RABBIT MUSCLE AND URETHRAL IN SITU BIOCOMPATIBILITY PROPERTIES OF THE SELF-REINFORCED L-LACTIDE-GLYCOLIC ACID COPOLYMER 80: 20 SPIRAL STENT

Abstract

A new type of self-reinforced L-lactide-glycolic acid copolymer, molar ratio 80:20, stent was developed. We evaluated the tissue biocompatibility properties of the new material. Rods made of self-reinforced L-lactide-glycolic acid copolymer were inserted into rabbit dorsal muscles and rods of latex or polyvinylchloride and silicone served as positive and negative controls, respectively. Urethral stents of self-reinforced L-lactide-glycolic acid copolymer and steel were inserted in situ via cystoscopy into the rabbit prostatic urethra. The animals were sacrificed after 2 weeks, 1, 2 and 3 months, respectively. In situ histological analysis was done. Tissue reactions around the implantation types were analyzed histologically and scored semiquantitatively. In addition, macroscopic analysis was done of the urethral in situ stents. In rabbit muscle implantation test tissue reaction to the self-reinforced L-lactide-glycolic acid copolymer stent resembled that of negative control silicone. Less than moderate chronic inflammatory changes gradually subsided after 2 weeks. Foreign materials in the tissue and the reaction to these materials began to disappear after 1 month and at 3 months were completely absent. All rabbits fitted with the stent voided normally postoperatively. Self-reinforced L-lactide-glycolic acid copolymer stents were soft, partially fragmented and easily disintegrated when touched at 2 months, and were almost completely degraded at 3 months. The material did not encroach into the urethral wall macroscopically or microscopically. No calcification on the self-reinforced L-lactide-glycolic acid copolymer stents or bladder stone formation was seen. The new self-reinforced L-lactide-glycolic acid copolymer 80:20 material is safe, highly biocompatible and suited for future clinical use. It is most appropriate for preventing postoperative urinary retention after most minimally invasive thermal treatments for benign prostatic hyperplasia.