General Considerations and Indications for Treatment
The management of tibioperoneal occlusive disease is among one the most medically and surgically challenging problems in vascular surgery. Important factors to consider when approaching patients with this disease include the patient’s general health, coexisting medical conditions and overall functional status. Arterial occlusive disease in any one location is rarely an isolated entity and instead is usually associated with varying degrees of generalized atherosclerotic disease. Medical comorbidities are also common in this patient population. As a result of atherosclerotic disease in other locations and medical comorbidities, patients with tibioperoneal disease are predisposed to increased operative risk and poor medical outcomes. Diabetes mellitus, which coexists in approximately 60% of patients with tibioperoneal disease, results in calcified vessels increasing the difficulty of interventions. Multilevel disease further augments the complexity of interventions since extensive infrapopliteal collateralization prevents earlier disease recognition. Lastly, the treatment options for this disease are accompanied by the frequent need for re-intervention.
The medical and surgical complexity of this disease and the high risks of intervention should mandate conservative surgical decision making. While patients with tibioperoneal disease may present with claudication, the ultimate decision to intervene should be reserved for patients with signs of impending limb loss manifested by ischemic rest pain, non-healing soft tissue ulceration and gangrene. In this subset of patients, who otherwise maintain a functional status, avoidance of amputation is paramount. Amputation in the elderly is associated with significant consequences including loss of independence and decreased quality of life. Further, the medical costs of amputation rival even the most extensive interventions for tibioperoneal disease making avoidance of amputation a worthy undertaking not only for the patient, but also for society.
The goals of pre-operative evaluation include identification of patients who are to likely benefit from tibioperoneal intervention, development of interventional plans individualized to each patient’s disease extent, and consideration of comorbidities to allow medical optimization prior to surgery.
Assessment should always begin with a thorough history and physical including assessment of functional status. The mean age for patients presenting with this disease is greater than 70 years. Medical comorbidities in this patient population are the rule not the exception. Patients often present with apparent or occult diabetes, renal insufficiency, cardiovascular disease and cerebrovascular disease. Optimization of medical comorbidities is advised pre-operatively when possible. We do not routinely perform full cardiac evaluation in otherwise asymptomatic patients prior to intervention as it has been demonstrated that these operations can be performed safely without this. In fact, delay for cardiac evaluation has been shown to result in higher amputation rates secondary to progression of ischemia and infection in patients who may have benefited from limb salvage interventions. Monitoring of renal function is essential as temporary worsening of renal function associated with contrast nephropathy after angiography is a frequent occurrence. With proper management however, most renal insufficiency is transient.
Physical exam should include assessment of bilateral lower extremity pulses, wounds, extent of lower extremity infections and coexistent venous disease. If intervention is planned, diligent control of foot sepsis with surgical debridement of infected tissue and antibiotics should be done pre-intervention. Toe amputations may be required and should, in most cases, be left open to drain. Final foot reconstruction can be performed post-operatively after blood flow is restored.
Non-invasive vascular imaging including ankle-brachial indices and toe pressures should be used to objectively document the degree of ischemia and serve as a baseline for comparison post-operatively. An ankle pressure below 50 mm HG with a flat pulse wave form indicates that the patient is unlikely to heal foot wounds without prior revascularization. More detailed imaging including conventional angiography, computed tomographic angiography (CTA) or magnetic resonance arteriography (MRA) should additionally be completed and reviewed prior to consideration for intervention. Delayed images may be helpful in patients with poor runoff. CTA and MRA may provide more detailed imaging of the distal circulation than routine angiography and is our preferred method for pre-operative assessment. Imaging should be obtained from the aorta distal to the renal arteries through the pedal vessels with attention paid to the quality of inflow vessels, degree of multifocality of disease, vessel calcification and vessel runoff. The number of patent tibial vessels is associated with improved success of revascularization. At a minimum, restoration of blood flow for wound healing or resolution of rest pain typically requires at least one continuous vessel providing in-line flow to the foot. If this is not possible, then revascularization to restore the vessel most likely to provide flow to the wound is indicated.
If the patient is a potential distal bypass candidate, non-invasive evaluation of the bilateral lower extremity venous systems should be done to evaluate for bypass conduits. Upper extremity duplex ultrasonography may also reveal suitable veins for bypass procedures should the greater or lesser saphenous prove unusable.
