A Free Bypass Flap for Chronic Limb-threatening Ischemia

Recently, significant inframalleolar disease seems to increase in chronic limb-threatening ischemia (CLTI) patients, making identifying sufficient outflow vessels in the foot challenging. In these difficult situations, free tissue transfer is a valuable tool to provide a low-resistance vascular bed to the affected part. However, there remains concern that free tissue transfer may impede adequate perfusion of the higher resistance diseased vascular bed.

To improve perfusion of the affected area directly, the authors have developed a concept of a free bypass flap, adding bypass surgery to free tissue transfer. After anastomosis with the recipient vessels in a conventional manner for free tissue transfer, bypass surgery to the foot is performed by anastomosis of the branch of the flap pedicle with the diseased artery to the foot. A retrospective chart review of nine CLTI patients was performed to analyze the outcomes of free bypass flap transfer between 2018 and 2023.

The flap success rate was 100% (n = 9). Postoperative angiography or echo confirmed the patency of all but one bypass vessel (n = 8). There were six fatalities, however, due to causes other than foot lesions, with an average observation period of 16 months. The limb salvage rate was 89% (n = 8).

A free bypass flap enhances the overall blood circulation to the foot. Due to its high patency rate of bypass vessels, it is a valuable method for preserving the limbs of highly comorbid patients with CLTI.