**Colles' Fracture Displacement**

**Core Concept**
Colles' fracture is a type of fracture at the distal end of the radius bone in the forearm, typically occurring when a person falls onto an outstretched hand. The fracture often results in displacement of the bone fragments. The displacement patterns in Colles' fracture are crucial for diagnosis and treatment planning.

**Why the Correct Answer is Right**
In Colles' fracture, the typical displacement is dorsal angulation, also known as volar tilt, where the distal fragment of the radius bone is displaced dorsally and the wrist joint is tilted in a volar direction. This displacement is due to the force of the fall causing the bone to break and the distal fragment to be displaced dorsally. The dorsal angulation can lead to a decrease in the wrist's range of motion and cause pain.

**Why Each Wrong Option is Incorrect**
* **Option A:** The correct displacement in Colles' fracture is dorsal angulation, not volar angulation. Volar angulation would be an incorrect displacement pattern for a Colles' fracture.
* **Option B:** Radial shortening is a possible complication of Colles' fracture, but it is not a characteristic displacement pattern. The primary displacement in Colles' fracture is dorsal angulation.
* **Option C:** Ulnar variance refers to the difference in length between the radius and ulna bones. While ulnar variance can be affected in Colles' fracture, it is not a displacement pattern characteristic of this type of fracture.

**Clinical Pearl / High-Yield Fact**
In Colles' fracture, the displacement pattern can be remembered using the mnemonic "DASH": Dorsal angulation, Abduction, Shortening, and Hooking of the distal fragment.

**Correct Answer: A. Volar angulation**