**Question:** Skyline view X-ray is useful in diagnosing -

A. Deltoid tubercle fracture
B. Acromioclavicular joint dislocation
C. Scapular spine fracture
D. Supraspinatus tendon tear

**Core Concept:** Skyline view X-ray is a specific radiographic view that highlights the scapular spine and the glenoid fossa, allowing for assessment of the structures in the glenohumeral joint.

**Why the Correct Answer is Right:**

The correct answer, **B. Acromioclavicular joint dislocation**, is chosen because the skyline view X-ray is particularly useful in evaluating the acromioclavicular joint. In this view, the glenoid fossa, coracoid process, and acromion are visualized, allowing for assessment of the joint and surrounding structures.

**Why Each Wrong Option is Incorrect:**

A. **Deltoid tubercle fracture (A)**: The skyline view is not particularly useful for diagnosing fractures of the deltoid tubercle, as this fracture is better assessed using the axillary view or the lateral view.

C. **Scapular spine fracture (C)**: While the skyline view can show fractures of the scapular spine, it is not as specific as other views, such as the axillary view, which provides a clearer view of the scapular spine.

D. **Supraspinatus tendon tear (D)**: The skyline view is not particularly useful for diagnosing supraspinatus tendon tears, as this injury is often best evaluated using the axillary or glenohumeral views.

**Clinical Pearl:** Skyline view X-rays are essential in assessing glenohumeral joint injuries, as they provide detailed information about the acromioclavicular joint, scapula, and coracoid process. However, they may not be as useful in evaluating fractures of the scapular spine or supraspinatus tendon tears. For these conditions, alternative views should be considered, such as the axillary or glenohumeral views.