Histologic comparison of breast implant shells with smooth, foam, and pillar microstructuring in a rat model from 1 day to 6 months.

The purpose of this study was to determine the soft-tissue response to silicone breast implants with different surface morphologies and to correlate implant microtexturing with capsular formation. Using a rat model, we inserted breast implants having three types of shells: micropillared, silicone foam, and smooth silicone (control). We used 96 adult male Sprague-Dawley rats weighing between 250 and 300 gm. Thirty-two rats were assigned to each of the three shell groups. Within each shell group, 4 rats were implanted for 24 hours, 4 for 4 weeks, 4 for 8 weeks, 4 for 12 weeks, 4 for 16 weeks, 4 for 20 weeks, and 4 for 24 weeks. The rats were sacrificed at the end of each time interval, and periprosthetic tissue was obtained for histologic analysis. Our results show a stable soft-tissue response with some macrophages and fibroblasts for the smooth silicone shell group; capsule thicknesses were 10 to 12 cells with interwoven collagen. The silicone foam prolonged the active cellular response with regard to macrophages, fibroblasts, and multinucleated giant cells, along with random collagen deposition and alternating thin and thick capsular areas. The micropillar group had a more stable cellular response, with macrophages and fibroblasts, along with disruption of the long-range orientation of collagen fibers.