Trapezoideum

Trapezoideum, also known as os trapezoideum or the trapezoid bone, is a small carpal bone in the distal row of the human wrist. It is one of the eight carpal bones and contributes to the complex articulation of the carpus.

Anatomically, the trapezoideum lies between the trapezium laterally and the capitate medially. It articulates proximally with the scaphoid and distally with the base of the second metacarpal. The bone is typically described as cube- or wedge-shaped, with articular surfaces that accommodate neighboring carpal bones and the second metacarpal base. Its precise facets can vary slightly among individuals.

In clinical anatomy, the trapezoideum is usually considered in the context of distal carpal row injuries. Fractures of the trapezoideum are uncommon but can occur with axial or crush injuries to the hand. They may be missed on initial wrist radiographs, so dedicated wrist imaging or CT can aid in accurate diagnosis. Management depends on fracture displacement and stability: non-displaced fractures are commonly treated with immobilization, while displaced fractures may require surgical fixation to restore carpal alignment and function.

Etymology and naming: the term trapezoideum derives from Latin, indicating a trapezoid-like shape. In some anatomical nomenclatures the bone is referred to as the trapezoid (os trapezoideum) within the distal carpal row. See also the broader group of carpal bones and their articulations.