Distribution of pressures and forces on the wrist after simulated intercarpal fusion and Kienböck's disease.

Limited intercarpal fusion has been recommended for the treatment of Kienböck's disease. The effects of a simulated scapho-trapezio-trapezoid (STT) fusion and simulated Kienböck's disease on the biomechanics of the radio-ulno-carpal joint were investigated. The percent force, the centroid of the force, and the percent contact area in each fossa were determined. It was found that a STT fusion with the scaphoid in a neutral or extended position unloads the lunate fossa. STT fusion in flexion does not affect lunate load. It is concluded from this biomechanical experiment that STT fusion with the scaphoid in a neutral or extended position unloads the radiolunate joint regardless of the condition of the lunate. This load is shifted to the radioscaphoid articulation.