US Patent 4,229,841
United States Patent and Trademark Office
University of Iowa Research Foundation (Iowa City, IA, US)
A proximal component affixed to the radius of the forearm and a distal component affixed to the hand are connected by a joint which prevents axial rotation between the components relative to the forearm axis and provides relative movement of the components about two substantially perpendicular axes which are transverse to the forearm axis for radial-ulnar hand movement and flexion-extension hand movement.
Youm, Youngil and Flatt, Adrian E. Wrist prosthesis. US Patent 4,229,841 filed November 17, 1978 and issued October 28, 1980. https://ir.uiowa.edu/patents/21