Expansion and bioabsorption of the self-reinforced lactic and glycolic acid copolymer prostatic spiral stent

Purpose: Self-reinforced bioabsorbable stents can be made self-expanding du e to the viscoelastic memory of the oriented bioabsorbable materials. A new self-expandable self-reinforced copolymer of lactic/glycolic acid, lactic/ glycolic molar ratio 80:20 stent was developed to prevent postoperative uri nary retention after procedures that induced prostatic edema. In in vitro e xperiments the expansion rate has been up to 100% during the first few hour s at body temperature. We investigated the expansion rate and biodegradatio n of the self-reinforced lactic and glycolic acid copolymer prostatic spira l stent in vivo in the prostatic urethra. Materials and Methods: A total of 39 men, 52 to 84 years old, with lower ur inary tract symptoms due to benign prostatic enlargement underwent intersti tial laser coagulation of the prostate. A self-reinforced copolymer of lact ic/glycolic acid, lactic/glycolic molar ratio 80/20 stent was inserted into the prostatic urethra at the end of the operation. The stent lumen diamete r was 4.5 mm. The location and diameter of the lumen and degradation of the stent were studied with transrectal ultrasound at 1, 2, 4 and 6 months pos toperatively. At 6 months patients underwent cystoscopy. Results: All except 1 patient voided on postoperative day 1. Mean lumen dia meter was 7.4 mm. (range 6.2 to 8.2) at 1 month and 7.2 min (range 6.2 to 7 .5) at 2 months. At 4 months the stent was degraded into small pieces. No p ieces of stent were found in the prostatic urethra on ultrasound or cystosc opy at 6 months. However, a portion of the spiral stent was found at the bo ttom of the bladder in 2 patients. Conclusions: The speed and expansion rate of the self-reinforced copolymer of lactic/glycolic acid, lactic/glycolic molar ratio 80/20 stent was suffic ient to lock the stent in place and ensure voiding in cases of edema induce d bladder outlet obstruction. Strength retention greater than 2 months was long enough to avoid later impairments of voiding.