Properties of implant alloys for artificial hip joints.

TLDR: Because the requirements demanded from implant materials for artificial hip joints are extremely high, only a very few materials are suitable for this purpose, and the inadequate material strength of hip prostheses made of the latter material is compensated for by a larger cross-section of the prosthetic stem, this depending on the geometric conditions of the femur.

Abstract: Because the requirements demanded from implant materials for artificial hip joints are extremely high, only a very few materials are suitable for this purpose. The metallic materials standardised by the ISO still predominantly include cobalt-based alloys, in cast form for wear-resistant ball heads and in forged form for fracture-resistant anchorage stems. Forged titanium-based alloys have been also used for some years for highly stressed femoral component stems. Both alloy types exhibit a higher resistance to pitting, crevice and galvanic corrosion, stress-corrosion cracking and corrosion fatigue than wrought stainless steel of relatively low strength properties. For this reason, the inadequate material strength of hip prostheses made of the latter material is compensated for by a larger cross-section of the prosthetic stem, this depending on the geometric conditions of the femur. The decision for the selection of the implant material should be made by the orthopaedic surgeon on the basis of his clinical experience, and it should not be influeced by price considerations at the expense of the quality.