Distal bypass requires careful assessment of the extent of arterial disease as well as detailed anatomic characterization of the inflow and outflow arteries. Computed tomographic angiography (CTA) is being used with increasing frequency; however in the authors’ experience, its utility for planning distal bypass is limited due to the small caliber of the crural vessels which are often calcified. Magnetic resonance angiography (MRA) provides reasonable imaging and is not affected by arterial wall calcification but has inferior resolution to either CTA or conventional angiography. Moreover, high-quality MRA in the periphery requires the use of gadolinium contrast which is contraindicated in patients with chronic kidney disease due to the risk of nephrogenic systemic sclerosis (NSF). In the authors’ opinion digital subtraction angiography remains the gold standard preoperative imaging prior to distal bypass. It provides the best image resolution and is the only modality that allows the simultaneous acquisition of anatomic imaging and catheter-based treatment. Appropriate lower extremity angiography for distal bypass requires imaging of the entire arterial tree from the aorta to the base of the toes. Proper imaging of the distal tibial vessels and pedal arteries requires magnified anterior posterior and lateral views to fully assess the quality of the vessels.

Contrast arteriography is invasive, exposes the patient and surgeon to ionizing radiation and may result in complications from femoral access and/or vessel perforation. Consequently, it should only be performed after the decision to intervene has already been made. Contrast-related complications include contrast-induced renal insufficiency and allergic reactions. Patients with underlying renal insufficiency are most at risk for contrast-induced renal failure. Any patient with an elevated creatinine (greater than 1.5 mg/dL) or an estimated GFR less than 30 should be treated with intravenous fluid hydration and/or sodium bicarbonate infusion prior to the procedure. Sodium bicarbonate infusion has been shown to have a better protective effect against contrast-induced nephropathy than sodium chloride infusion alone. The patient should be pretreated with sodium bicarbonate at a concentration of 150 mEq/L in D5W solution given as a bolus of 3 mL/kg/hr for 1 hour prior to the procedure and 1 mL/kg/hr for 6 hours after the procedure.

There is near universal agreement that autogenous vein is the best conduit for distal bypass. Numerous clinical trials have demonstrated superior patency and durability with vein compared to prosthetic grafts. Vein grafts are resistant to infection and due to the presence of viable endothelium, will remain patent even when inflow or outflow is compromised. Gentle handling and meticulous harvesting to minimize graft injury are critical principles. Damaged, poor quality conduit often fails quickly and even if it does not, rarely has good long-term patency due to the formation of intimal hyperplasia in areas injured during harvesting. In the authors’ opinion, the quality of the bypass conduit is the most important determinant of success with distal bypass.

The greater saphenous vein is the most readily available and durable conduit. Preoperative assessment of the availability and quality of the greater saphenous vein is
critical for a successful outcome. Recent studies have demonstrated a positive relationship between vein graft diameter and patency, with veins less than 3 mm in diameter demonstrating inferior patency. Calcified, sclerotic veins and veins with segments of recanalized organized thrombus, strictures, and varicosities are also prone to early thrombosis or later failure from intimal hyperplasia. Duplex mapping of the greater saphenous vein should be performed in all patients prior to surgery. If the ipsilateral greater saphenous vein is absent or unsuitable, the ipsilateral small saphenous vein, the contralateral greater and small saphenous veins, and upper extremity veins should all be imaged to determine their suitability. Duplex scanning of the vein can determine its diameter and the presence of pathology rendering it unsuitable as an arterial conduit.

