Early and mid-term results in the endovascular treatment of popliteal aneurysms with the multilayer flow modulator

Abstract

Background

The endovascular approach became an alternative to open surgical treatment of popliteal artery aneurysm over the last few years. Heparin-bonded stent-grafts have been employed for endovascular popliteal artery aneurysm repair, showing good and stable results. Only few reports about the use of multilayer flow modulator are available in literature, providing small patient series and short follow-up. The aim of this study is to report the outcomes of patients with popliteal artery aneurysm treated with the multilayer flow modulator in three Italian centres.

Methods

We retrospectively analysed a series of both symptomatic and asymptomatic patients with popliteal artery aneurysm treated with the multilayer flow modulator from 2009 to 2015. Follow-up was undertaken with clinical and contrast-enhanced ultrasound examinations at 1, 6 and 12 months, and yearly thereafter. Computed tomography angiography was performed in selected cases. Primary endpoints were aneurysm sac thrombosis; freedom from sac enlargement and primary, primary-assisted and secondary patency during follow-up. Secondary endpoints were technical success, collateral vessels patency, limb salvage and aneurysm-related complications.

Results

Twenty-three consecutive patients (19 males, age 72 ± 11) with 25 popliteal artery aneurysms (mean diameter 23 mm ± 1, 3 symptomatic patients) were treated with 40 multilayer flow modulators during the period of the study. Median follow-up was 22.6 ± 16.7 months. Complete aneurysm thrombosis occurred in 92.9% of cases (23/25 cases) at 18 months. Freedom from sac enlargement was 100% (25/25 cases) with 17 cases of aneurysm sac shrinkage (68%). At 1, 6, 12 and 24 months, estimated primary patency was 95.7%, 87.3%, 77% and 70.1%, respectively. At the same intervals, primary-assisted patency was 95.7%, 91.3%, 86% and 86%, respectively, and secondary patency was 100%, 95.7%, 90.3% and 90.3%, respectively. Technical success was 100%. The collateral vessels patency was 72.4%. Limb salvage was 91.4% at 24-month follow-up. One multilayer flow modulator fracture was reported in an asymptomatic patient.

Conclusions

Multilayer flow modulator seems a feasible and safe solution for endovascular treatment of popliteal artery aneurysms in selected patients.

Keywords

Endovascular popliteal artery aneurysm Cardiatis multilayer flow modulator endovascular popliteal artery aneurysm repair

Introduction

A popliteal aneurysm is defined as an arterial dilatation of at least 1.5 times the diameter of the native blood vessel or with an external diameter ≥20 mm.¹ Popliteal artery aneurysm (PAA) is the second most frequent arterial aneurysm localization, accounting for about 70% of all peripheral aneurysms.² The possible complications are limb loss due to thrombosis of the aneurysmal sac (from 15% to 59%),^3,4 limb ischaemia caused by distal embolization through the run-off vessels and bleeding due to rupture. Treatment is suggested for symptomatic patients and for asymptomatic patients with aneurysm diameter >20 mm.⁵

The gold standard for the PAA treatment is surgical repair with aneurysmal sac ligation or resection, followed by venous or prosthetic bypass grafting.^6,7 Endovascular popliteal artery aneurysm repair (EPAR) is a good alternative treatment for the patients affected by severe comorbidities, allowing shorter hospital stay, less post-operative complications and comparable short- and mid-term patency rates.^8,9

EPAR is mostly performed with new heparin-bonded stent-graft.^8,10 The multilayer flow modulator (MFM) has been rarely employed for the treatment of PAAs and only few experiences are reported.^11,12

The aim of this study is to present the results of a three-centre experience in the endovascular treatment of PAA using MFM.