During the evaluation it should be remembered that primary amputation may be more advisable in patients who are non-ambulatory, of limited functional status, have severe flexion contractures, in those with predetermined prohibitive medical risks, and in patients with unsalvageable lower extremity infections. Of note, age, most medical problems, incurable malignancy, and a contralateral amputation are not absolute contraindications for tibioperoneal intervention.
Acutely threatened limbs may benefit from systemic heparinization or thrombolytics prior to either operative or endovascular intervention. This is a judgment call and depends on the acuity of presentation and the severity of ischemia. Aspirin and an ADP-receptor inhibitor, clopidogrel or dipyridamole, should also be initiated at least 5 days prior to all elective endovascular interventions. We preferentially use clopidogrel in our patients. In those patients who require more urgent intervention or did not complete their course of clopidogrel as instructed, clopidogrel loading can be done the same day. When elective circumstances prevail, we also routinely start our bypass patients on aspirin and clopidogrel pre-operatively. However, it is not our routine practice to clopidogrel load bypass patients if they have not already been taking this medication.
Tibial Artery Bypass
Outflow – Distal Bypass Target
Distal bypasses may be performed to the posterior tibial, anterior tibial or peroneal arteries. Alternatively, bypass may be performed to the pedal vessels of the foot. All things considered, the most proximal vessel, with the least disease, that can provide in-line flow to the foot is chosen.
Choice of inflow vessel is determined by prior surgical interventions, characteristics of the inflow vessel, and length of available autogenous vein. The common femoral artery is a common location for the inflow anastomosis. If this vessel is heavily calcified or scarred in from prior surgery, the surgeon can alternatively utilize the distal external iliac, profunda femoris, superficial femoral or above-the-knee popliteal arteries. The profunda femoris, superficial femoral and popliteal arteries may also be used if limited by length of the available conduit. It is paramount that a tension free anastomosis is constructed in order to avoid future pseudoaneurysms. Alternatively a previous bypass conduit used for a femoral-femoral, axillary-femoral or aorto-femoral bypass may be used for a proximal anastomosis.
Autogenous vein is the preferential conduit for distal bypasses. The order of preference is the greater saphenous vein, lesser saphenous vein, followed by arm vein. While the cephalic and basilic veins are definite options for bypass, they are listed last since they are generally thin walled, often have fibrotic segments from previous venipuncture, and have lower patency rates compared to lower extremity veins. The venous segment may be used in reversed (Figure 1) or in-situ fashion. Regardless of the vein source, distended vein diameters of at least 3 mm are recommended. Both techniques require ligation of venous side branches and the in-situ technique requires lysing of venous valves. Veins with a single kink or twist can still be used but require intraoperative repair prior to bypass.
Use of expanded polytetrafouroethylene (ePTFE) below the knee is discouraged when alternatives exist since both patency and limb salvage rates lag significantly behind bypasses performed using autogenous vein. Segments of vein may be pieced together if a single, long continuous vein is unavailable. However, patency rates using multi-vein segment bypass grafts appear to be decreased and it is unclear how much benefit is gained over the use of a long prosthetic graft. Thus, if autogenous vein is compromised or unavailable in patients with critical limb ischemia, distal bypass with PTFE should be considered since it is still superior to a primary amputation. Another consideration includes a composite distal bypass using a proximal ePTFE graft joined to a patent popliteal segment with a venous segment extended to a tibial artery. However, the benefit of composite grafts over PTFE alone has not been proved. Cryopreserved vein and umbilical vein allografts may be used but their patency rates are no better than ePTFE bypasses. Other alternatives to autogenous vein are currently under investigation but there is no evidence to advocate their use over either autogenous vein or PTFE at this time.
Procedures may be performed under general, spinal or epidural anesthesia with adequate monitoring including an arterial line. Preoperative antibiotics are given 30 minutes prior to skin incision. Inflow and outflow vessels should be exposed, and the vein graft prepped, prior to anticoagulation and arterial clamping.
