Regenerative Tissue Matrix Protects against Radiation-Induced Capsular Contracture in a New in-Vivo Model of Silicone Implant Breast Reconstruction

Introduction: Capsular contracture of mammary implants is a problem for which definitive solutions remain elusive. The aim of this study was to assess the effect of radiotherapy on encapsulation of AlloDerm®-wrapped textured silicone implants to test the hypothesis that interposition of a biological barrier between the implant and tissue pocket may protect against capsule formation and severity of contracture.

Materials and Methods: Twenty Wistar Albino rats were used. 1.5x1cm textured silicone implant shells were inserted into subcutaneous pockets in the thoracodorsal areas with (n=10) or without (n=10) AlloDerm®-wrapping [Lifecell Corp., Branchburg, New Jersey, USA]. Single dose 18Gy radiation was given with a low energy X-ray orthovoltage machine. Implants were explanted after 12 weeks and examined macroscopically and histopathologically. Specimens were compared in terms of adhesions to surrounding tissues, capsule thicknesses, structural properties and with quantitative analysis of cell counts for myofibroblasts, fibroblasts and inflammatory cells.

Results: Capsules in the experiment group were thinner and less cellular in terms of fibroblasts and myofibroblasts compared with the control group including: a very statistically significant (p<0.01) decrease in both the mean capsule thickness and the myofibroblast and fibroblast counts. Actual mean capsule thicknesses were 40µm (range 32-59µm) in the control group and 20.8µm (range 14-27µm) in the Alloderm group. Mean myofibroblast and fibroblast counts were 98,320 in the controls and 57,700 in the Alloderm group. The inflammatory cell infiltrate was also less in the Alloderm group, but of borderline statistical significance (p=0.057).

Conclusion: We describe a new model of radiotherapy induced capsular contracture. We demonstrate for the first time a statistically significant protective effect of Alloderm interposition on radiotherapy-induced capsule formation with textured silicone implants. This animal model is a starting point in the investigation of the complex tissue-implant interactions in irradiated implants. There is sufficient weight of evidence to justify further studies with Alloderm interposition in patients with this commonly used product, starting with the small subpopulation for whom implant reconstruction has been chosen despite the need for radiotherapy or in whom future radiotherapy may be a possibility.