Anatomically, the scaphoid may be divided into proximal, middle (termed the waist), and distal thirds. Most of the blood supply to the scaphoid enters distally. The proximal part of the scaphoid has no blood vessels entering it, depending instead on vessels that pierce the midportion. Fractures of the proximal third of the scaphoid account for 20% of scaphoid fractures, those of the middle portion account for 60%, and fractures of the distal part make up the remaining 20%. Diminished blood flow to the proximal pole is noted in about one third of fractures at the waist level. This reduced blood supply may result in avascular necrosis of the proximal pole of the scaphoid. Almost 100% of proximal pole fractures result in aseptic necrosis. Displaced scaphoid fractures have a nonunion rate of 55-90%.
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