Due to their superior electrical and thermal conductivity and mechanical properties, metals are used as biomaterials. Some metals are used as an alternative to hard tissue replacement, such as total hip and knee joints. Some metal alloys are used for active roles in devices such as vascular stents, catheter guide wires and cochlear implants. “Vanadium steel” used as a base metallic alloy for human use for bone fracture plates and screws. Most metals (eg Fe, Cr, Co, Ni, Ti, Nb and Mo) are used for alloys used to make implants, which can only be accepted by the body in small quantities.