Which is the best vascular prosthesis below the inguinal ligament?

Prostheses made of P.T.F.E give reasonable results when used as femoropopliteal bypass below the inguinal ligament and above the knee joint in patients with good "run-off". Human umbilical vein will probably give similar results but with reservations about its degradability. A compliant tube made from a non biodegradable stable polymer and which has a non thrombogenic internal surface seems to offer the most likely improvement.