The Concept of Biocompatibility

Biocompatibility is a condition met by a biomaterial/device, based on the criteria used to assess the acceptability of the tissue response in relation to the required function of the device. Determinants of the tissue response reside in the intrinsic wound-healing process in the particular tissue or organ into which the biomaterial has been implanted. The response to a biomaterial is, therefore, a characteristic of the host tissue's wound-healing process as well as being a characteristic of the biomaterial. The macrophage plays a critical role in the tissue response to implants. It first appears during the inflammatory process induced by the surgical trauma of implantation, and is attracted to the hypoxic environment related to the dead space associated with the presence of the implant. Macrophages and fibroblasts adjacent to an implant form a synovium-like tissue that represents a chronic inflammatory response. Recent studies have demonstrated the presence of α-smooth muscle actin-expressing cells capable of contraction, and lubricin, a lubricating glycoprotein, in the tissue around loose implants. These findings may explain the persistence of fibrous scar-like tissue around failing prostheses.