Force transmission through the radial head.

A technique has been developed to study the transmission of axial force across the radiohumeral joint during simulated active motion of the elbow. Variations in the line of action and in the amount of muscle load, as well as in rotation of the forearm during flexion and extension of the elbow, were assessed. Consistent patterns of force transmission were demonstrated in the three specimens that were studied. The greatest force transmission occurred between zero and 30 degrees of flexion, and it consistently decreased with increased flexion. Force transmission was consistently greater in magnitude when the forearm was in pronation than when it was in supination. The varus-valgus pivot point with the elbow extended was established to closely approximate the line of action of the brachial muscle, which crosses near the center of the lateral portion of the trochlea.