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Triangular fibrocartilage

The meaning of «triangular fibrocartilage»

The Triangular fibrocartilage complex (TFCC) is formed by the triangular fibrocartilage discus (TFC), the radioulnar ligaments (RULs) and the ulnocarpal ligaments (UCLs).

The TFC is an articular discus that lies on the pole of the distal ulna. It has a triangular shape and a biconcave body; the periphery is thicker than its center. The central portion of the TFC is thin and consists of chondroid fibrocartilage; this type of tissue is often seen in structures that can bear compressive loads. This central area is often so thin that it is translucent and in some cases it is even absent.[1] The peripheral portion of the TFC is well vascularised, while the central portion has no blood supply.

This discus is attached by thick tissue to the base of the ulnar styloid and by thinner tissue to the edge of the radius just proximal to the radiocarpal articular surface.[1]

The RUL’s are the principal stabilizers of the distal radioulnar joint (DRUJ). There are two RUL's, the palmar and dorsal radioulnar ligaments.[citation needed]

These ligaments arise from the distal radius medial border and insert on the ulna at two separate and distinct sites: the ulna styloid and the fovea (a groove that separates the ulnar styloid from the ulnar head). Each ligament consists of a superficial component and a deep component. The superficial components insert directly onto the ulna styloid. The deep components insert more lateral, into the fovea adjacent to the articular surface of the pole of the distal ulna.[citation needed]

The ligaments are composed of longitudinally oriented lamellar collagen to resist tensile loads and have a rich vascular supply to allow healing.[2][3][4]

The UCL’s consist of the ulnolunate and the ulnotriquetral ligaments. They originate from the ulnar styloid and insert into the carpal bones of the wrist: the ulnolunate ligament inserts into the lunate bone and the ulnotriquetral ligament into the triquetrum bone. These ligaments prevent dorsal migration of the distal ulna. They are more taut during supination, because in supination ulnar styloid moves away from the carpal bones volar side.[1][5]

The TFCC is important in load transmission across the ulnar aspect of the wrist. The TFC transmits and absorbs compressive forces.

The ulnar variance influences the amount of load that is transmitted through the distal ulna. The load transmission is directly proportional to this ulnar variance. In neutral ulnar variance, approximately 20 percent of the load is transmitted. With negative ulnar variance, the load across the TFC is decreased. This occurs during supination, because the radius moves distally on the ulna and creates a negative ulnar variance. With positive ulnar variance it is reversed. The load that is transmitted across the TFC is then increased. This positive ulnar variance occurs during pronation.[6]

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