Study of encapsulation of silicone rubber implants in animals. A foreign-body reaction.

It has long been known that the formation of a fibrous capsule around an implant is a general phenomenon in nature, an inevitable result of the tissue defense mechanism called the foreign body reaction. We have investigated this reaction in animals and find it consists of a series of interrelated processes in which the final result may vary, depending on the susceptibility of the foreign material to phagocytosis, incorporation by giant cells, or isolation by fibrosis. This susceptibility depends, in turn, on the physical and chemical properties of the implant. The process of capsule formation, as well as the structure of the final capsule, is similar in animal models and in humans--so that investigations of human encapsulation may be done in animals. The cause of abnormal induration around human breast implants is still unknown, and the question of whether normal induration in the animal model can be used to elucidate abnormal clinical induration depends on further investigation of both phenomena.