The effect of a bacterial contamination on the formation of capsular contracture with polyurethane breast implants in comparison with textured silicone implants: an animal study.

[INTRODUCTION] One of the most common complications following breast augmentation is capsular contracture. The subclinical infection of the implant is often considered to be one of the main risk factors. It is believed that polyurethane (PU) implants, because of their larger foam-like surface, have lower capsular contracture rates due to better tissue integration. It remains unclear if bacterial contamination and biofilm formation result in higher capsular contracture rates under the condition of the increased surface of PU implants compared to textured silicone-gel implants. The effect of this bacterial contamination was examined in an animal-based study.

[METHODS] A total of 80 mini implants (40 textured silicone-gel implants and 40 PU implants) were implanted in the dorsum of female Wistar rats. In each group, 20 implants were inoculated before implantation with a standard amount of Staphylococcus epidermidis. Capsules and implants were explanted after 60 days, followed by double-blind histological, immunohistochemical, and microbiological examinations.

[RESULTS] Macroscopic separation of the total capsule in the textured implant group was possible whereas the growth of surrounding tissue into the foam structure of PU implants made separation in that group difficult. After contamination, a thicker capsule could be observed in both groups without significant differences. Histologically, capsules around PU implants showed significantly lower expression of parallel myofibrils. We were able to describe a significant higher infiltration with inflammatory cells in capsules around PU implants both with and without contamination. Microbiological investigations revealed positive growth of S. epidermidis around one PU implant without related signs of capsular contracture.

[DISCUSSION] This study demonstrates that aside from the surface of silicone implants, bacterial contamination has major impact on the architecture of capsule formation. In our study, we were able to demonstrate that bacterial contamination leads to a thicker capsule and an increased tissue reaction with a higher amount of inflammatory cells. However, a resulting bacterial infection was only demonstrated in one case and had an insignificant influence on capsule architecture. The observed inflammatory reaction around PU implants was observed as a nonbacterial, granulomatose foreign body reaction.

[EBM RATING] Level I: Evidence obtained from at least one properly designed randomized controlled trial.