The lunotriquetral joint: kinematic effects of sequential ligament sectioning, ligament repair, and arthrodesis.

This experiment was conducted to study the effects of sequential sectioning of the ligaments of the lunotriquetral (LT) joint and the effects of simulated repair or arthodesis on kinematics of the wrist joint using an x-ray stereophotogrammetric technique. A 3-dimensional coordinate software program calculated relative motion between bodies as screw axis displacement and rotation about each axis. Sectioning of the proximal and dorsal component of the LT ligament had little effect on carpal kinematics, but sectioning of the proximal and palmar components of the ligament resulted in flexion of both the lunate and triquetrum, producing a volar intercalated segment instability (VISI) pattern. The triquetrum supinated away from the lunate after sectioning of the entire LT ligament. Greater VISI occurred after sectioning the dorsal radiotriquetral and scaphotriquetral ligaments. Progressive destabilization of the LT joint results in increasing kinematic alterations; however, these may not exactly mimic the clinical situation. Moving the wrist through 1,000 cycles increased the instability. Dorsal repair of the LT ligament realigned the lunate and triquetrum, and LT fusion corrected triquetral supination. The latter, however, resulted in overcorrection into extension, which prevented a full wrist extension. The repair used may be insufficient to restore the palmar ligamentous integrity. Lunotriquetral arthodesis was difficult to simulate, providing some insight into the cause of clinical nonunions. Severe VISI is not correctable by repair or arthrodesis and requires further study using reconstructive procedures not discussed here.