LONG-TERM BIOSTABILITY OF POLYACETAL (DELRIN(R)) IMPLANTS

Over the past two decades, polyacetal homopolymer (Delrin(R)) has been used for heart valve occluders and in total hip replacements. Both ty pes of implants are subject to mechanical loads that induce wear, and excessive wear could adversely affect the performance of the device. T he present study examined components of Delrin heart valves and hip pr ostheses that had been recovered from patients after extended periods of use in vivo. The molecular properties of these were compared to non -implanted control components, manufactured during approximately the s ame time period, including comparison between mechanically loaded and non-loaded regions of the implants. The results of infrared spectrosco py, dilute solution viscosity and gel permeation chromatography provid ed no evidence of systematic degradation of the Delrin components due to long term exposure to biological fluids and cyclic loading, which w ould indicate the potential for a late decrease in resistance to wear.