The effect of a simulated scaphoid malunion on wrist motion.

A scaphoid malunion results when a scaphoid fracture heals in a flexed position or when a scaphoid nonunion with carpal collapse is grafted without correction of the angular deformity. The effects of scaphoid malunion on wrist motion were simulated in a cadaveric study. It was found that the loss of wrist extension is proportional to the angular deformity. Loss of radiocarpal extension occurred at 15 degrees of angulation and loss of midcarpal extension occurred at 30 degrees of angulation.