How to determine the saphenous vein and avoid damage to the femoral vein is a concern for many doctors during varicose vein surgery. The author summarizes the experience of more than a thousand cases over the years and comes up with Zhang’s four criteria for your reference: 1. 2.The saphenous vein with fatty tissue behind the vein is the saphenous vein, and the femoral vein travels within the deep fascia in this area without fat around it. 3.The vein which is easy to raise the incision is the saphenous vein, the femoral vein travels in the deep fascia and the surrounding connective tissue is denser, so it is difficult to lift out the incision. 4.There is often a tiny artery (superficial pubic artery) across the surface before the saphenous vein merges into the femoral vein.