Material and methods

Study design

All patients with asymptomatic or symptomatic PAA treated with MFM in three Italian centres between September 2009 and December 2015 were considered for this study. Cases performed after this period were not included in the study in order to have a sufficient follow-up for the evaluation of endpoints. EPAR with MFM was considered for PAA with >20 mm diameter in asymptomatic patients and independent of the diameter in symptomatic patients. Patients at high surgical risk with healthy proximal and distal neck of at least 10 mm in length were treated with MFM. Patients with inadequate arterial access, inadequate proximal and distal neck, ruptured aneurysm, contraindications to both anti-platelet and anticoagulant drugs and previous endovascular stent-graft implant in the popliteal segment were excluded for the treatment with MFM.¹³

Data collection

Patients’ data were collected and retrospectively analysed. Demographic collected data were age and sex. Comorbidities data included hypertension (defined as blood pressure >140/90 mmHg or need of anti-hypertensive drugs for blood pressure control), hyperlipidaemia (blood total cholesterol >200 mg/dl), diabetes mellitus (need of hypoglycaemic therapy to maintain glycaemic control), coronary artery disease (history of myocardial infarction or previous surgical or endovascular coronary revascularization), chronic obstructive pulmonary disease (COPD, defined as FEV1 <70%), renal failure (glomerular filtration rate <60 ml/h estimated with MDRD),¹⁴ smoking history (active or former smoker), obesity (BMI > 30) and American Society of Anesthesiologist Physical Status Classification (ASA). The clinical presentation was recorded (symptomatic and asymptomatic patient). Anatomical data collected were aneurysm diameter, arterial run-in, run-off patent vessels, diameter and length of proximal and distal sealing zone, presence of a contralateral popliteal aneurysm and other aneurysm localization and number of collateral vessels originating from the aneurysm sac. Procedural data collected were type of anaesthesia, surgical or percutaneous approach to common femoral artery, previous need of intrarterial fibrinolysis, number of MFM employed for each procedure, diameter and length of each device, number of patent collateral vessels covered during the procedure and number of collateral vessels patent at the end of the procedure, need for adjunctive procedure (e.g. transluminal angioplasty of superficial femoral artery or run-off vessels), intraoperative heparin bolus and anticoagulant and antiplatelet medical therapy prescribed after the procedure. Data considered for early results were technical success, length of hospital stay, need of surgical or endovascular adjunctive procedure at 30 days and any MFM-related complications at 30 days. Follow-up was based on the clinical assessment and contrast-enhanced ultrasound (CEUS) at 1, 6 and 12 months and yearly thereafter. Computed tomography angiography (CTA) was performed only in case of incomplete aneurysm thrombosis at Doppler ultrasound (DUS) analysis. In these cases, both arterial and venous phases were analysed. The collected follow-up data were complication or need of reintervention after 30 days, type of follow-up (CEUS or CTA), primary, primary-assisted and secondary patency, diameter and thrombosis of aneurysm sac, patent run-off vessels and patent collateral vessels, limb salvage, and MFM-related complications after 30 days.

Treatment

A DUS was performed to diagnose the aneurysm and to define the arterial in-flow and out-flow, and a CTA was performed in all cases for preoperative planning. In case of haemodynamic stenosis above the popliteal artery, a transluminal angioplasty was performed before MFM deployment. A 10-mm length of proximal and distal sealing zone was requested for treatment, according to Instructions for Use.¹³ The common femoral artery access was obtained with percutaneous or surgical ipsilateral approach, according to the operator’s preference combined with DUS analysis. During the procedure, an intravenous bolus of heparin (5000 UI) was administered in all patients. The procedure was performed in the operating theatre with a mobile c-arm or in the angiography suite using fixed c-arm. During the procedure, one or more MFMs were deployed. The overlap between two stents was at least 20 mm.¹³

Multiple intraoperative digital subtraction angiographies were performed (in extension and flexion of the knee) to check the stent placement and the patency of outflow vessels. In cases of percutaneous approach, haemostasis was obtained with manual compression if the device was 6 Fr or 7 Fr compatible. If a larger introducer sheath was necessary, a closure system was used (Perclose Proglide ® – Abbott Vascular Inc., Santa Clara, CA). A dual antiplatelet therapy was administered for at least one month in all cases, except for patients who required oral anticoagulation for other reasons. After this period, a single antiplatelet therapy was continued for life.

