Clinical and histologic evaluation of a new injectable implant: hydrophilic polyacrylamide gel.

Hydrophilic polyacrylamide gel is a new, jellylike transparent implant that consists of 95% water and 5% polyacrylamide, and it has been applied in many countries for many years as a sort of injectable implant. However, there are no data regarding human tissue reaction to hydrophilic polyacrylamide gel to date. Thirty-one patients who had undergone the injection of hydrophilic polyacrylamide gel for soft-tissue augmentation from September 1998 to November 2001 wanted to remove the implant. Hematoxylin-eosin-stained sections from each cyst of tissue sample were investigated and analyzed with light microscopy. The tissue slices of 12 patients who had received an injection of silicone from 1988 to 1994 were reviewed. The difference in histologic features was assessed. The inflammatory reaction of hydrophilic polyacrylamide gel was characterized by the presence of more foreign body giant cells. The cellular response ranged from moderate or marked (4 to 18 months) to mild (>18 months). The difference was statistically significant (P <0.05). Little lymphocyte infiltration was shown in all slices of hydrophilic polyacrylamide gel. There were clusters or diffuse lymphocyte infiltration on histologic observation of the liquid silicone. The difference was significant (P <0.001). In summary, hydrophilic polyacrylamide gel may evoke a human tissue inflammatory response similar to other foreign materials. Lumpy subcutaneous nodules, mastodynia, and difficult removal may limit its application in breast augmentation.