Designing Positionally Stable Smooth Breast Implants

Background: The voluntary recall and ban of several textured breast implant models worldwide, secondary to their association with Breast Implant-Associated Anaplastic Large Cell Lymphoma, has limited the key benefit of a textured surface─positional stability. We have engineered a Positionally Stable Smooth Implant (PSSI) containing millimeter-scaled cylindrical wells on the implant surface for capsule ingrowth and device stabilization. Objectives: To evaluate the long-term positional stability of PSSI designs in vivo and characterize capsule formation. Methods: Miniature breast implants were manufactured using poly(dimethylsiloxane). PSSI were designed with various dimensions of well width, depth, and number. Comparison groups consisted of smooth and textured implants. Six sterilized implants per group were implanted subcutaneously into the bilateral dorsa of Sprague-Dawley rats. Implant rotation was measured with MicroCT every 2 weeks. Implant-capsule units were explanted at 3 months for histological analysis. Results: All PSSI groups exhibited significantly less cumulative positional rotation than smooth implants (p < 0.05), with stability comparable to that of textured implants. Upon explantation, microCT and gross examination revealed notable capsule ingrowth within the PSSI wells. Histological evaluation of foreign body response showed significantly fewer pro-inflammatory M1 macrophages in the PSSI capsules compared to the textured control. Additionally, myofibroblast expression, which is implicated in capsular contracture, was significantly lower in both the PSSI and textured groups compared to smooth implants. Conclusions: This novel smooth-surface breast implant design provided equivalent positional stability and reduced pro-inflammatory M1 macrophage expression compared to textured implants. These results suggest a promising, safer alternative to textured implants for inducing positional stability.