To improve wear resistance by forming a prosthesis support element having a support surface to be used in a prosthesis implant out of a superhigh polymer polyethylene with multiaxial molecule orientation having a specified molecular weight.

A shank tray has a base part 1 and the base part 1 has a lip 3 risihg on the perimeter 2 thereof and a spigot 4 which extends downward from the base 1 and is allowed to be mounted on a bone to be inserted. A support element 5 has recesses 6 which are formed spaced at an interval to receive a joint cone of a thigh implant and is supported on the base part 1. The support element 5 is formed out of superhigh polymer polyethylene with multiaxial molecule orientation exceeding 1,000,000 in molecular weight. In this process, one direction of the multiaxial molecule orientation is extended parallel with the length of a support surface or extended along the length of the support surface. One direction of the multiaxial molecule orientation is extended parallel with the width of the support surface or in a way crossing the width of the support surface.