Properties of biomaterials.

Metallic biomaterials, including iron-, cobalt-, and titanium-based systems, have a long history of applications for surgical implant devices. The mechanical properties of these alloys (modulus, strength, and ductility) have been used to make devices to replace skeletal structures with long-term in vivo stabilities. In addition, the passive surface oxide layers have provided chemical inertness within biologic environments. Recent trends to provide porous metallic conditions for biologic ingrowth and fixation have introduced questions with regard to the relative strength and biodegradation properties. Some biomaterial strengths have been reduced to magnitudes less than 50% of the nonporous alloys, which emphasizes the criticality of design. Surface area increases of 3-10 times has emphasized biocorrosion magnitudes, the elements released to the tissues, and the biologic consequences of these products. This article provides a brief review of these issues with emphasis on mechanical-biomechanical and chemical-biochemical properties of metallic alloys.