Any material suitable for use as a surgical implant within the body to replace or support joints or tissues. Included are such metals as aluminum, stainless steels, titanium, various forms of carbon, and especially plastics (polycarbonate, polyurethane, nylon, silicones). They have been used successfully in many areas of the body, from hip and knee replacements to mastectomies. They must be compatible with the interior environment, noncorrosive, and nondegradable, and must duplicate as closely as possible the properties of the tissues they replace. A notable breakthrough was made in this field in 1982 when a complete artificial heart was implanted successfully in a living human. Its chief component was polyurethane, the base was aluminum, and the valves were pyrolytic graphite together with polycarbonate and titanium. Other materials under consideration are styrene-butadiene copolymers for the diaphragms. The polyurethane used in the first implanted heart is “Biomer” produced by a division of Johnson & Johnson.
