A 24-year-old man sustains a fall on an outstretched hand and is diagnosed with a displaced fracture through the waist of the scaphoid. He is counselled about the high risk of avascular necrosis of the proximal fragment. The anatomical basis for this complication is:

• A Blood supply enters the distal pole and flows in a retrograde direction to the proximal pole ✓
• B The entire scaphoid is supplied by branches of the anterior interosseous artery entering the tubercle
• C The proximal pole is supplied by branches of the ulnar artery through the radioscapholunate ligament
• D Nutrient arteries enter only the proximal pole and are disrupted by distal fractures

Explanation

The scaphoid receives its arterial supply from the dorsal scaphoid branches of the radial artery, which enter along the dorsal ridge at the distal half, and from branches entering the tubercle. Flow is therefore retrograde: distal to proximal. B waist fracture disrupts this retrograde inflow, devascularising the proximal fragment. Option D reverses the entry points, and the ulnar artery contributes nothing to scaphoid supply.

Reference: Campbell's Operative Orthopaedics, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.