A 22-year-old male college student falls on his outstretched hand (FOOSH) during a volleyball match. He presents with wrist pain and tenderness in the anatomical snuffbox. X-rays appear normal, but clinical suspicion for scaphoid fracture is high. Which is the most common site of scaphoid fracture?

Explanation

## Most Common Site of Scaphoid Fracture **Key Point:** The waist (middle third) of the scaphoid is the most common site of fracture, accounting for approximately 60–70% of all scaphoid fractures. ### Anatomical Distribution | Site | Frequency | Clinical Significance | |------|-----------|----------------------| | **Waist (middle third)** | 60–70% | Most common; relatively good blood supply; lower non-union risk | | Proximal pole | 20–25% | Poorest blood supply; highest non-union and AVN risk | | Distal pole | 10–15% | Best blood supply; lowest non-union risk | | Tubercle | <5% | Rare; usually avulsion injuries | ### Blood Supply Correlation **High-Yield:** The scaphoid has a retrograde blood supply entering through the waist and distal pole. The proximal pole is the last to be vascularized and is therefore most vulnerable to avascular necrosis (AVN) and non-union, especially in proximal pole fractures. **Clinical Pearl:** Although the waist is the most common fracture site, proximal pole fractures carry the worst prognosis due to tenuous blood supply and high rates of non-union (up to 12%) and AVN (up to 15%). ### Why Waist Fractures Are Most Common 1. **Biomechanics of FOOSH injury:** The force is transmitted through the radial-sided wrist, creating a shear stress at the narrowest part of the scaphoid (the waist). 2. **Anatomical vulnerability:** The waist is the thinnest and narrowest portion, making it the weakest point. 3. **Load distribution:** During wrist dorsiflexion and radial deviation (mechanism of FOOSH), maximum stress concentrates at the waist. **Mnemonic:** **WAIST = Most common; Proximal = Worst prognosis** — remember that the most frequent site is not the most problematic site.