Which anatomical structure is primarily assessed in the tangential projection for the carpal canal?

In the tangential projection for the carpal canal, the primary anatomical structure assessed is the pisiform bone. This technique is specifically designed to visualize the carpal tunnel and surrounding structures, where the pisiform is of particular importance because it serves as a landmark within the carpal canal. The pisiform is a small, pea-shaped bone that sits on top of the triquetrum in the wrist and is part of the carpal bones.

The tangential projection allows for the evaluation of the pisiform's position and morphology, which can be critical in diagnosing conditions such as carpal tunnel syndrome or other soft tissue pathologies that affect this area. Understanding the orientation and relationship of the pisiform to other structures in the carpal canal helps in assessing potential entrapments of the median nerve and other surrounding structures.

In contrast, while the scaphoid, lunate, and capitate are important wrist bones, they are not the primary focus of the tangential view of the carpal canal. The scaphoid and lunate are often assessed in different projections that better highlight their anatomical features, while the capitate, being centrally located in the wrist, does not specifically relate to carpal tunnel assessments in the same way the pisiform does