Trapezoid Bone

Key Features & Anatomical Relations

The trapezoid bone (lesser multangular bone) is one of the eight carpal bones of the hand. It’s quadrilateral-shaped and is the smallest bone of the distal row of carpal bones. It’s classified as a short bone and includes the following bony features:

- surfaces: palmar and dorsal surfaces;

- landmarks: trapezium, scaphoid, capitate, and second metacarpal articular facets.

More information regarding these bony features can be found in the Surfaces and Landmarks tabs for this bone.

The trapezoid bone is located:

- proximal to the second metacarpal bone;

- distal to the scaphoid bone;

- medial to the trapezium bone;

- lateral to the capitate bone.

It articulates with the:

- trapezium bone at the trapeziotrapezoidal joint;

- scaphoid bone at the scaphotrapezoid joint;

- capitate bone at the trapeziocapitate joint;

- second metacarpal bone, contributing to the formation of the carpometacarpal joints.

Ossification

Ossification of the trapezoid bone occurs at one ossification center, which appears within the fourth to fifth years (Standring, 2016). Complete ossification occurs during early to middle adolescence.

Variations

In some individuals:

- the trapezoid bone may be present in a bipartite condition (i.e., divided into two parts);

- an accessory bone, known the os centrale, may be present between the scaphoid, capitate and trapezoid bones (Tubbs, Shoja and Loukas, 2016).

Surface Anatomy

With regard to surface anatomy, the trapezoid bone can be palpated proximal to the base of second metacarpal bone.

List of Clinical Correlates

- Fracture of trapezoid bone (extremely rare)

References

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.

Tubbs, R. S., Shoja, M. M. and Loukas, M. (2016) Bergman's Comprehensive Encyclopedia of Human Anatomic Variation. Wiley.