Surgical exposure varies depending on the target vessel and location of the distal anastomosis. The tibioperoneal trunk and proximal tibial vessels are exposed through a medial approach below the knee, avoiding injury to the greater saphenous vein during the skin incision. The muscular fascia is incised and the medial head of the gastrocnemius muscle is retracted posteriorly. If exposure is insufficient, the medial head of the gastrocnemius may be divided at the medial femoral condyle. The proximal tibial arteries are exposed by separation of the soleus muscle from the tibia. The mid-posterior tibial artery, the preferential target for distal bypass, runs between the tibialis posterior and the flexor digitorum longus muscles (Figure 2). Distally the posterior tibialis artery is exposed through a longitudinal incision posterior to the medial maleolus, splitting the distance between the malleolus and the Achilles tendon. The flexor retinaculum must be divided to expose the posterior tibial artery at this location. Exposure may be continued to the medial and lateral plantar arteries in the foot by continuing the dissection of the flexor retinaculum distally. The anterior tibial artery may be exposed along its length by an incision 2cm lateral to the tibia. The anterior tibial artery will be found by dividing the fascia overlying the anterior compartment and bluntly separating the tibialis anterior muscle and the flexor digitorum longus. The anterior tibial artery is usually associated with two overlying veins and the deep peroneal nerve. The dorsalis pedis artery is a continuation of the anterior tibial artery after crossing the ankle joint. This artery is exposed via a 2cm incision lateral to the extensor hallucis longus tendon on the dorsum of the foot. The peroneal artery may be exposed through a medial or lateral incision on the calf. A medial approach is best suited for access of the superior two-thirds of this vessel. The distal peroneal artery is exposed though a lateral incision over the fibula with excision of a segment of the fibula to revealing the underlying peroneal artery which is on the flexor hallucis longus muscle posterior to the intramuscular septum.
After target vessel exposure and vein harvest, intravenous heparin is given prior to arterial clamping at a dose of 70-100 units/kg and is re-dosed at 45 minute intervals as needed to maintain an activated clotting time (ACT) of 250-300. Gentle clamping techniques should be employed using atraumatic vascular clamps to minimize the possibility of clamp injury. Anastomoses are performed using small diameter (6-0 or 7-0) monofilament suture with good lighting and magnification. The proximal anastomosis is usually performed first. When using the non-reversed in-situ technique, the saphenous vein is left in place and the most proximal valve is lysed under direct vision while the remainder of the valves are lysed using a valvulotome after the proximal anastomosis is complete. Reversed saphenous vein bypasses are usually tunneled in the subcutaneous plane but may be tunneled in the deeper anatomic plane. Regardless of the plane chosen, attention must be paid to avoid graft twisting or kinking. A number of techniques can be used to enhance the distal anastomosis to improve outflow. The Linton patch enlarges the distal anastomosis by sewing a vein patch onto the tibial artery and then anastomosing the bypass graft onto the vein patch in an end-to-side fashion. Miller described a method of constructing a vein cuff secured to the distal target vessel thus allowing the bypass graft to be anastomosed to the vein cuff end-to-end. This method is particularly useful for prosthetic ePTFE tibial artery bypasses. The Taylor patch utilizes a vein patch to widen the distal graft anastomosis. Alternatively, Dardik has described creation of a side-to-side fistula between the distal target vessel and adjacent vein by opening both, sewing the back wall of the vein and artery together, and then anastomosing the vein graft to the anterior wall of both the artery and vein. These techniques should be considered when the tibial arteries are small and the outflow is poor with high arterial resistance.
After completion of the anastomoses and flow restoration, the adequacy of perfusion is assessed by inspection of the foot and toes, palpation of distal pulses and Doppler flow assessment in the bypass graft and outflow artery. We also perform intraoperative angiographic evaluation of the bypass and distal anastomosis to ensure there are no technical defects. Non-infected foot wounds greater than 2cm may be debrided at the end of the operation after arterial reconstruction. Debridement may include toe amputations which may be loosely closed. Skin grafts should be postponed until wounds are granulating.
