The triangular fibrocartilage complex: an important component of the pulley for the ulnar wrist extensor

The extensor carpi ulnaris (ECU) tendon is the only wrist motor tendon that broadly connects with the triangular fibrocartilage complex (TFCC) of the wrist. The goal of this study was to determine the biomechanical effect of the TFCC on the function of the ECU. The effect of avulsion of the TFCC on the changes in mechanics of the ulnar wrist extensor tendon was investigated in 8 fresh-frozen cadaver forearms. Excursion of the ECU tendon was continuously recorded over the functional range of wrist extension and ulnar deviation in intact wrists, wrists with ulnar styloid fractures, wrists with TFCC release from the distal ulna, and after excising the distal ECU tendon sheath. The ECU tendon demonstrated a 30% increase in excursion during wrist extension after release of the TFCC from its attachment on the distal ulna. During 60 degrees of wrist extension, excursion of the ECU tendon was 4.8+/-1.9 mm in the intact wrists and 6.3+/-2.0 mm after TFCC release. This change in excursion represented 1.4 mm of bowstringing for the ECU tendon during 60 degrees of wrist extension. Further incision of the distal part of the extensor sheath produced only 6% increase in excursion of the ECU. Results of this study suggest that the TFCC is an important component of the pulley for the ulnar wrist extensor. These findings imply that disturbance of the wrist extensor after TFCC injury may potentially contribute to abnormal loading and force transmission through the ulnar wrist and the TFCC, and support the growing consensus that integrity of the TFCC should be restored in the presence of TFCC injuries.