Mechanical properties of the bioabsorbable polyglycolic acid - Collagen nerve guide tube

Abstract

Bioabsorbable nerve tubes made from polyglycolic acid (PGA) coated with collagen are now used widely for patients who have suffered nerve injury. The main function of nerve tubes is to maintain a space for nerve regeneration in the body against rapid invasion by the surrounding tissue until the new nerve tissue has recovered. However, no precise mechanical testing has ever been carried out on bioabsorbable nerve tubes. The aim of this study was therefore to evaluate the mechanical properties of PGA-collagen tubes and to analyze the degree to which they are able to maintain the patency of the conduit for the recovering nerve. Nerve tubes with diameters of 3 and 4 mm were used in this experiment. The tubes were made from cylindrically woven PGA fibers that had been given 5, 10, or 27 coats of collagen, which was finally crosslinked dehydrothermally at 140°C for 24 h. Both in vitro and in vivo tests were carried out. For in vitro testing, the nerve tube samples were immersed in saline at 37°C for up to 8 weeks. For in vivo testing, samples were implanted subcutaneously into rabbits and observed for up to 16 weeks after implantation. Resistance during compression stress was measured for each sample with the aid of a tensile tester. The collagen coating enhanced the mechanical properties of the tubes, particularly in the first 2 weeks following immersion. The tubes coated with collagen 27 times (27T tubes) were 180% stronger than either the 5T or the 10T tubes. The time taken for the initial mechanical parameters, such as tube rigidity, to be reduced by half was 14 days or more. The reduction in the mechanical strength of the tubes in vivo occurred more rapidly than in vitro. © 2006 Society of Plastics Engineers.