The indications for endovascular interventions for tibioperoneal occlusive disease are similar to those for surgical bypass. Significant advances in imaging and endovascular technology and improved proficiency of interventionalists, have resulted in improved outcomes after peripheral vascular endovascular interventions. Although some advocate extending the indications to intervene earlier in the course of tibioperoneal disease, evidence suggests that infrapopliteal procedures should be reserved for limb salvage in appropriate candidates. Endovascular treatment of tibioperoneal disease for claudication should be avoided. Early intervention may place patients with underlying medical comorbidities at risk due to complications associated with intervention and early treatment failure. Unsuccessful endovascular treatment may result in worsening of symptoms and lead to critical limb ischemia and a potentially unsalvageable acute limb loss situation.
Despite the aforementioned concerns, the growing amentarium of endovascular options provide excellent alternatives for patients who are not suitable candidates for bypass. Patients with inadequate vein conduits or patients at high risk for bypass surgery may benefit from endovascular procedures with good limb salvage rates and low morbidity and mortality compared to open procedures. Endovascular procedures may also be used to temporize patients in preparation for bypass or supplement bypass procedures by augmenting inflow or outflow. These procedures may also allow for healing of ischemic ulcers and toe amputations with long-term limb salvage even if the endovascular intervention eventually fails. It is well known that limb salvage rates exceed the patency rates for endovascular interventions. During the past decade we have witnessed a dramatic increase in the number of endovascular treatments performed for lower extremity ischemia and this has been accompanied by a decrease in the overall major amputation rate.
Endovascular interventions are typically performed under epidural, spinal, or local anesthesia combined with sedation. Access for tibioperoneal disease may be obtained from the contralateral common femoral artery using a 5 or 6 French sheath. After diagnostic angiographic imaging, a cross-over sheath is advanced over the aortic bifurcation into the ipsilateral external iliac artery. A long guide sheath or a 6-French multipurpose catheter is introduced into the ipsilateral superficial femoral or popliteal artery providing support for infrapopliteal interventions. The cross-over technique is best suited for angiographic evaluation or treatment of short, straight stenoses. More advanced complex interventions to treat long stenoses, calcified lesions, or very distal lesions, may require antegrade access from the ipsilateral common femoral or popliteal artery. This approach allows more direct access for interventions and allows the operator to achieve maximal opacification of the distal circulation with less contrast.
Infrapopliteal interventions require high-resolution imaging. The use of low-osmolar contrast will be less painful in a patient under sedation and local anesthesia. Imaging of the trifurcation is usually obtained using a straight anterior-posterior view with a 4-Fr or 5-Fr diagnostic catheter. Additional views using a 30 degree ipsilateral oblique or a true lateral may better delineate the proximal anterior tibial artery and distal popliteal arteries.
Heparin is administered at the start of intervention at doses to maintain an ACT of 250-300 throughout the procedure. Most tibial interventions for stenotic lesions can be performed over a 0.014 inch guidewire. A 0.018 or 0.035 inch guidewire may be required for occlusive lesions. Catheter support can be used to traverse calcified or long lesions. On occasion, retrograde crossing of an occluded tibial artery can be achieved using a distal cutdown, followed by snaring and externalization of the wire from above, allowing antegrade performance of the remainder of the procedure.
Balloon angioplasty of stenotic lesions is the most common tibioperoneal endovascular intervention. Balloon angioplasty alone is most successful in the treatment of single, short segment stenoses (<1cm). Lesions less likely to respond to angioplasty include occlusive disease, long segment stenosis, multiple lesions and heavily calcified plaques. Stents may be used when the results of balloon angioplasty are subopotimal and stents are useful to correct abnormalities such as hemodynamically significant vessel recoil and arterial dissection. While the literature is inconsistent, the endovascular treatment of short segment stenoses has been reported to be successful in up to 98% of patients (Figure 3). More challenging lesions, such as occlusions, have a reported technical success rate nearing 80%. While long-term patency is uncertain, clinical resolution of symptoms exceed patency rates. Limb salvage, the ultimate goal of intervention, ranges from 50-84% at various intervals from 2-5 years.
Other endovascular treatment options include the use of cutting or scoring balloons, cryoplasty balloons, rotational athrectomy, and laser angioplasty. While early success with these technologies has been reported, the literature contains conflicting reports with anecdotal reports and limited long-term follow up. In our practice we have used cutting or scoring balloons for heavily calcified vessels with some success (Figure 4). Overall, results with rotational athrectomy appear disappointing but may be improved with use of GP IIb/IIIa inhibitors. Cryoplasty has shown little benefit over routine angioplasty and adjunctive stenting but investigation into the use of this technology in the tibial vessels is currently underway. Some encouraging results have been demonstrated with laser athrectomy but these reports are early.
