**Question:** In extension type of supracondylar fracture, the usual displacement

A. Medial
B. Lateral
C. Anteroposterior
D. Posterior

**Core Concept:** Supracondylar fractures are a type of humerus fracture that occurs at or near the elbow joint. Extension type supracondylar fractures involve the bone being forced into extension while the elbow is bent. This results in a specific pattern of displacement.

**Why the Correct Answer is Right:** In an extension type supracondylar fracture, the usual displacement occurs in the anteroposterior (AP) direction. This is due to the force exerted on the humerus causing the fracture to move in the AP plane. This type of displacement allows for easy recognition on X-rays, as the fracture line will be visible on the AP view.

**Why Each Wrong Option is Incorrect:**

A. Medial displacement is incorrect as it would not result from a simple extension force applied to the elbow. Medial displacement is more commonly seen in flexion type fractures.

B. Lateral displacement is incorrect as it would not result from an extension force applied to the elbow. Lateral displacement is more commonly seen in flexion type fractures.

C. Posterior displacement is incorrect as it would not result from an extension force applied to the elbow. Posterior displacement is more commonly seen in flexion type fractures.

**Clinical Pearl:** Supracondylar fractures are a common fracture type in children, especially in falls from height. Early recognition and management are crucial to prevent neurological and vascular complications.

**Correct Answer:** D. Posterior

In the context of supracondylar fractures, the term "posterior" refers to the displacement direction that can occur in a flexion type fracture, where the humerus moves posteriorly due to the force applied to the elbow in flexion. Extension type fractures, like the one in this question, typically result in anteroposterior (AP) displacement, not posterior displacement.