Adequate exposure of the common femoral artery and branches is best accomplished through a vertical incision. The skin incision is made directly over the femoral pulse and extended over the groin crease to the level of the inguinal ligament. When the femoral pulse cannot be palpated the incision should be made one-third of the way from the medial side of the inguinal ligament. Division of the subcutaneous tissue can be done with the electrocautery; however, it is recommended to ligate any superficial lymphatics encountered to reduce the risk of postoperative lymphocele. The femoral sheath is usually encountered about a centimeter medial to the medial edge of the sartorius muscle. Exposing the sartorius is indicative of being too lateral. Care must be taken to avoid injury to the femoral nerve when opening the femoral sheath. It is generally best to identify the artery first and then extend the exposure proximally and distally on the anterior surface of the artery to avoid injury to the nerve laterally and the vein medially. The proximal extent of the dissection should be the inguinal ligament. The common femoral artery divides into two major trunks: The deep and superficial femoral arteries. These are best exposed by dissecting distally along the anterior surface of the common femoral artery to its bifurcation into the superficial femoral artery and deep femoral artery. Identification of the superficial femoral artery is straightforward. It extends inferiorly from the common femoral artery and is noticeably smaller in caliber. The origin of the deep femoral artery is most often found lateral and slightly posterior to the origin of the superficial femoral artery. Adequate exposure occasionally requires division of the lateral femoral circumflex vein which crosses anterior to the deep femoral artery 1 or 2 cm distal to its origin. The common femoral, deep femoral, and superficial femoral arteries are then encircled with vessel loops (Fig. 25.1).

The posterior tibial artery is easily accessible through a medial leg incision. It can often be exposed through the same leg incision that is used for the greater saphenous vein harvest. In the proximal calf, the posterior tibial artery runs through the deep posterior compartment, deep to the soleus muscle, which must be divided close to its insertion on the tibia to gain access to the compartment. In the distal one-third of the lower leg, distal to the lower edge of the soleus, the posterior tibial artery is more easily accessible under the deep fascia separating the superficial and deep posterior compartments, anterior to the flexors of the toes and foot. At the level of the ankle, it can be exposed through a vertical incision medial to the calcaneus tendon. The artery is often surrounded by a plexus of vein branches connecting to the main venous trunks. Several vein branches may require ligation to expose an adequate length of the artery for bypass.

The anterior tibial artery perforates the interosseous membrane and courses along its lateral surface in close proximity to the tibia. It is exposed through a vertical incision over the dividing line between the lateral and anterior compartments. The deep fascia
can be incised, developing a plane between the tibialis anterior and extensor hallucis longus muscle tendons. Dividing the superior extensor retinaculum facilitates separation of the tendons (Fig. 25.2). Grafts can be tunneled through the interosseus membrane, which can occasionally cause troublesome bleeding or be tunneled across the subcutaneous space in the thigh and calf. The peroneal artery is relatively difficult to isolate and has only indirect communication with the arteries of the foot; thus it should not be used in preference to suitable tibial arteries. The artery courses in the deep posterior compartment in close proximity to the medial side of the fibula and posterolateral to the posterior tibial neurovascular bundle. It can be approached through either a medial or lateral incision. To approach the peroneal artery from the medial side, the patient is placed in the supine position with the leg externally rotated and the knee on a bump. A vertical incision is made 2 cm behind the posterior border of the tibia in the middle third of the leg. The incision is deepened through the crural fascia and the tibial attachments of the soleus muscle are divided. The soleus muscle is then retracted posteriorly to expose the flexor
digitorum longus muscle posterior to the tibia. The deep posterior compartment is entered by incising the fascia covering the flexor digitorum longus muscle. To prevent injury to the muscular branches of the posterior tibial vessels, the neurovascular bundle is best left in the loose areolar tissue overlying the soleus muscle. The artery can be approached either anterior or posterior to the posterior tibial neurovascular bundle. It is best identified by palpating the fibula and using a hand-held Doppler to identify its precise location usually on the anterior surface of the flexor hallucis longus muscle. To approach the peroneal artery from the lateral side the patient is placed in the supine position with the leg internally rotated. An incision is made on the lateral leg overlying the fibula, centered over the area of intended anastomosis. The incision is continued through the subcutaneous tissue and deep fascia. The muscular attachments to the fibula are then separated using a periosteal elevator circumferentially. Great care should be used during dissection of the medial surface of the fibula because the peroneal vessels are in close proximity. The bone is then resected and removed from its bed. The peroneal vessels are then located deep to the fibula bed (Fig. 25.3).