Trapezoid Bone

The structure indicated is the trapezoid bone of the hand.

There are three groups of bones in the hand:

1. Carpal bones (8 in total)
2. Metacarpal bones
3. Phalanges

The carpal bones are separated into two rows:

1. Proximal row
2. Distal row

The trapezoid bone is located in the distal row of carpal bones. There are four bones in the distal row:

1. Trapezium
2. Trapezoid
3. Capitate
4. Hamate

It’s easy to confuse the location of the trapezoid with the adjacent and similarly named trapezium bone. A way to remember where the trapezium is located is that trapezi-UM rhymes with thUMB, and therefore articulates with the 1^st metacarpal of the thumb, the trapezoid bone lies just medial to it.

Learn more about the bones of the hand in this anatomy tutorial.