Collagen coatings reduce the incidence of capsule contracture around soft silicone rubber implants in animals

Silicone rubber miniprostheses known to be associated with a high rate of experimental capsule contracture were implanted subcutaneously in rats. Prostheses were coated either with 2 layers of collagen cross-linked with formaldehyde or with 1 layer of collagen cross-linked with glutaraldehyde. Noncoated prostheses were implanted as controls. Contracture was defined as grossly observable distortion of the implant mounds from round to avoid. Capsules were examined histologically at explant at 255 days. In the control group with no coating present capsules formed very early in 100% of the implants. The group with a 2-layer, formaldehyde-treated collagen coat demonstrated the greatest total surface area covered with coating, the least degree of capsule formation, the lowest rate of contracture (7%), and the longest onset. The group with a single layer of collagen treated with glutaraldehyde showed an intermediate coverage of coating, an intermediate degree of capsule formation, an intermediate contracture rate (50%), and an intermediate time of onset. These observations confirm earlier results by showing a correlation between intact collagen coating and absence of capsule formation, and also further demonstrate a significant reduction in the rate of capsule contracture for collagen-coated implants.