Bone · Hand

Scaphoid

Os scaphoideum

The boat-shaped bone on the thumb side of the wrist, and the only carpal that lies across both rows — it is set obliquely, so its upper half sits in the proximal row against the radius while its lower half meets the trapezium and trapezoid in the distal row. Its tubercle is the firm bump at the thumb-side heel of the hand, and its waist forms the floor of the anatomical snuffbox, the hollow that appears between the thumb tendons when the thumb is lifted. Its blood supply is unusual and is plain anatomy worth knowing: the vessels enter near the far end of the bone and run backwards through it, so the near half is fed second-hand. Because it spans both rows, it is the strut through which the two halves of the wrist are mechanically tied together.