A 26 year old engineering student presented to the emergency with pain in the wrist after a fall on an outstretched hand from the motorcycle travelling at a very high speed. Examination shows swelling, diffuse tenderness, deformity, and limited wrist movement. ‘Spilled teacup’ sign is seen on a PA view X-ray wrist. What is the likely diagnosis?

**Core Concept**
Displacement of the distal radius due to a fall on an outstretched hand is a common mechanism leading to a specific type of fracture. This type of injury is often associated with a characteristic radiographic appearance.

**Why the Correct Answer is Right**
The 'spilled teacup' sign on a PA view X-ray of the wrist is indicative of a Colles' fracture. This occurs when the distal fragment of the radius is displaced dorsally, resulting in a characteristic appearance on radiographs. The mechanism of injury, with a fall on an outstretched hand, is a classic cause of this type of fracture. The displacement of the distal fragment leads to a visible step-off on the lateral X-ray, which is a hallmark of this injury.

**Why Each Wrong Option is Incorrect**
* **Option A:** Scaphoid fracture - This type of fracture typically occurs after a fall onto the thumb, leading to pain and tenderness over the anatomical snuffbox. The radiographic appearance is different from a Colles' fracture.
* **Option B:** Smith's fracture - Also known as a reverse Colles' fracture, this occurs when the distal fragment of the radius is displaced volarly. The mechanism of injury is similar, but the radiographic appearance is reversed.
* **Option C:** Distal radioulnar joint injury - This type of injury can occur after a fall onto the wrist, but it would not result in the characteristic 'spilled teacup' sign seen in a Colles' fracture.

**Clinical Pearl / High-Yield Fact**
When evaluating a patient with a wrist injury after a fall, it's essential to consider the mechanism of injury and the radiographic appearance. A Colles' fracture is often associated with a displaced distal radius, which can be palpated as a visible step-off on the lateral X-ray.

**Correct Answer:** D.

✓ Correct Answer: B. Perilunate dislocation