Early results

Technical success, length of hospital stay and need of reintervention or other MFM-related complications at 30 days from the treatment were considered as early results.

Technical success was defined as successful stent deployment with no intraoperative complications or stent defects.

Other MFM-related complications were defined as early MFM occlusion, MFM fracture or migration within 30 days.

Endpoints

Primary endpoints were early and late aneurysm sac thrombosis; freedom from aneurysm sac enlargement; and primary, primary-assisted and secondary MFM patency.

Secondary endpoints were collateral patent vessels, limb salvage and MFM-related complications during the follow-up.

The aneurysm sac thrombosis was defined as the absence of contrast medium in the aneurysm sac at the CEUS or CTA control. The primary patency was defined as blood flow persistence through the device after deployment without any intervention required. The primary-assisted patency was defined as persistent blood flow through the device after deployment, regardless of reinterventions performed. The secondary patency was defined as the persistence of blood flow through the device regardless of reinterventions performed after total occlusion.¹⁵ The limb salvage was considered when no major amputations were reported. MFM-related complications were defined as symptomatic run-off vessels embolization, bleeding due to aneurysm rupture or anatomical compression of other structures and MFM migration or fracture after 30 days from treatment.

Statistical analysis

Quantitative data are presented as mean ± standard deviation, while categorical data are given as counts and percentage. Primary, primary-assisted, secondary patency, limb salvage and aneurysm sac thrombosis were estimated using Kaplan–Meier analysis. The threshold for statistical significance was P < 0.05. All statistical analyses were performed using SPSS software (version 13.0; SPSS Inc., Chicago, IL).

Results

Population

Twenty-three patients, 19 male (82.6%) with a mean age of 72 years ± 11, were treated for 25 PAA (two patients bilaterally treated) with MFM in the three centres. Twenty-two cases (88%) were treated for asymptomatic PAA and three cases (12%) for symptomatic aneurysms (two acute limb ischaemia for aneurysm thrombosis and one distal embolization). The patients’ demographics and comorbidities are described in Table 1.

Table 1.

Patients demographics and comorbidities (N = 23).

	N (%)
Bilateral treated patients	2 (8.7)
Male gender	19 (82.6)
Mean age (years ± standard deviation)	72 ± 11
Diabetes mellitus	1 (4.3)
Hypertension	19 (82.6)
Hyperlipidaemia	10 (43.5)
Coronary artery disease	4 (17.4)
Chronic obstructive pulmonary disease	7 (30.4)
Active smoker	4 (17.4)
Former smoker	9 (39.1)
Obesity (BMI > 30)	5 (21.7)
Renal failure	3 (13)
ASA 3	19 (76)
ASA 4	6 (24)

ASA: American Society of Anesthesiologist Physical Status Classification.

The mean aneurysm diameter was 23 mm ± 1. One patient (4%) presented an aneurysm involving the distal segment of superficial femoral artery. Aneurysms characteristics are described in Table 2.

Table 2.

Aneurysms characteristics (N = 25 cases).

	N (%)
Symptomatic patient	3(12)
Mean diameter (mm)	23±1
Ø between 20 and 25 mm	9 (36)
Ø between 26 and 30 mm	6 (24)
Ø ≥ 30mm	10 (40)
0–1 patent run-off vessel	5 (20)
2–3 patent run-off vessels	20 (80)

Procedure and post-operative period

The femoral access was performed through local anaesthesia and percutaneous approach in 11 cases (44%) and spinal anaesthesia and surgical approach in 14 cases (56%), respectively.

All three symptomatic patients (12%) underwent intrarterial fibrinolysis (initial bolus of 100,000 UI of Urokinase and intrarterial infusion of 75,000 UI/h for a maximum of 72 h) before MFM deployment with complete restoration of distal vessels patency in two cases. The number of MFM deployed for each procedure is shown in Table 3.

