lesser tubercle and rotator cuff tendons. Damage to the subscapularis muscle would not be directly related to the lesser tubercle.

D. Deltoid muscle (D) is a shoulder extensor but does not have any direct attachment site to the lesser tubercle. Damage to the deltoid muscle would not involve the lesser tubercle.

**Clinical Pearl:**

The glenoid labrum is a crucial structure for shoulder stability and function, as it plays a significant role in maintaining the depth of the glenohumeral joint and providing a larger contact area for the humeral head, facilitating a more secure fit between the humerus and scapula. Injuries to the glenoid labrum can result in shoulder instability and impingement syndrome.