THE CAPSULE QUALITY OF SALINE-FILLED SMOOTH SILICONE, TEXTURED SILICONE, AND POLYURETHANE IMPLANTS IN RABBITS - A LONG-TERM STUDY

Recently, there have been many new designs in both the surface texture and chemical composition of breast implants that claim reduced constrictive capsular formation. The purpose of this study was to utilize a quantitative method to determine the firmness of capsules formed around saline-filled smooth silicone, textured silicone, and polyurethane implants in an experimental rabbit model 1 year after implantation Our objective was to analyze the histologic, biologic, and biochemical content of the respective capsules to account for any differences in physical behavior. Forty-five smooth silicone, textured silicone, and polyurethane implants were placed in one of three positions beneath the panniculus carnosus muscle of New Zealand White rabbits. After 1 year, all capsules were palpated and classified according to firmness. Intracapsular static and dynamic pressure measurements were obtained by placing a pressure monitor (Stryker) in an injector port attached to the individual implants. Capsular firmness was significantly greater in the textured silicone implants than in the smooth silicone or polyurethane implants after 1 year. The dynamic qualities of the periprosthetic soft tissues were measured while saline was injected into the implants. The capsules around the textured silicone implants generated significantly higher pressures than the smooth silicone or polyurethane counterparts. The capsules around the polyurethane implants were the softest and most compliant in all categories. Histologically, there is a significant inflammatory response surrounding the textured silicone implants that does not exist in the capsules around the smooth silicone implants. The capsules around the polyurethane implants have the least fibrous tissue deposition. There is a decrease in the proportion of type III collagen in the capsules around the textured silicone implants versus smooth silicone or polyurethane implants. The in vitro contraction patterns of the fibroblast-populated collagen lattices do not reveal the contraction differences observed in vivo in rabbits. However, there are many components that determine contractility. This area deserves further investigation.