[Triangular fibrocartilage complex: functional anatomy and histology].

The functional anatomy and histology of triangular fibrocartilage complex (TFCC) were investigated using 20 wrists from fresh cadavers, and a functional model of TFCC was proposed. The dynamic changes in the TFCC during pronation and supination were examined from both the proximal and distal sides. The distal side of the TFCC consisted of the disc proper (DP), the meniscus homologue (MH), the ulnolunate ligament (UL), and the ulnotriquetral ligament (UT). The prestyloid recess was observed between the DP and MH. The ulnar collateral ligament (UCL) existed at the ulnar side of the TFCC and consisted of the sheath floor of the extensor carpi ulnaris (ECU) with relatively loose ligamentous tissue recognized as 6U-portal in arthroscopy. The fan-shaped triangular ligament spreading from the fovea of the ulna was observed on the proximal side of the TFCC. It was considered to be the real radioulnar ligament connecting the radius and ulna. During pronation and supination, little deformity in the DP was observed, while the ulnar insertion of the triangular ligament was twisted. The UCL was distorted dorsally in pronation and volary in supination. In the coronal section of the TFCC, the area surrounded by the DP, MH and UCL was relatively soft and loose, and was considered to have served as a cushion during pronation and supination. From these findings, the TFCC was separated into three components; the distal component which acted like a hammock to suspend the carpus, the triangular ligament as the proximal component which stabilized the radius to the ulna, and the UCL as the ulnar component which stabilized the carpus to the ulna. We have proposed a suspension theory to account for the stability and mobility of the TFCC during pronation and supination when these three components suspend each other. The function of the TFCC can be fully accounted for by our theory.