Effects of local instillation of triamcinolone on the capsules around silicone bag-gel prostheses in animals.

"Soft" silicone bag-gel miniprostheses were implanted in 103 rats. The experimental animals had periprosthetic instillations of zero, 0.2, or 2 mg of triamcinolone acetonide at implantation. The compressibility, the architecture, and the chemical composition of the surrounding tissues were observed at 10 and at 120 days. The compressibility was also measured by mechanical means at 10 day intervals. At 120 days all capsules were similar. All the capsules gradually became firmer with time after the implantation. After 60 days, the steroid-treated capsules were very slightly more compressible (softer) than the controls. This slight difference in compressibility could not be correlated with the other changes in the capsule properties we examined. It is suggested that the structure of these capsules may be similar to that of immature scar, and that it is kept in this condition by the continued stimulus of the foreign implant.