An orthopedic resident is reviewing distal radius fractures in the emergency department. Among the following, what is the most common site of fracture in a typical Colles fracture?

Explanation

## Anatomical Location of Colles Fracture **Key Point:** Colles fracture occurs in the **metaphyseal region** of the distal radius, typically **2–3 cm proximal to the wrist joint line**. This is the most common and characteristic location. ### Anatomical Basis ### Why the Metaphysis? 1. **Structural weakness**: The metaphyseal region is a transition zone between the stronger diaphysis and the articular surface, making it mechanically vulnerable 2. **Cancellous bone predominance**: The metaphysis is composed primarily of cancellous bone, which is less resistant to compressive forces than cortical bone 3. **Force transmission**: During a FOOSH injury, compressive forces are concentrated in this region, leading to metaphyseal failure 4. **Age-related factors**: In elderly patients with osteoporosis, the metaphyseal bone is further weakened ### Fracture Classification by Location | Location | Fracture Type | Frequency | Notes | |----------|---------------|-----------|-------| | **Metaphyseal (2–3 cm proximal to joint)** | **Colles (typical)** | **~90%** | Most common; extraarticular | | Intra-articular (involving radiocarpal joint) | Colles variant | ~10% | Worse prognosis; requires reduction | | Radial styloid | Barton fracture (if displaced) | Rare | Often associated with dislocation | | DRUJ level | Rare | <5% | Unusual location | **High-Yield:** The **metaphyseal location 2–3 cm proximal to the wrist joint** is the defining anatomical feature of a typical Colles fracture. This distinguishes it from intra-articular variants (which have a worse prognosis) and from fractures at other sites along the distal radius. ### Clinical Significance **Clinical Pearl:** Metaphyseal Colles fractures are typically extraarticular and have a better prognosis than intra-articular fractures. However, they still require careful reduction and immobilization to prevent loss of reduction and functional impairment. ### Mnemonic: COLLES Location **C** — **C**ancellous bone region (metaphysis) **O** — **O**ccurs 2–3 cm from joint **L** — **L**ess common intra-articularly **L** — **L**ateral to medial angulation (dorsal) **E** — **E**xtraarticular (typical) **S** — **S**trong bone (cortical) is spared