Why are scaphoid fractures prone to nonunion or avascular necrosis (AVN)?

Study for the NBCOT Hand Injuries and Intervention Test. Prepare with flashcards and multiple choice questions, each question offers hints and explanations. Get ready for success!

Multiple Choice

Why are scaphoid fractures prone to nonunion or avascular necrosis (AVN)?

The key idea is that the scaphoid’s blood supply is retrograde—the vessels mainly enter distally and travel toward the proximal pole. A fracture, especially in the waist or through the proximal part, can disrupt those vessels and cut off blood flow to the proximal fragment. Because the proximal pole receives relatively little direct blood supply, it can become avascular and fail to heal, leading to nonunion and avascular necrosis. The other statements misstate the vascular pattern: the scaphoid isn’t well supplied in a way that protects the proximal pole, its blood supply isn’t predominantly from the ulna, and AVN is indeed related to where the fracture disrupts the blood flow.

The key idea is that the scaphoid’s blood supply is retrograde—the vessels mainly enter distally and travel toward the proximal pole. A fracture, especially in the waist or through the proximal part, can disrupt those vessels and cut off blood flow to the proximal fragment. Because the proximal pole receives relatively little direct blood supply, it can become avascular and fail to heal, leading to nonunion and avascular necrosis. The other statements misstate the vascular pattern: the scaphoid isn’t well supplied in a way that protects the proximal pole, its blood supply isn’t predominantly from the ulna, and AVN is indeed related to where the fracture disrupts the blood flow.

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