Avascular necrosis of the proximal fragment complicates fractures of the waist of the scaphoid because the main arterial supply enters the bone at which location and runs in which direction?

• A Enters the proximal pole via the volar radioscaphocapitate ligament, running proximally
• B Enters the tuberosity via the ulnar artery, running distally to proximally
• C Enters the waist directly from the anterior interosseous artery, running transversely
• D Enters the distal pole through the dorsal ridge from the radial artery, running retrograde proximally ✓

Explanation

The dominant blood supply to the scaphoid comes from the dorsal scaphoid branch of the radial artery, which enters at the dorsal ridge near the distal pole and supplies the proximal pole retrograde through the waist. A waist fracture therefore interrupts this retrograde inflow to the proximal fragment, causing nonunion and avascular necrosis. The volar supply is minor and reaches mainly the distal portion, so option A reverses the true anatomy.

Reference: Miller's Review of Orthopaedics, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.