Fascial interposition is a technique where the layer of fascia between the vas deferens ends is sutured to physically separate them after division. This prevents spontaneous recanalization, a common cause of vasectomy failure. Studies show that adding fascial interposition significantly reduces the risk of vas deferens reconnection compared to simple ligation or no ligation. Unlike electrocautery alone, fascial interposition provides a reliable mechanical barrier, making it the most effective method to ensure long-term occlusion and sterility.

Reference: Campbell-Walsh Urology, 12th Edition.