Continuing Education Activity

Popliteal artery aneurysms are the most common aneurysms of the peripheral artery. They are true aneurysms, and their pathogenesis is related to the mechanical degradation of the tunica media by immune cells and the anatomic location of the popliteal artery at a high flexion point behind the knee. This activity reviews popliteal artery aneurysms, including anatomy, physiology, indications, and contraindications to repair. It goes over equipment and technique needed to perform both an open and endovascular repair. It also highlights the role of the interprofessional team in treating patients who undergo either open or endovascular popliteal artery aneurysm repair.

Objectives:

• Identify the indications for performing popliteal aneurysm repair.
• Describe the equipment, personnel, preparation, and technique in regards to popliteal aneurysm repair.
• Explain the appropriate evaluation of the potential complications and clinical significance of popliteal aneurysm repair.
• Review the interprofessional team strategies for improving care coordination and communication to advance popliteal artery aneurysm repair and improve outcomes.

Introduction

Popliteal artery aneurysms are the most common aneurysms of the peripheral artery, with 7/100,000 in men and 1/100,000 in women incidence.[1] They are true aneurysms, and their pathogenesis is related to the mechanical degradation of the tunica media by immune cells and the anatomic location of the popliteal artery at a high flexion point behind the knee.[2] The popliteal artery is aneurysmal if the vessel is 1.5 times the diameter of a normal adjacent segment of the artery.[3] Of patients with this pathology, 50% will have bilateral popliteal artery aneurysms, and 30 to 40% of these patients will have concomitant abdominal aortic aneurysms.[4] 

The growth rate of these aneurysms increases linearly as their diameter increases, and hypertension is the primary risk factor for increased growth.[1] Rupture is rare with these aneurysms, whereas distal ischemia from thrombosis or embolization is the most common cause of morbidity and results in a very high limb loss rate. Diagnosis can be made by physical examination with a prominent popliteal pulse and mass. Imaging including duplex ultrasonography, computed tomography angiography, magnetic resonance angiography, or standard angiography is useful in diagnosing these aneurysms.

Anatomy and Physiology

The popliteal artery is a superficial femoral artery continuation at the tendinous insertion of the adductor magnus muscle. It runs through the popliteal fossa and bifurcates into the anterior tibial artery and tibioperoneal trunk at the tibial tuberosity level.

Indications

Indications for popliteal artery aneurysm repair include:

• All symptomatic popliteal aneurysms should be repaired. Lower extremity ischemia is the most common presenting symptom, occurring secondary to embolization or thrombosis of the popliteal artery aneurysm.[5] Symptoms can range from claudication to acute limb ischemia. Less frequently, symptoms may arise secondary to compression from the aneurysm. This may lead to swelling or deep venous thrombosis from venous compression or nerve compression. Rupture is an unusual presentation, unlike other aneurysms.  
• Asymptomatic aneurysms that are more than 2 cm in diameter should be repaired in a healthy adult.[6]

Contraindications

Asymptomatic patients with a thrombosed popliteal artery aneurysm can be monitored for the progression of ischemic symptoms. Patients with poor tibial runoff may also be poor candidates for popliteal artery repair.[7]

Equipment

Open repair requires the following types of equipment:

• Operating room suite
• Personal protective equipment (mask, eye protection, bouffant, sterile gown, sterile gloves)
• Skin prep
• Sterile drapes
• Ultrasound
• Intravenous heparin
• Heparinized saline
• Electrocautery
• Standard vascular tray including scalpels (11 and 15 number blades), Castroviejo needle driver, tissue forceps, scissors, self-retaining retractors, vessel loops, bulldog clamps, and vascular clamps
• A combination of suture and ties per surgeon preference (silk, polyglactin, poliglecaprone, and polypropylene)
• Doppler to assess patency and flow intraoperatively

Equipment needed in endovascular repair are:

