Which of the following movements will be affected if the greater tubercle of the humerus is lost:
**Core Concept**
The **greater tubercle of the humerus** is a critical anatomical structure that serves as an insertion point for several muscles of the rotator cuff. It plays a significant role in shoulder movements, including abduction, internal rotation, and external rotation.
**Why the Correct Answer is Right**
The correct answer is related to the function of the muscles inserting on the greater tubercle, specifically the **supraspinatus**, **infraspinatus**, and **teres minor** muscles. These muscles are responsible for **abduction**, **external rotation**, and **adduction** of the shoulder joint, respectively. Loss of the greater tubercle would compromise the insertion of these muscles, thereby affecting their functions.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the movement it represents is not solely dependent on the integrity of the greater tubercle.
**Option B:** Similarly, this option is incorrect as the greater tubercle's primary role is not in this movement.
**Option C:** This option is also incorrect because, although related to shoulder function, it is not the most directly affected movement by the loss of the greater tubercle.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that the **rotator cuff muscles** (supraspinatus, infraspinatus, teres minor, and subscapularis) are crucial for stabilizing the shoulder joint and enabling a wide range of movements. Damage to any part of the rotator cuff, including the greater tubercle, can lead to significant functional impairment.
**Correct Answer:** Correct Answer: D. External Rotation.