Biomechanical test and research are conducted mainly on third and fourth generation of bone models because of high stability of parameters and better validated of artificial bone in comparisons with cadaver. That kind of bone is produced with inner porous foamed material with composite fiber glass reinforced epoxy resin outher cortical layer overly polyurethane material.  Earlier models of bone (for example second generation) have not hollow intramedullary canal at the center of the rigid polyurethane foam core.