• Angiography suite including c-arm
• Dye injector with contrast
• Personal protective equipment (mask, eye protection, bouffant, sterile gown, sterile gloves)
• Skin prep
• Sterile drapes
• Ultrasound
• Intravenous heparin
• Heparinized saline
• Local anesthetic
• Micro puncture access kit
• Variety of arterial sheaths, catheters, and wires
• Flexible, self-expanding covered stent per surgeon preference
• Closure devise per surgeon preference

Personnel

Personnel needed in open repair are:

• Surgeon
• Anesthesiologist
• First Assistant
• Nursing staff (circulator and scrub tech)

Endovascular repair requires the following personnel:

• Surgeon
• Anesthesiologist
• First Assistant
• Nursing staff (circulator and scrub tech)
• Radiology technician

Preparation

Open surgical bypass and endovascular stent placement are both options in treating popliteal artery aneurysms, and there is an open-ended debate regarding which is preferred. A meta-analysis revealed that endovascular repair had lower wound complication rates and shorter length of stay than open repair; however, there was decreased primary patency at three years.[8] Endovascular stenting is more commonly used in elective patients with high perioperative risk for surgery, consistent with endovascular repairs in general. An individualized approach regarding patient presentation, medical comorbidities, anatomy, and the degree of ischemia is usually used.

Open Repair

As with any arterial reconstruction, case planning is paramount in achieving an optimal patient outcome. Preoperative imaging must be reviewed carefully to decide on proximal and distal anastomotic sites as well as the conduit. The anatomy and presentation are used to decide on the type of open approach used for repair. Most commonly used is the medial approach, which is best for small or fusiform aneurysms. Large or saccular aneurysms, especially if they cause compressive symptomatology, are best approached from a posterior approach.[9]

With regards to positioning, when using a medial approach, the patient is positioned supine. The patient is placed prone if using a posterior approach.

Endovascular Repair

The anatomy of the target vessel must be evaluated carefully. A landing zone of a minimum of 1.5 cm should be used proximal and distal to the aneurysm.[10] Severe kinking should also be avoided as it is likely to cause stent complications. Long-term patency of endovascular popliteal aneurysms relies significantly on outflow. One study revealed bypasses in extremities with adequate runoff had better patency (86%) than those in limbs with poor runoff (55%).[11] If the patient has only a single vessel runoff, this approach should be reconsidered. Patients will also need to be on dual antiplatelet therapy, which should be discussed before the endovascular intervention. 

About positioning, the patient is placed supine on a radiolucent angiography table.

Technique or Treatment

Open Repair, Medial Approach

An incision is made above the knee along the sartorius muscle's anterior border and below the knee just below the medial aspect of the tibia. The greater saphenous vein is harvested in the usual fashion. This is marked for later reversal and stored in heparinized saline. Attention is turned to the above-knee incision. The fascia between the adductor tendon superiorly and the sartorius muscle posteriorly is incised, and the popliteal fossa entered. A self-retaining retractor is placed, and the popliteal artery palpated. The artery is circumferentially dissected and isolated with vessel loops. Attention is then turned to exposure of the below-knee popliteal artery.

The soleus fascia is incised, and the soleus retracted superiorly, and the gastrocnemius retracted inferiorly with a self-retaining retractor. The below-knee popliteal artery is palpated and circumferentially dissected and isolated with vessel loops. A tunnel is created between the two heads of the gastrocnemius muscle. The patient is systemically heparinized to an active clotting time above 250 seconds. The vein is brought through the tunnel in a reversed fashion. Vascular clamps are applied to the proximal popliteal artery, and the distal artery is ligated as close to the aneurysm as possible. An end to end anastomosis is performed with a running 6-0 polypropylene suture.

The graft is flushed, and hemostasis is assured. The vascular clamp is then placed distal to the anastomosis. Vascular clamps are then placed to the below-knee popliteal artery, and the distal artery is ligated as close to the aneurysm as possible. An end to end anastomosis is performed with running 6-0 polypropylene suture. Before completing the anastomosis, the artery is back bled, forward bled and flushed with heparinized saline.

