Infrapopliteal Bypass Technique

Infrapopliteal bypass involves establishing inline arterial flow to target vessels such as the tibial, peroneal, or pedal arteries, using the common femoral, deep femoral (profunda femoris), superficial femoral, or popliteal artery (or, occasionally, a tibial artery) as the inflow vessel. The video below demonstrates a bypass from the popliteal artery to the dorsalis pedis.

Exposure of vessels

Proximal femoral artery and its branches

Longitudinal or oblique groin incisions are used for the femoral exposure. The incision is carried along the femoral pulse at the level of the common femoral artery (the inguinal ligament is often used as the landmark for the proximal common femoral artery).

Subcutaneous tissues are dissected and the femoral sheath entered. The artery lies lateral to the femoral vein. The common, superficial, and deep femoral (profunda femoris) arteries are dissected and controlled with vessel loops.

Attention is paid to preserving flow to and avoiding injury to the deep femoral artery during dissection. Care must also be taken in mobilizing and identifying the lateral circumflex femoral vein to avoid injury. Circumflex branches to the femoral artery are controlled and preserved.

A more proximal dissection to the external iliac artery may be required if vascular clamps cannot be safely applied to the common femoral artery. To facilitate this exposure, the inguinal ligament may have to be divided. This is repaired at the completion of the bypass reconstruction.

A significantly diseased femoral artery may require an endarterectomy with subsequent angioplasty in order to make it suitable for bypass grafting.

Distal femoral artery and above-knee popliteal artery

The knee is flexed and a roll placed underneath the thigh. A longitudinal skin incision is made in the lower medial thigh at the intermuscular groove between the superior edge of the sartorius and the inferior edge of the vastus medialis. Care is taken in avoiding injury to the great saphenous vein (GSV), which runs close to this area.

Fascia is incised longitudinally, and the sartorius is reflected posteriorly, along with the semitendinosus and the gracilis. The adductor magnus is retracted anteriorly and the adductor canal exposed. The popliteal fat pad is exposed, and careful dissection is performed close to the femur to identify the artery and vein (see the image below).

Below-knee popliteal artery

The knee is flexed, and a roll is placed underneath the thigh. A longitudinal incision is made 1-2 cm below the posterior edge of the tibia just distal to the medial tibial condyle and extended as needed (typically 10-12 cm). Care is taken in preserving the GSV.

The fascia overlying the gastrocnemius is incised longitudinally. The plane between the soleus and the gastrocnemius is developed. The soleus is retracted anteriorly; the gastrocnemius is retracted posteriorly. (See the image below.) The below-knee popliteal space is entered, and the artery is typically seen to be surrounded by two veins. The tibial nerve is posterior to the vascular bundle. Sharp dissection is carried out to delineate the anterior tibial artery and the tibioperoneal trunk. The soleus may have to be divided to afford further exposure.

Posterior tibial and peroneal arteries

The knee is flexed and rotated laterally. A roll is placed below the calf. A longitudinal incision is made 1-2 cm below the posterior edge of the tibia in the midleg and is extended proximally or distally as needed. This incision overlies the course of the GSV; care is taken to avoid injury to the vein during this exposure. The incision is carried down to the fascia, whereupon the fascia is incised and the gastrocnemius is mobilized and retracted posteriorly.

Soleus muscle attachments to the tibial edge are divided, allowing entrance to the deep posterior compartment. The posterior tibial artery should be accessible and is generally surrounded by a pair of tibial veins. The peroneal artery lies deeper to the tibial vascular bundle within this compartment (see the image below).

Anterior tibial artery

The knee is flexed with a roll underneath the calf. A longitudinal incision is made in the skin overlying the plane between the tibialis anterior and the extensor digitorum longus, to be extended as needed. The intermuscular groove is entered. The anterior tibial artery courses along with the deep peroneal nerve just superficial to the interosseus membrane. Again, the artery is typically enveloped by a network of tibial veins (generally paired).

Pedal arteries

Pedal vessels are relatively easy to identify because they are superficial. A Doppler probe can aid in identifying the location of both the dorsalis pedis artery and the distal posterior tibial artery. A longitudinal incision is made overlying the course of the vessels for exposure.

Preparation of conduit

If a GSV is deemed suitable as a bypass conduit, the vein can be completely mobilized and then reversed; alternatively, the vein can be left nonreversed, which requires subsequent lysis of the valves. If the inflow site is in the ipsilateral groin, the vein can also be left in situ and not mobilized from its bed; this technique also requires lysis of the valves.

An adequate conduit vein is mapped and marked preoperatively. The vein is then exposed through medial incisions that overlie the course of the vein. Tributaries to the vein are carefully ligated with silk ties. The vein is then gently distended, and any leaks are addressed. The vein is placed in heparinized saline until one is ready to construct the bypass.

With the in-situ bypass, the vein is exposed and not mobilized from its bed, except at the proximal and distal ends. As the vein is exposed, tributaries are tied off with silk ties. The proximal vein is mobilized, and the first valve is excised under direct vision. Once this is done, the proximal anastomosis can be performed.

