A 24-year-old man sustains a fracture through the waist of the scaphoid after a fall on an outstretched hand. He is treated with cast immobilization. At 6 months, he has persistent pain and CT shows non-union with collapse of the proximal fragment. The dominant reason the proximal pole is especially vulnerable to avascular necrosis after scaphoid waist fracture is that the blood supply:

• A enters via the scapholunate ligament at the midpole and flows bidirectionally
• B is derived from the radial artery branches entering the distal pole and flows proximally in a retrograde pattern ✓
• C comes from the anterior interosseous artery entering the proximal pole directly
• D is supplied by periosteal vessels over the entire scaphoid surface uniformly

Explanation

The scaphoid receives its blood supply from branches of the radial artery (primarily the dorsal carpal branch) that enter through the distal pole and waist, flowing retrograde toward the proximal pole. A waist fracture interrupts this retrograde flow, leaving the proximal fragment ischaemic. This is why proximal pole fractures and waist fractures carry the highest risk of avascular necrosis and non-union. Option A is wrong because the supply is not bidirectional; option C is wrong because the anterior interosseous artery does not directly supply the proximal pole.

Reference: Rockwood and Green's Fractures in Adults, 9th ed.

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Written and medically reviewed by the StethoPrep medical team.