Fabrication and characterization of small-diameter vascular prostheses.

We have developed a process to fabricate polyurethane vascular grafts of various dimensions and porosities in our laboratory. A primary feature of the presented fabrication technique is the ability to control surface porosity and roughness, and bulk mechanical properties. The method is based on the spray application of a fine mixture of polymer solution and nitrogen gas bubbles onto a lathe-mounted mandrel. The technique was successfully tested with Tecoflex, a linear segmented aliphatic polyurethane. Other urethane polymers can be used as well. Several polymer coats are applied in a semiautomated process, at the end of which the polymer coating is dried and the tube is slipped off the mandrel. It is the purpose of this paper to describe the fabrication process and present results of the evaluation of grafts. Wall structure was evaluated using scanning electron microscopy and compliance was measured in a specially designed testing apparatus. We developed methods to quantify kink resistance and suture retention capacity of the grafts. These characteristics were correlated with graft fabrication variables: mandrel rpm, horizontal speed of the spray nozzle, gas and polymer solution flow rates. We were able to routinely produce 3-6-mm-ID grafts with 0.5-1.2-mm wall thickness and average bulk pore sizes of 10-250 microns; the wall porosity could be varied between 30 and 70%. Compliance values of the grafts were comparable with corresponding values of carotid and femoral arteries of dogs.