Natural-Y Même polyurethane versus smooth silicone: analysis of the soft-tissue interaction from 3 days to 1 year in the rat animal model.

The polyurethane foam-covered breast prosthesis is experiencing increased clinical use. The polyurethane is felt to be responsible for altering capsule formation and reducing the contracture rate. This study characterizes the soft-tissue response to the Natural-Y Même polyurethane foam versus smooth silicone in a rat model. Implants were fashioned from an unbacked polyurethane foam specimen used to cover the Natural-Y prosthesis, a silicone shell covered with the Natural-Y foam, and a smooth silicone control. Materials were placed subcutaneously into the backs of male Lew/SsN rats (n = 81) for 3, 7, 14, and 28 days and 3, 6, and 12 months. Implants were then harvested with their soft-tissue response and evaluated histologically. Analysis demonstrates that microstructuring of a surface, as opposed to a smooth material, will dramatically alter the early, intermediate, and late wound-healing events. The soft-tissue response was observed to be dependent on implant site, material chemistry, and morphology as characterized by exudate formation, macrophage invasion, multinucleated giant cell formation, collagen deposition, foam degradation, and angiogenesis.