Cross-linked hyaluronan (Hylan B gel): a new injectable remedy for treatment of vocal fold insufficiency--an animal study.

After injection of hylan B gel (Hylaform), the vocal folds of rabbits were studied by light microscopy at various time-points up to 12 months. Hylan B gel is a viscoelastic cross-linked and insoluble hyaluronan derivative which behaves as a soft gel. It is non-immunogenic, non-toxic and non-inflammatory and has already been used in plastic surgery for intradermal implantations. Macroscopic examination of the injected vocal folds revealed a bulging in six of the animals, but on microscopical examination the hylan B gel was encountered in all of them. Already after 1 month, and increasingly so up to 12 months, there was an ingrowth of new connective tissue, with collagen, fibroblasts and hyaluronan within the gel. No inflammatory reaction or any sign of a foreign body reaction was observed throughout the study. Hylaform may well become useful as an injection material for augmentation of vocal folds in the treatment of vocal fold insufficiency.