Tissue reaction to prosthetic materials

Prostheses are manmade materials to replace or augment diseased or damaged body parts in a safe, reliable, economical, and physiologically acceptable manner. This chapter is restricted to materials that remain in intimate contact with blood, tissue, or body fluids for a prolonged time (weeks to years). Eyeglasses, hearing aids, wearable artificial limbs, and so on, although very important to rehabilitation, are not covered. Tissue reactions to disposable devices, such as contact lenses, or extracorporeal materials that are used briefly (dialysis equipment, etc.) are also outside the scope of this discussion. In addition, no particular distinction between blood vs tissue biocompatibility is made, as the molecular events in both are similar and assumed to be a part of the same physiological continuum. This chapter focuses on recent literature (1990 to present) that primarily deals with histopathological investigations of implants in human subjects. Because the interplay between tissues and prostheses involves various aspects of chemical, physical, and biological sciences, some basic concepts that will be useful to both the surgeon and the materials scientist are first introduced. These concepts are subsequently integrated to address the complex interplay between molecular and cellular reactions that occur when a foreign object is placed in the body.