Ulnopisiform ligament

The ulnopisiform ligament is a component of the palmar ulnocarpal ligament complex of the wrist.

Origin and course: It is one of the fascicles making up the palmar ulnocarpal ligament, alongside the ulnocapitate, ulnolunate, and ulnotriquetral ligaments. Its fibers fan out from the styloid process of the distal ulna to the palmar surfaces of the triquetrum, lunate, capitate, and pisiform carpal bones.

Structure The palmar ulnocarpal ligament is a strong, fibrous structure composed of multiple bundles of fibers, including the ulnocapitate, ulnolunate, ulnotriquetral, and ulnopisiform ligaments, and the fibers of these ligaments are often confluent and indistinguishable from each other, as described by Moritomo (2013).

Function The palmar ulnocarpal ligaments strengthen the articular capsule of the radiocarpal joint and prevent displacement of the head of the ulna.

In a more recent, distinct description, a separate cadaveric study takes a different view, proposing the ligament as a discrete anatomical structure rather than just a bundle within the palmar ulnocarpal complex: although the ulnar collateral and ulnocarpal ligaments of the wrist are well described, a distinct ligamentous connection between the distal ulna and the pisiform had not been consistently recognized, and this study aimed to describe the ulnopisiform ligament and define its anatomical relationships with the ulnocarpal complex and the pisotriquetral joint. In all eight dissected cadaveric wrists, a capsuloligamentous structure was consistently identified extending from the ulnar head and adjacent portion of the ulnar styloid to the proximal ulnar surface of the pisiform, forming part of the capsuloligamentous boundary of the pisotriquetral joint. The authors also found a distinct fibrous connection linking the pisiform to the ECU subsheath, establishing an indirect anatomical link to the TFCC. uninsubriauninsubria

So there's a notable terminological tension worth flagging for editorial purposes: classic literature treats it as a mere fascicle of the palmar ulnocarpal ligament (like in Terminologia Anatomica 2), while this newer cadaveric study argues it deserves recognition as its own distinct ligament with a specific role in pisotriquetral joint stability.