Biomechanical effect of triquetral and scaphoid excision on simulated midcarpal arthrodesis in cadavers.

ABSTRACT

PURPOSE: To examine the biomechanical effects of triquetral and scaphoid excision on wrist motion and radiolunate contact characteristics in a cadaveric model after simulated 4-corner arthrodesis with rigid internal fixation. METHODS: Ten fresh-frozen cadaveric upper extremities were studied. For all surgical manipulations, the motion was measured and contact characteristics were assessed using ultralow prescale pressure-sensitive film. RESULTS: Compared with the intact specimen, simple 4-corner arthrodesis with scaphoid retention led to a significant decrease in flexion (-23%), extension (-69%), radial deviation (-129%), and ulnar deviation (-25%), but no significant change in radiolunate contact characteristics. After 4-corner arthrodesis with scaphoid excision, there was a significant increase in radial deviation (+213%) without significant change in radiolunate contact characteristics, but average radial deviation was still less than in the intact specimen. After further excision of the triquetrum, radial deviation increased significantly (+238%), to a mean value 5% greater than that of the intact state, but at the cost of a significant increase in mean radiolunate contact pressure (+44% compared to the intact state). CONCLUSIONS: When performing 4-corner arthrodesis, scaphoid and triquetrum excision may improve motion at the cost of increased mean radiolunate contact pressure.