Trapezoid bone fracture.

Fractures of the carpal bones involve only a single bone or complex bones with or without ligament rupture. However, fractures of the trapezoid are rarely seen. Because the trapezoid is fastened to the trapezium, capitate, and scaphoid by strong ligaments, fracture or dislocation is limited by this rigid fixation. The authors present a single bone fracture of the trapezoid in a 40-year-old man. A tomogram of the carpal bone was useful in diagnosing the trapezoid fracture. The mechanism for development of fracture of the trapezoid alone is unknown. However, fracture of the trapezoid seemed to occur when the wrist joint was forced with excessive flexion stress that was placed on the trapezoid through the second metacarpal bone indirectly. This occurred in the same manner that a walnut is broken with nutcrackers.