A 25-year-old man fell on his outstretched hand and has tenderness in the anatomical snuffbox. Initial radiographs show no fracture. The surgeon warns him about avascular necrosis if a scaphoid waist fracture is present. This risk arises because:

• A The scaphoid receives its entire arterial supply proximally from the anterior interosseous artery
• B The nutrient arteries enter the distal pole and flow in a retrograde direction toward the proximal pole ✓
• C The scaphoid has a dual blood supply from both radial and ulnar arteries entering its waist equally
• D The proximal pole is covered entirely by hyaline cartilage with no vascular foramina

Explanation

The major arterial branches, derived from the radial artery, enter the scaphoid on its dorsal ridge and distal tubercle. Blood then flows retrograde from distal to proximal. A fracture through the waist or proximal third therefore interrupts inflow to the proximal fragment, predisposing it to avascular necrosis and nonunion even with adequate fixation. The claim of a dual balanced supply is false, and although much of the proximal pole surface is articular cartilage, the decisive fact is the distal entry and retrograde direction of flow.

Reference: Gray's Anatomy, 42nd ed.

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Written and medically reviewed by the StethoPrep medical team.