Material properties of breast periprosthetic capsule

The most frequent complication occurring after implanting silicone breast prostheses is the contracture of the fibrous capsule (FCC) that commonly forms within the first few months after surgery (Gylbert et al., 1990). Capsule formation around foreign materials that constitute any implanted medical device is a normal wound healing process whose aim is to isolate the implanted device from the surrounding tissue. When viewed under a microscope, the fibrous capsule surrounding a breast implant is composed of bundles of collagen fibers interspersed with nuclei of fibroblasts, small blood vessels and macrophages and embedded in a water-saccharides ground substance. However, in some instances the capsule contracts around the implant, thus producing increase of hydrostatic pressure at the implant site, due to the scarce compressibility of the silicone prosthesis; the breast implant is forced into a spherical shape and the breast turns out to become firm and in severe cases painful and distorted (Biggs et al., 1990). FCC can develop unilaterally or bilaterally and its development is multifactorial including nonspecific and specific foreign body reaction, periprosthetic infection, hematoma, effect of mechanical stresses and others (Asplund et al., 1996). The severity of the contracture is commonly classified by physicians according to the Baker scale, ranging from degree I (absence of contracture) to degree IV (severe and painful contracture, the prosthesis needs to be removed); attempts to quantitatively define capsular contracture have not been fruitful yet. In the present study, a mechanical characterization of capsular samples was attempted in order to investigate a correlation between the degree of capsular contracture and some mechanical properties of the tissue. Such correlation can provide better understanding of the contracture process.