Host Response to Orthopedic Implants (Metals and Plastics)

Biomaterials are commonly used in orthopedic surgery. The host's response to an orthopedic biomaterial encompasses the reaction to local tissue trauma, as well as the reaction to the implant itself. The acute inflammatory response to the implantation procedure involves the innate immune system, including recognition of remnants of disrupted extracellular matrix components and cellular elements by pattern recognition receptors on macrophages and other cells. The initial response stimulates a cascade of events leading to tissue reconstitution, fibrosis, or persisting chronic inflammation. The implant characteristics as well as any by-products from the implant also determine the host reaction. Precise surgical technique of implantation as well as the genotype and phenotype of the host are important determinants of implant performance. Whereas the innate immune system is always triggered with implantation of an orthopedic device, in some cases, such as with metal debris, the adaptive immune response can be activated.