A resorbable bicomponent braided ureteral stent with improved mechanical performance

Bioresorbable ureteral stents have the advantage of eliminating the need for a second removal surgery and hence avoiding certain complications. However the inadequate mechanical performance and lack of control over the rate of resorption limit the use of current prototype designs. This paper focuses on a series of resorbable millimeter-sized stents which were fabricated by a unique combination of braiding and thermal treatment processes. Their mechanical properties where optimized by varying the braided structure and different resorbable components. Five different bicomponent structures were fabricated for the stent with different areas and distributions of poly (glycolic acid) (PGA) and poly (lactic-co-glycolic acid) (PLGA) resorbable yarns. Subsequent thermal treatment then converted the PLGA yarns into areas of continuous PLGA polymer film. The morphology, applied compression resistance and recovery and tensile strength tests were conducted on these prototype stents so as to investigate the relationship between their structures and mechanical properties. By selecting the appropriate resorbable biomaterials and altering the design of the braided structure it was possible to generate different sized areas and distributions of 100% braided yarn and 100% polymer film within the same bicomponent tubular structure. The relative total area of braided yarn to polymer film coverage was different for the five different prototype stents as well as between the external and internal surfaces of the bicomponent stents. This relative coverage of the braided yarn to polymer film played an important role in determining the mechanical performance of the stents, including the compression and recovery behavior as well as the tensile properties and failure morphology. The design of Stent C appeared to have the optimal structure for a resorbable ureteral stent with superior applied compression and tensile properties.