Post-Intervention Treatment and Surveillance
Aspirin and ADP-receptor inhibitors should be continued after lower extremity endovascular interventions and should strongly be considered after distal bypass. The use of clopidogrel compared to aspirin alone has been demonstrated to decrease the incidence of vascular events in patients with peripheral artery disease. Antiplatelet drugs have further been shown to improve the patency of infrapopliteal grafts. Warfarin therapy should be considered in patients after bypass with prosthetic conduits since this may to improve patency rates, particularly in patients with failed previous bypass. Finally, statins should be considered for all patients unless contraindicated. In addition to the medical benefits of statins, recent trials indicate a cholesterol independent improvement in graft patency after bypass.
Surveillance of patients with saphenous vein bypass grafts should include duplex ultrasonography of the bypass along with measurement of ankle-brachial indices (ABIs) post-operatively, at one-month, 3-months, 6-months, 1-year and annually thereafter. Patients with prosthetic grafts are followed at similar time frames with the exception of biannual follow-up after one-year instead of annual follow-up. A decrease in ABI of 0.15 or greater, increased focal velocity at the anastomoses or within the bypass, or increases in mean graft velocity are suggestive of early graft failure and should prompt further imaging with CTA, MRA, or angiography.
Early failures after open interventions are usually the result of technical errors including vessel recoil, dissection and peri-procedural plaque embolization. Early failures may be prevented by intraoperative imaging and recognition of the defect before leaving the operating room. Most patients with early graft failure will require surgical re-intervention and reconstruction, typically with vein patch angioplasty. However, short segment stenoses of less than 1.5 cm may be amendable to percutaneous angioplasty provided the vein diameter is of adequate caliber (>3 cm).
Late failures are most often attributable to neointimal hyperplasia (1 month - 2 years) or progression of atherosclerotic disease (greater than 2years). These later failures are best treated with early recognition and re-intervention. Early re-intervention is often much simpler than the treatment required for complete thrombosis and is associated with improved long-term outcomes.
Patients treated with endovascular interventions should be followed with clinical examination, Duplex ultrasound imaging of the treated artery and ABIs. Re-intervention for these patients is reserved for recurrence of critical limb ischemia.
The management of tibioperoneal occlusive disease should be focused on the primary goal of limb salvage. Patients with claudication should be managed conservatively while patients with critical limb ischemia most often require intervention. Treatment options include tibial artery bypass and endovascular therapy. Good judgment is essential in patient and procedural selection, choice of operative and interventional techniques, post-operative surveillance and decisions for re-intervention. With optimal care the majority of patients can attain limb salvage, resulting in improved quality of life for the patient and overall cost savings for society.
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Figure 1 - Reversed Saphenous Vein Grafts. The wound morbidity associated with harvesting vein segments, which can be seen in up to 25% of patients, may be reduced by the use of skip incisions (A). Venous side branches are identified, ligated and transected during harvest. The vein is then flushed with heparinized saline clearing blood from the lumen and confirming ligation of all venous branches (B). The vein graft is soaked in papaverine solution until the surgeon is ready to tunnel the graft and begin the bypass (C).
Figure 2 – Exposure of the Posterior Tibial Artery.The posterior tibial artery is exposed at the mid-calf via a medial incision posterior to the tibia (A). The soleus muscle is retracted posteriorly (B). After tunneling the vein to the artery, the distal anastomosis completes the bypass (C).
Figure 3. Angioplasty of the posterior tibial artery.Angioplasty of the mid-posterior tibial artery (b) in a patient with critical limb ischemia (a) resulted in resolution of stenosis (c) and rest pain.
Figure 4. Angioplasty of the distal anterior tibial artery. Pre-angioplasty imaging reveals a 95% stenosis of the distal anterior tibial artery in a patient with critical limb ischemia (a). Angioplasty of this artery (b) resulted in less than 10% residual stenosis (c) and healing of ischemic foot ulceration.