## Distinguishing Colles from Smith Fracture ### Mechanism and Direction of Displacement **Key Point:** The defining difference between Colles and Smith fractures lies in the direction of displacement of the distal fragment — dorsal in Colles, volar in Smith. ### Comparison Table | Feature | Colles Fracture | Smith Fracture | |---------|-----------------|----------------| | **Mechanism** | Fall on extended wrist (FOOSH) | Fall on flexed wrist; direct blow | | **Distal fragment displacement** | **Dorsal** (posterior) | **Volar** (anterior) | | **Distal fragment angulation** | Dorsal angulation | Volar angulation | | **Classic deformity** | "Dinner fork" (dorsal prominence) | "Reverse dinner fork" (volar prominence) | | **Frequency** | ~90% of distal radius fractures | ~5–10% of distal radius fractures | | **Age group** | Elderly (osteoporotic bone) | Younger patients; direct trauma | ### Clinical Pearl **High-Yield:** The **dorsal displacement** of the distal fragment in Colles fracture creates the characteristic "dinner fork" deformity when viewed from the lateral side — this is the single most reliable radiological discriminator. In contrast, Smith fracture shows volar (anterior) displacement, creating a "reverse dinner fork" appearance. ### Mnemonic **COLLES = Dorsal (backward)** — think "**C**olles goes **C**ephalad (dorsally)" **SMITH = Volar (forward)** — think "**S**mith slides **S**tay-forward (volarly)" ### Why Other Features Are Not Discriminating - **Radial styloid involvement:** Can occur in both Colles and Smith fractures; not specific to either. - **Ulnar styloid fracture:** Present in ~50% of both Colles and Smith fractures; not a discriminator. - **Volar displacement:** This is the defining feature of Smith, not Colles — the opposite of the correct answer. [cite:Rockwood and Green's Fractures in Adults 9e Ch 18] 
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