Histological evaluation of pore size and shape in silicone implants in rhesus monkeys

Silastic has been used with varying success as an implant material. When Silastic implants fail, migration and infection are generally involved. Perforation of the implant has been suggested as a means of minimizing implant migration. In this study, 30 implants were studied in Rhesus monkeys. The implants varied in external geometric form and in perforation size. Results indicated that fibrous encapsulation of the implant occurred within two weeks. The tissue readily invaded the perforations regardless of pore size. The configuration of connective tissue was unaffected by external geometry. Perforated implants were less mobile than non-perforated implants, and implants with perforations of 3 mm or more contained dense fibrous connective tissue supported by an underlying vascular mesenchymal tissue not seen in implants with smaller pores. As a result of this study, we recommend that perforations be used in Silastic implants and that these perforations be at least 3 mm in diameter.