A Free Bypass Flap for Chronic Limb-threatening Ischemia.

Background: 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. Methods: 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. Results: 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). Conclusions: 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.