## Scaphoid Blood Supply and Zones **Key Point:** The scaphoid has a retrograde blood supply that enters through the distal and middle thirds, making the proximal pole the most vulnerable zone. ### Anatomical Zones | Zone | Blood Supply | Complication Risk | |------|--------------|-------------------| | **Proximal pole** | Retrograde only; terminal branches | Highest risk of AVN and nonunion | | **Waist** | Mixed retrograde and distal | Moderate risk | | **Distal pole** | Robust anterograde supply | Lowest risk | | **Tubercle** | Direct branches | Good healing potential | ### Pathophysiology 1. The scaphoid lacks a nutrient artery 2. Blood supply is entirely from periosteal vessels entering through the distal and middle thirds 3. The proximal pole receives only terminal branches of these vessels 4. Fractures at the waist or proximal pole disrupt this tenuous retrograde flow 5. Prolonged immobilization and nonunion are common sequelae **High-Yield:** Proximal pole fractures have a 10–12% nonunion rate and up to 50% risk of AVN if untreated, compared to <5% for distal fractures. **Clinical Pearl:** Nonunion of the proximal pole may require vascularized bone graft (e.g., medial femoral condyle graft) rather than standard ORIF. 
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