Femoral-Popliteal Bypass

Femoral-popliteal bypass restores arterial flow to the lower extremity in patients with disabling claudication or critical limb-threatening ischemia (CLTI) due to superficial femoral artery (SFA) occlusion or severe stenosis. CLTI manifests as ischemic rest pain, non-healing ulcers, or tissue loss/gangrene — and warrants revascularization to prevent amputation.

Patient selection has shifted with the rise of endovascular therapy. Most SFA disease is now treated initially with angioplasty and stenting; bypass is reserved for patients in whom endovascular therapy has failed, is not anatomically feasible (long occlusions, heavily calcified vessels), or in whom durable patency is critical. The BEST-CLI trial provides modern evidence for surgical bypass with vein conduit in selected CLTI patients.

Disabling intermittent claudication may be an indication after failure of structured exercise, smoking cessation, and medical therapy — but the bar for surgical intervention in claudication alone is high because of the morbidity of the operation relative to a non-limb-threatening symptom.

Workup includes ankle-brachial index (ABI) measurement, segmental pressures with pulse volume recordings, and arterial imaging — typically duplex ultrasound followed by CT angiography or formal contrast angiography. Vein mapping by ultrasound is essential before any planned vein bypass: the great saphenous vein is preferred, and the surgeon must confirm adequate caliber (>3 mm) and continuity from the groin to below the knee.

Cardiac assessment is essential because patients with peripheral arterial disease have a high prevalence of coronary disease. Smoking cessation, statin therapy, antiplatelet therapy (aspirin), and blood pressure and diabetes optimization are standard preoperative measures.

The great saphenous vein is the conduit of choice, particularly for below-knee bypass. Patency rates are markedly higher with vein than with prosthetic conduit, especially in the long term and for below-knee targets. The vein can be used reversed (cut, flipped, and sewn so flow is in the direction of valve opening), nonreversed (with valve lysis using a valvulotome), or as an in-situ bypass (vein left in its native bed with valves lysed and side branches ligated).

When saphenous vein is unavailable (prior harvest, varicosities, inadequate caliber), options include arm vein (basilic or cephalic), composite vein constructs, or prosthetic conduit (PTFE or Dacron). For above-knee bypass, prosthetic conduit has acceptable patency and is reasonable when vein is poor. For below-knee bypass, vein is strongly preferred — prosthetic below-knee patency is poor.

The patient is positioned supine with the leg slightly externally rotated. The vein is harvested through one or more incisions along its course, marking branches as it is dissected. The common femoral artery is exposed in the groin. The popliteal artery is exposed through a medial thigh incision (for above-knee anastomosis) or below the knee through a medial calf incision (for below-knee anastomosis).

Systemic anticoagulation with heparin is administered. The proximal anastomosis to the common femoral artery is performed first, typically end-to-side with the heel of the vein at the toe of the arteriotomy. The vein is tunneled subcutaneously or in the anatomic plane between the muscles to the distal target. The distal anastomosis is performed similarly. Hemostasis is confirmed and intraoperative completion imaging (duplex or angiography) verifies patency and absence of technical errors before closure.

Pulses are checked at the bedside immediately after surgery and serially in the first 24 hours. Loss of distal pulse demands urgent evaluation — early graft thrombosis is often technical and amenable to thrombectomy and revision. Aspirin is continued lifelong; some patients benefit from additional antiplatelet (clopidogrel) or anticoagulation, particularly when graft outflow is poor.

Duplex surveillance every 3–6 months for the first year and at least annually thereafter is standard. Identification of in-graft or anastomotic stenosis before frank thrombosis allows intervention with angioplasty or surgical revision, preserving the graft.

Primary patency at 5 years for vein bypass is approximately 65–75% above the knee and 50–65% below the knee. Prosthetic above-knee bypass achieves about 50–60% at 5 years; below-knee prosthetic patency is much lower. Limb salvage rates are higher than patency rates because secondary interventions and even occluded grafts may not result in amputation if collateral circulation has developed.

Operative complications include bleeding, lymphocele or lymph leak (especially after groin dissection), wound infection (high risk in the groin), graft infection (a feared complication, especially with prosthetic — may require graft excision and extra-anatomic bypass), and acute graft thrombosis. Late complications include progressive in-graft stenosis, distal disease progression, and recurrent rest pain or tissue loss.

Examiners focus on the choice of conduit, the difference in vein vs prosthetic patency, surveillance strategy, and management of the patient with a thrombosed graft — including the decision between thrombectomy/revision and a new bypass.