Effects of biostability and morphology on host response of polyurethane-based soft tissue implants

Polyurethane has been found to be one of the most successful polymers for soft tissue applications. We have investigated the effect of material biostability and morphology on the host response of polyurethane-based soft tissue implants in rabbits. The polyurethane containing allophanate linkage was prepared by using hexamethylene diisocyanate, polypropylene glycol (400) and 1,4-butane diol. Biuret-based biostable polyurethanes were prepared by using hexamethylene diisocyanate, polytetramethylene glycol and trimethylol propane and water. Samples of circular button and rectangular specimens were implanted subcutaneously in rabbits in the paravertebral region for a post-implantation period of 9 months. Relatively larger polyurethane samples with different morphology elicit a varied tissue response with our candidate polyurethane materials. A favorable tissue response was observed with rectangularly shaped thin polyurethane. Giant cell reaction, absence of fibrous tissue encapsulation and degradation were noticed for the rectangular smooth samples at the end of post-implantation period of 9 months. No malignant changes were noticed in any of these samples.