A 65-year-old woman falls on her outstretched hand with the wrist in dorsiflexion. X-ray shows a transverse fracture of the distal radius with dorsal displacement and angulation. Regarding the radiological features of this fracture, all of the following are characteristic EXCEPT:

Explanation

## Colles Fracture: Radiological Features **Key Point:** Colles fracture is a dorsally displaced fracture of the distal radius, classically seen in elderly patients with osteoporosis who fall on an outstretched hand (FOOSH injury). ### Classic Radiological Deformities (Lister's "Dinner Fork" Deformity) The hallmark radiological features of Colles fracture include: | Feature | Characteristic | Measurement | | --- | --- | --- | | **Dorsal angulation** | Dorsal displacement of distal fragment | >10° | | **Radial shortening** | Loss of radial height due to comminution | >2 mm | | **Radial deviation** | Lateral displacement of distal fragment | Present | | **Supination** | Rotational deformity | Common | | **Volar displacement** | Volar shift of distal fragment | **ABSENT in Colles** | **High-Yield:** The distal fragment in Colles fracture is displaced **DORSALLY**, not volarly. Volar displacement is characteristic of **Smith fracture** (reverse Colles), which occurs with a fall on flexed wrist or direct blow to dorsal forearm. ### Distinction: Colles vs Smith Fracture ```mermaid flowchart TD A[Distal Radius Fracture]:::outcome --> B{Direction of Displacement?}:::decision B -->|Dorsal displacement| C[Colles Fracture]:::action B -->|Volar displacement| D[Smith Fracture]:::action C --> E[Fall on extended wrist<br/>FOOSH injury]:::outcome D --> F[Fall on flexed wrist<br/>Direct dorsal blow]:::outcome C --> G[Dinner fork deformity<br/>on lateral X-ray]:::outcome D --> H[Garden spade deformity<br/>on lateral X-ray]:::outcome ``` **Clinical Pearl:** The mnemonic **"Colles = Dorsal"** helps distinguish: Colles fracture has dorsal angulation; Smith fracture has volar angulation (opposite direction). **Warning:** Volar displacement in a distal radius fracture should immediately raise suspicion for Smith fracture, not Colles. This is a common exam trap. ### Why This Question Tests Understanding The stem describes a classic Colles fracture (dorsiflexion injury, dorsal displacement). The correct answer is the feature that does **NOT** occur in Colles — which is **volar displacement of the distal fragment**. This is the hallmark of Smith fracture instead.