Why is the scaphoid bone most vulnerable to osteonecrosis?

The scaphoid bone's vulnerability to osteonecrosis is primarily due to its limited blood supply. This bone, located in the wrist, has an anatomical structure that makes it susceptible to interruptions in blood flow. The scaphoid receives its blood supply mainly from branches of the radial artery, with the flow entering through the distal part of the bone. This means that if the scaphoid is fractured, particularly in the middle or proximal portions, the resulting hematoma can impair the already limited vascular supply, increasing the risk of necrosis. The complication can lead to an inadequate healing process, where the bone may not regenerate adequately, leading to pain and potential joint dysfunction.

In contrast, the size of the scaphoid does not directly correlate with its risk for osteonecrosis, nor does its position in relation to the dorsal side of the wrist impact its blood supply significantly. Additionally, while the scaphoid does endure forces during wrist movements, excessive rotation is not the primary factor relating to its susceptibility to osteonecrosis. The peculiarity of its blood supply is the key reason for its increased vulnerability to this condition.