Abstract: A method of making a joint implant prosthesis which has a shaft adapted to fit into the bone cavity of a tubular bone and having a core region and a shaft region. The geometry of the bone cavity is determined by an irradiation method and based upon the detected geometry, the shaft is dimensioned. First a geometric centroid axis of the bone passage is determined and then the core region built up by computer around this axis with the aid of finite element analysis based upon geometry of the bone cavity. The boundary conditions of an undercut-free shaft and uniform distribution of the normal stresses in the shaft bone transition region are observed. The second boundary condition is also used as a control in the coating of the core with synthetic bone material and in the configuration of the surface region.

Abstract: A forged piston blank for a forged piston of an internal combustion engine is formed with undercuts between the eye portions and crown side or head portions of the ears so that a larger piston pin may be accommodated by virtue of the fact that the wall thickness at the upper portion of the eye is greater than the wall thickness of the head portion of the ear.