Biomechanical basis for elbow hinge-distractor design.

Experimental studies of flexion-extension motion were carried out on five fresh elbow autopsy specimens to determine the average axis of rotation (AAR). The AAR is defined as the best fit single axis of rotation for the full range of flexion-extension. AAR was determined on all five elbows and found to approximate the center of the capitellum and trochlea. The motion of the elbows approximated a fixed axis, and the carrying angle defined in reference to humeral shaft and forearm axis decreased from 13 degrees to 22 degrees in extension to close to zero in full flexion. The average axis of rotation, with guidelines for its anatomic location, was used as the basis for the design and placement of a hinge-distractor in treating posttraumatic elbows with poor motion.