Bypass surgery to the tibial or pedal vessels has long been applied for treatment of limb-threatening conditions and it has proven to be a successful and durable treatment option for correctly selected patients. In current surgical practice, bypasses performed using high-quality autologous conduit to the tibial or pedal levels demonstrate equivalent long-term patency as bypasses to the popliteal artery. Despite the more aggressive application of endovascular techniques for infrageniculate occlusive disease, tibial or pedal bypass surgery is still the gold standard against which other revascularization treatment options for severe limb ischemia are compared.

Infrageniculate bypass surgery is usually reserved for a manifestation of limb-threatening ischemia, such as rest pain or tissue loss, with or without infection. In clinical practice, the treatment options are limited to optimal medical management, open surgical revascularization, endovascular revascularization, or primary amputation. The choice between options is complex and is based upon comparative estimates of risk and benefit. It should weigh a variety of factors, including but not limited to the patient’s life expectancy, comorbid conditions, anesthetic risk, functional status, severity of ischemia, extent of tissue loss, vein conduit availability, and the underlying arterial anatomy.

The principal distinction between open and endoluminal revascularization strategies is the reduced short-term morbidity for endovascular interventions versus enhanced hemodynamic gain and long-term durability of distal bypass surgery. Endovascular interventions avoid surgical wounds and the associated morbidity and recovery, but major cardiovascular events and periprocedural mortality are broadly similar between
the two. Evidence-based treatment algorithms are a moving target, especially as new generations of endovascular technologies are being developed for clinical applications, such as drug-coated balloons and stents. Nevertheless, the only prospective comparative effectiveness data comes from the BASIL trial, now over a decade old. In this randomized trial of open versus endovascular interventions for advanced limb ischemia, those patients who received a bypass procedure first and survived at least 2 years from the date of intervention had lower mortality and higher amputation free survival in comparison to those patients treated first with endovascular interventions. In addition, patients who required a surgical bypass after a failed endovascular intervention fared worse than those who underwent a bypass first. The overall survival at 2 years was 70%, similar to multiple other prospective studies on critical limb ischemia patients. Taken together, this data as well as the collective literature on limb-threatening conditions suggest that patients who are of appropriate surgical and anesthetic risk and who are projected to survive at least 2 years should preferentially receive a vein bypass for advanced limb ischemia. Higher risk patients with shorter life expectancy, lower functional status, favorable occlusive anatomy, or those who lack adequate autologous conduit options should be considered for endovascular treatment. A new generation of comparative effectiveness studies to re-address this issue, including two large multicenter randomized trials (BEST-CLI, BASIL-2), are underway.

Lack of suitable autogenous conduit is an important relative contraindication, particularly for small caliber, limited outflow targets such as bypass to the lower third of the leg, ankle, or foot. Great saphenous vein of adequate caliber (3 mm or greater) is the optimal conduit for distal bypass; however, lesser saphenous veins, arm veins, and spliced vein grafts all perform reasonably well for limb salvage and are generally superior to prosthetic or alternative conduits (e.g., cryopreserved vein) for very distal bypass grafting. Surgeon judgment to employ such conduits for severe ischemia must recognize the higher failure rates and limited durability of these alternatives.

Infrageniculate arterial reconstructions are not typically applied for intermittent claudication (IC). The evolution of this tenet is predicated upon the historic durability of tibial reconstructions, the morbidity of distal bypass surgery, and the natural history of claudication. Depending on the anatomy of the occlusive disease, distal bypasses for isolated tibial disease may not necessarily bring symptomatic relief to patients with claudication. IC has a relatively benign natural history, with only ∼5% of patients progressing to limb-threatening conditions. Coupled with emerging data that optimal medical management and exercise therapy alone may improve functional performance in IC, the magnitude of benefit for a tibial bypass in claudicants may be marginal. In addition, in the early surgical literature, there was a concern that a failed distal bypass could convert a claudicant to a limb-threatening condition. However, in the modern era, centers of excellence routinely perform distal bypass surgery with low morbidity, and contemporary surgical series routinely report long-term primary patency of vein grafts to distal vessels of over 80% over 5 years. Thus in well-selected patients, a distal bypass for claudication may be appropriate. For example, a saphenous vein bypass to the tibioperoneal trunk in a good risk patient with trifurcation disease can yield durable symptomatic relief.

A detailed understanding of the vascular anatomy is paramount in developing the operative strategy. In general, all hemodynamically significant inflow disease should be treated before embarking on an infrainguinal reconstruction. Noninvasive imaging modalities, such as CT or MR angiograms, are well suited for investigating aortoiliac occlusive disease. However, for distal revascularizations, a digital subtraction angiogram offers the highest resolution of occlusive disease within the tibial vessels and should be routinely performed for all infrageniculate reconstructions. For patients with tissue loss, a detailed understanding of the vascular anatomy of the foot and ankle facilitates decision making in distal target selection and is best assessed with catheter-based angiography with multiple views. Placement of the angiographic catheter in the
most distal vessel and use of power injection aids in adequate visualization of the distal vessels and pedal arch.

Optimal results are achieved not only with pulsatile flow to the foot, but preferably to the angiosome directly supplying the region of major tissue loss. The angiosome concept, derived from reconstructive plastic surgery principles, divides the body into distinct three-dimensional blocks of tissue perfused by a source artery. Cadaveric studies have mapped out six distinct angiosomes of the foot and ankle, derived from the peroneal, anterior tibial, and posterior tibial arteries. A bypass to the source artery of an angiosome that harbors a wound has been shown to hasten wound healing in comparison to a bypass to a tibial artery that is not in direct continuity with the angiosome in question. However, collateral pathways via “choke” vessels are often present and the quality of the pedal arch may be a more important determinant than the angiosome per se for some foot lesions. The angiosome consideration for surgical planning should be a relative one, and may be of greater relevance to endovascular approaches in comparison to bypass surgery. Thus if a bypass to the source artery for the angiosome in question is not possible, the tibial vessel continuous to the foot should be chosen as the outflow. Bypasses to a well-collateralized peroneal artery have been shown to fare equally well as bypasses to other tibial vessels for wound healing, limb salvage, and graft patency. Other studies have shown that bypass to the dorsalis pedis can be effective in patients with heel ulceration.

Preoperative planning should also evaluate the conduit availability, generally using duplex ultrasound vein mapping. Both lower extremities should be evaluated. In settings where the GSV is known to be absent or of poor quality, arm veins should also be mapped. It is advisable to repeat the ultrasound examination in the operating room prior to prepping to confirm the findings and also noted the anatomy for planning of incisions. Always be prepared to have the next most promising extremity available for harvest if intraoperative findings demonstrate a marginal or inadequate segment. In the case of arm vein, this will require discussion with anesthetist to prevent placement of lines and catheters in an extremity that may be required for harvest.