Biomechanical Effect of Triquetral and Scaphoid Excision on Simulated Midcarpal Arthrodesis in Cadavers

PurposeTo 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.MethodsTen 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.ResultsCompared 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).ConclusionsWhen performing 4-corner arthrodesis, scaphoid and triquetrum excision may improve motion at the cost of increased mean radiolunate contact pressure.