Os scaphoideum

Os Scaphoideum is one of the eight carpal bones in the human wrist. It is situated on the radial side of the carpus, its long axis directed from above downward, lateralward, and forward. The name "scaphoid" comes from the Greek word for "boat," due to the bone's boat-like shape.

Anatomy

The os scaphoideum is the largest bone of the proximal row of wrist bones, its long axis being from above downward, lateralward, and forward. It is approximately the size and shape of a medium-sized cashew. It articulates with five bones: the radius, the os capitatum, and three of the other carpal bones, the os trapezium, os trapezoides, and os lunatum.

Clinical Significance

Due to its position and the distribution of force in the wrist, the scaphoid is the most commonly fractured of the carpal bones, typically by a fall on an outstretched hand. This is known as a scaphoid fracture. Diagnosis can be difficult, as initial X-rays may not show any evidence of fracture. A bone scan or MRI may be necessary for definitive diagnosis.

Treatment of scaphoid fractures depends on the location of the fracture. Fractures in the proximal third of the bone have a higher risk of avascular necrosis due to the retrograde blood supply of the scaphoid. These fractures are often treated with surgery. Fractures in the distal third of the bone can often be treated with casting alone.

See Also

• Carpal bones
• Scaphoid fracture
• Wrist