Metallic Implant Materials

Metals have been used in various forms as implants. The first metal developed specifically for human use was “Sherman Vanadium Steel,” which was used to manufacture bone fracture plates and screws. Most metals used for manufacturing implants (e.g., Fe, Cr, Co, Ni, Ti, Ta, Mo, and W) can be tolerated by the body in minute amounts. Sometimes those metallic elements, in naturally occurring forms, are essential in cell functions (Fe), synthesis of a vitamin B12 (Co), and crosslinking of elastin in the aorta (Cu) but cannot be tolerated in large amounts in the body. The biocompatibility of implant metals is of considerable concern because they can corrode in the hostile body environment. The consequences of corrosion include loss of material, which will weaken the implant, and probably more important, that the corrosion products escape into tissue, resulting in undesirable effects. In this chapter we study the composition– structure–property relationship of metals and alloys used for implant fabrications.