Table 3.

Number of MFM deployed for procedures.

Number of stent	N (%)
1	16 (64)
2	6 (24)
3	2 (4)
4	1 (2)

MFM: multilayer flow modulator.

Data regarding collateral side branches were available in 10 cases. In the analysed cases, 29 collateral side branches were covered during the procedure. The mean number of covered branches was 2.4.

In three elective cases (12%), adjunctive procedures were performed: one patient underwent superficial femoral artery transluminal angioplasty before stent deployment for a haemodynamic stenosis, one patient was treated after stent deployment with posterior tibial artery transluminal angioplasty and one patient with a 22-mm aneurysm of superficial femoral artery was treated with MFM after MFM deployment in the popliteal segment.

Dual antiplatelet therapy was administered in 7 (28%) cases for three months after the procedure and in 13 cases (52%) for one month after stent deployment according to the centre protocols. Four patients (16%) received Coumarin derivate alone because of atrial fibrillation or previous deep vein thrombosis and one patient (4%) received only acetylsalicylic acid and Light Molecular Weight Heparin for one month because of dual antiplatelet therapy contraindication due to previous brain haemorrhage.

Early results

Technical success was 100%. The mean hospital stay was 4 days ± 3.2. The surgical or endovascular reintervention rate within 30 days was 8.6%. One MFM complete thrombosis was observed during the first 30 days, which was successfully treated with intrarterial fibrinolysis. The patient declared no antiplatelet drug assumption as prescribed.

One major amputation was performed in the first 30 days.

The patient originally presented with massive acute limb ischaemia due to a distal run-off vessel embolization. After intrarterial fibrinolysis, an MFM was deployed to prevent new embolic event, but it was impossible to restore the run-off vessels patency and, after gangrene progression, a leg amputation was needed.

No MFM-related complications were reported in the perioperative period.

Endpoints

The mean follow-up was 22.6 months ±16.8. The aneurysm sac thrombosis was observed in 92.9% at 1, 6, 12 and 24 months (Figure 1). The freedom from sac enlargement was seen in 25 cases (100%) with aneurysm sac shrinkage observed in 17 cases (68%). All patients with sac shrinkage had complete aneurysm thrombosis.

Figure 1.

Estimated aneurysm sac thrombosis rate.

At 1, 6, 12 and 24 months, estimated primary patency was 95.7%, 87.3%, 77% and 70.1%, respectively (Figure 2). Three intra-stent stenosis and four occlusions occurred during follow-up period.

Figure 2.

Estimated primary patency. Blue line shows standard error > to 10%.

At the same intervals, primary-assisted patency was 95.7%, 91.3%, 86% and 86%, respectively (Figure 3). Three intra-stent stenosis were treated with intraluminal angioplasty. Two of these patients presented with late (32 and 24 months) occlusion, and a femoro-popliteal bypass was performed in both cases.

Figure 3.

Estimated primary-assisted patency. Blue line shows standard error > to 10%

At 1, 6, 12 and 24 months, secondary patency was 100%, 95.7%, 90.3% and 90.3%, respectively (Figure 4).

Figure 4.

Estimated secondary patency.

The patency rate of the collateral side branches was 72.4% (eight collateral vessels occluded during the follow-up). At 1, 6, 12 and 24 months, the limb salvage was 96%, 91.4%, 91.4% and 91.4%, respectively (Figure 5). One major amputation was necessary during the follow-up. The patient presented with acute limb ischaemia due to MFM occlusion. Following an unsuccessful femoro-popliteal bypass that was performed in an urgent setting, a major amputation was performed on fourth post-operative day.

Figure 5.

Estimated limb salvage.

The rate of MFM-related complications was 4%. One MFM minimal fracture was occasionally reported at 20 months from the procedure. The patient was asymptomatic for limb claudication and the aneurysm was completely excluded. An ultrasound analysis showed regular flow in the popliteal artery below the MFM. No further procedures were performed, and the patient continued the follow-up without any complications.

