The use of polyacrylamide gel in soft-tissue augmentation: an experimental assessment.

Background: An increasing number of soft-tissue filler substances that lack experimental and clinical data have been introduced into plastic surgery practice outside the United States. One of these substances is polyacrylamide gel. It contains 2.5% polyacrylamide and 97.5% water. It is homogenous and stable, and has optimum viscosity and elasticity. Methods: One milliliter of polyacrylamide gel was injected into the subcutaneous layer of the right ear in 28 rabbits. The rabbits were divided into two groups, according to when the material was harvested and evaluated. Material was harvested at 4 months in 15 rabbits and 7 months in 13 rabbits. Each group underwent volumetric ultrasound evaluation, magnetic resonance imaging, and histological evaluation with hematoxylin and eosin and CD68 staining. Results: Results were easily observed because of the superficial position of the injected material. There were no systemic or local complications. The samples harvested showed a clear and jelly-like consistency similar to that of the initially injected material. The volume was constant after 6 weeks, after an initial period of acute stretching. Ultrasound volumetric analysis was also constant in all groups. At 7 months, a stable volume of 1.0 ± 0.2 ml was observed. Magnetic resonance imaging scanning showed that the material was stable and that there was no inflammatory reaction. Histological analysis revealed a minimal foreignbody reaction, and the injected material was occasionally surrounded by a thin collagen membrane. The material remained in place. Conclusions: Polyacrylamide gel has a long-lasting effect, with minimal volume variation. It remains soft to the touch and in place.