Mechanical evaluation of resorbable copolymers for end use as vascular grafts

Nonwoven, nonporous, completely resorbable vascular grafts of selected polymeric composition (3 mm ID) were prepared and evaluated for similarity of mechanical properties to arterial blood vessels. Copolymers of L-lactide, D,L-lactide, and epsilon-caprolactone were selected for diversity of mechanical properties and degradation rates. Two homogeneous grafts were tested: a 50% L-lactide and 50% epsilon-caprolactone copolymer (L-epsilon), and a 70/30 solution blend of L-epsilon copolymer and its corresponding D,L-lactide copolymer (D,L-epsilon). Composite grafts also were tested: 1) a two-layer graft, 2) an alternating layers graft, and 3) a D,L-epsilon graft reinforced with circumferentially wound poly-L-lactide fibers. The resorbable grafts windowed the physiologic range for circumferential Young's modulus and tensile strength, and were kink resistant. The arterial compliance was greater than that of all solid wall resorbable grafts. Incorporation of porosity into the grafts, which is necessary for tissue ingrowth, is expected to lessen this difference.