Displaced intra-articular fractures of the distal radius: the effect of fracture displacement on contact stresses in a cadaver model.

Contact stresses in the wrist were measured after simulating displaced fractures of the lunate fossa in the distal radius of eight human cadaver arms. Osteotomies created displaced lunate fossa fractures of 0, 1, 2, and 3 mm. Contact stresses were measured with Fuji pressure-sensitive film after loads of 100 N were applied to the wrist through wrist flexor and extensor tendons. Mean contact stresses were significantly increased with step-offs of 1 mm or more. Maximum stresses and overloaded areas were significantly increased with step-offs of 2 mm or more. As the magnitude of the fracture displacement increased, there was a shift in the focus of the maximum stresses toward the fracture line. In this model, simulated displaced die-punch fractures created alterations in both the magnitude and location of contact stresses in the wrist joint.