Biomaterials for Total Joint Replacements

The European Society for Biomaterials defines a biomaterial as “a material that interacts with the biological systems to evaluate, treat, reinforce, or replace a tissue, organ, or function of the organism” and the biocompatibility as “the ability of a material to perform with an appropriate host response in a specific application” [1]. Biocompatibility of a biomaterial is tested by in vitro screening, in vivo testing, and clinical monitoring; each step evaluates the biological response in different conditions. In vivo, a few seconds after the implantation, the biomaterial is rapidly adsorbed by proteins, whose quantity and organization depend on the characteristics of the biomaterial, such as chemical composition of the bulk and surface, surface geometry, chemical and physical properties, and the properties of the proteins [2]. The host cells contact the protein layer [3]; in total joint replacements, bone cells growing on the prosthetic surface determine an “osseointegration” [4], fibrous cells a “fibrous fixation”.