Once the proximal anastomosis is complete and flow is established to the conduit, the first competent valve impedes flow. A valvulotome is then used to perform careful lysis of the valves. Preserving select side branches to allow passage of the valvulotome is important.

Alternatively, the GSV may be harvested endoscopically, which minimizes the incision length on the leg of the patient. In this technique, the vein is harvested with the aid of an insufflation device and laparoscopic camera. Once the vein is removed from its bed, the tributaries are ligated, much as with the open method described above. ^[16]

Tunneling of graft

Before systemic heparinization, graft tunneling is performed. A graft tunneling device (eg, Gore Tunneler; W. L. Gore, Newark, DE) is generally used to create tunnels. Tunneling can be anatomic or subcutaneous, depending on the target vessel. The diameter of the tunneling instrument must be sufficient to create a tunnel wide enough to prevent compression of the graft. The route for tunneling to the posterior tibial artery or peroneal artery can be anatomic or subcutaneous.

The anatomic route follows the posterior edge of the sartorius, enters the popliteal fossa between the two heads of the gastrocnemius, and passes anterior to the soleus to the posterior tibial artery. This is the preferred tunneling route for reversed saphenous or prosthetic grafts. The graft is less subjected to kinking when routed anatomically. In the subcutaneous route, a tunnel is made that runs along the anterior medial surface of the thigh, then the medial side of the knee and leg. The aponeurosis of the leg should be incised enough to avoid sharp angulation of the graft as it enters the target vessel.

The route for tunneling to the anterior tibial artery can also be anatomic or subcutaneous. Subcutaneous tunneling may be technically easier and courses anterolaterally at the lower thigh and lateral side of the knee and leg. For in-situ bypasses, the lower part of the popliteal fossa is divided, and the interosseous membrane is freed and incised longitudinally to allow passage of the graft to the anterior compartment. The distal anastomosis is constructed at a point that avoids sharp angulation as the graft exits the interosseous tunnel.

Construction of bypass

The patient is heparinized systemically with 80 units/kg of heparin before the inflow vessel is occluded. The activated clotting time is maintained above 250 seconds to prevent thrombotic complications. Longitudinal arteriotomies are made on the artery and extended with angled Potts scissors. The graft is spatulated, and typically, an end-to-side anastomosis is created with 5-0 or 6-0 polypropylene suture (see the image below).

After completion of the proximal anastomosis, flow is established through the graft, and its adequacy is confirmed. Vein grafts are left distended and marked for orientation. The graft is passed carefully through the tunnel in such a way as to ensure that there are no kinks or twists.

Before construction of the distal anastomosis, the lie of the graft is carefully assessed with the leg extended. The goal is to keep the graft as parallel to the target vessel as possible; this may necessitate modifications to the tunneling and further dissection and mobilization of the surrounding muscular aponeurosis.

Once length and lie are assessed, the graft is cut to size and the end spatulated. The anastomosis is then created in an end-to-side fashion with a continuous polypropylene suture; for tibial and pedal vessels, 6-0 or 7-0 polypropylene sutures are typically used. Before the completion of the anastomosis, the artery is back-bled and the graft flushed.

Once the anastomosis is complete, the bypass is carefully examined. The authors' center typically performs completion arteriography after the construction of the distal anastomosis. Some centers perform intraoperative duplex ultrasonography (US).

Hemostasis is thoroughly ensured in the wounds. The groin wound is closed in multiple layers of polyglactin suture to obliterate potential space. The leg wounds are closed in layers with polyglactin suture for the fascial and dermal layer. Skin can be approximated with staples or nylon suture on either site.

Doppler US signals should be checked frequently, and routine bedside ankle-brachial indices (ABIs) are obtained daily to monitor graft patency if pedal pulses cannot be palpated after the reconstruction. Any question regarding graft patency should prompt the performance of duplex US or another imaging investigation.

Patients are maintained on an antiplatelet agent, a beta blocker, and a statin. A study by Gupta et al suggested that dual antiplatelet therapy (DAPT) may have an advantage over single antiplatelet therapy (SAPT) after bypass when prothetic grafts are used, but not when vein grafts are used. ^[17]  In a study comparing SAPT, DAPT, and anticoagulation in Medicare beneficiaries who had undergone infrapopliteal bypass for CLI, Marcaccio et al found that as compared with SAPT, DAPT and anticoagulation therapy were not associated with improved outcomes. ^[18]

Systemic anticoagulation is reserved for high-risk grafts (because the risk of major bleeding is significant), reoperative cases, poor arterial runoff, and distal bypasses using prosthetic or suboptimal vein graft. Perioperative antibiotics are stopped 24 hours after surgery unless active infection is present. Patients with significant edema are treated with ACE compression (avoided with in-situ or subcutaneous vein grafts) and leg elevation.

Potential complications of infrapopliteal bypass include the following:

• Lymphatic leak
• Bleeding/hematoma
• Graft thrombosis
• Graft infection

Early graft thrombosis and delayed pseudoaneurysm of the graft may be a sign of underlying graft infection.

If an initial distal bypass fails, a redo bypass may be considered; however, patency and survival appear to be significantly lower. ^[19]