A doppler is brought onto the field, and flow is checked proximal and distal to the anastomosis and in the foot. Some providers open the aneurysm sac from above and below the knee and tie off any patent branch vessels present to prevent persistent flow into the sac despite exclusion. The wounds are irrigated and closed in multiple layers. Open Repair, Posterior Approach

An S-shaped incision is made starting on the thigh's medial side and extends along the flexion crease of the knee and ends on the lateral aspect of the calf. The small saphenous vein is examined and harvested if of adequate size. If not, the greater saphenous vein may be harvested from the thigh with the patient prone. This is marked for later reversal and stored in heparinized saline. Injury to the medial sural nerve should be avoided. The fascia is incised just medial to the small saphenous vein. The popliteal artery and vein will be deep and medial to the tibial nerve.

The popliteal vein must be carefully mobilized as it is directly posterior to the artery and swings to the posterolateral side. Dissection of the popliteal artery aneurysm is performed circumferentially to a healthy artery proximally and distally, and vessel loops are applied. The patient is systemically heparinized to an active clotting time above 250 seconds. Vascular clamps are applied proximally and distally, and the aneurysm sac opened on the anterior surface.

Bleeding vessels are oversewn. An interposition graft is performed with the reversed vein previously harvested like above. A doppler is brought onto the field, and flow is checked proximal and distal to the anastomosis and in the foot. The aneurysm sac is closed primarily over the graft. The wounds are irrigated and closed in multiple layers. Endovascular Repair

Common femoral access is obtained on the aneurysm's contralateral side (retrograde access) using a micropuncture needle under ultrasound guidance. This is upsized to a small sheath and a standard aortoiliac angiogram obtained with a wire and flush catheter. The ipsilateral superficial femoral artery is selected, and an appropriately sized sheath is placed, ending in the common femoral artery. A dedicated angiogram is obtained of the popliteal aneurysm, proximal and distal landing zones, as well as the runoff to the foot.

The patient is systemically heparinized to an active clotting time above 250 seconds. The popliteal artery aneurysm is carefully crossed with a soft wire (e.g., glidewire), and a catheter is placed distal to the aneurysm in a tibial runoff vessel. A stiff wire is placed through this catheter, and the stent-graft is deployed in the standard fashion over this wire. Care is taken to achieve adequate proximal and distal seal zones with no coverage of tibial branches.

Appropriately sized balloons are used to ensure an adequate seal. With and without the knee bent, repeated angiogram confirms placement of the stent-graft and distal outflow to the foot. Protamine may be given for reversal, and the sheath is removed with the aid of a closure device per surgeon preference. The pressure is held, and hemostasis is achieved.

Complications

Open Repair

Complications of open popliteal artery aneurysm repair either by medial or posterior approach include:

• Wound complications
• Sac expansion
• Vein graft aneurysm
• Graft failure[12]

Endovascular Repair

Complications of popliteal artery stenting are similar to other peripheral artery stents. These include:

• Access site complications (including hematoma, pseudoaneurysm)
• Stent kinking, migration, fracture, thrombosis, or endoleak[13]

Clinical Significance

Popliteal artery aneurysms, although rare, may put the affected limb at risk. Any symptomatic aneurysm, or one larger than 2 cm, should be considered for repair as above. Endovascular repair has been shown to decrease the length of stay and wound complications; however, its durability is inferior. The decision regarding open or endovascular repair should be individualized, and the risks and benefits of each should be discussed with the patient.

Enhancing Healthcare Team Outcomes

Successful popliteal aneurysm repair requires an interprofessional effort by the healthcare team. Whether it be an open repair or endovascular, a collaborative approach must be used to optimize patient outcomes. Anesthesiologists, registered nurses, scrub technologists, and radiology technologists with specialized skills are essential for optimal repair.