An articular surface prosthesis composed of a porous material that is substantially noncorrodible and nonbiodegradible by body fluids. The prosthesis serves as a replacement of, for example, a femoral cap. The prosthesis fits over the femur which is shaped, typically, to a right circular cylinder outline,...http://www.google.de/patents/US4911720?utm_source=gb-gplus-sharePatent US4911720 - Particular surface replacement prosthesis