Discussion

To our best knowledge, this study provides the largest case series ever published in literature dealing with follow-up outcomes of MFM in the popliteal district. The mean follow-up is comparable to other experiences with EPAR in literature.^16,17 The endovascular treatment of PAA with MFM demonstrated to be a feasible procedure. At 2-year follow-up, primary patency was maintained in 70% of cases with limb salvage >90%. In our series, reintervention was necessary in about a quarter of cases, and the correction was mostly possible by endovascular means (six reinterventions, 24%). The most frequent complication is stent thrombosis.

The open surgical repair (OR) of popliteal aneurysms is still considered the gold standard for this limb-threatening disease. Dorigo et al.¹⁸ reported their experience in 234 consecutive cases of surgical treatment of PAA. In this experience, an estimated primary and secondary patency of 55.1% and 68.1%, respectively, was observed during 13 years with limb salvage rate during the same period as 86%.¹⁸ Ravn et al.,⁶ in their series of 717 symptomatic and asymptomatic popliteal aneurysms, experienced a primary patency of 90% at one-year follow-up when a vein graft was used for a medial approach and 85% if the same graft was used for the posterior approach. When prosthetic graft was used, primary patency at one-year follow-up was 81% for the posterior approach and 72% for the medial approach.⁶ Other experiences have been reported in literature supporting optimal results of surgical repair in terms of mid- and long-term patency and limb salvage, especially in asymptomatic patients.³

Many experiences tried to determine the real role of endovascular technique in popliteal artery treatment, comparing EPAR with OR for PAAs.^19,20

Joshi et al.²¹ reported comparable results between EPAR and surgical treatment in terms of patency (86.6% both endovascular and surgical group) and amputation rate (0% for both groups) during a four-year follow-up, with shorter operative time (75.4 min for endovascular groups vs. 195.3 for surgical group, P < 0.001) and hospital stay (4.3 days vs. 7.7 days, P < 0.001) in endovascular group.²¹ Galinanes et al.²² reported 2962 cases of popliteal aneurysm treated both with surgical approach and EPAR. No differences were found in term of mortality, amputation rate and hospital readmission at 90 days. Although EPAR was associated with a shorter hospital stay, this group was characterized by higher hospital charges.²²

In a meta-analysis published in 2017 by Leake et al.,²³ OR resulted superior to EPAR in terms of primary patency and reintervention rate at one and three years. Although these two techniques had no differences in terms of secondary patency, patients treated with EPAR showed lower hospital stays and lower wound complications.²³

Heparin-bonded stent-graft has been widely used over the last few years in EPAR, becoming the first choice material for this technique.

Pulli et al.¹⁰ reported 134 popliteal aneurysms treated with heparin-bonded stent-graft experiencing a primary patency rate at 12 and 24 months of 79.1% and 77.9%, respectively; a secondary patency rate at the same intervals of 90.8% and 85.5%; and limb salvage rate at 24 months of 96.9%.¹⁰ Also, Golchehr et al.⁸ reported their experience (72 cases) in EPAR with heparin-bonded stent-graft, with a median follow-up of 13 months (range 0–63 months). A primary patency of 86% at one year and 69% at two and three years was reported. Secondary patency at one, two and three years was 88%, 81% and 76%, respectively, with a limb salvage rate of 100% (no major amputations during entire follow-up).⁸ Many other authors reported good and stable results in EPAR with heparin-bonded stent-graft with comparable follow-up.^24,25

Only few experiences using the MFM in EPAR are described. Thakar et al.¹¹ experienced EPAR with MFM in six cases, reporting a 50% stent thrombosis, with a mean follow-up of 5.8 months (range 3–12 months). This study was limited by the small number of patients and the low rate of dual antiplatelet therapy assumption by the patients.¹¹ Ruffino et al.¹² reported six cases of popliteal aneurysms in the experience of “Italian registry in Cardiatis® multilayer stent deployment for the treatment of visceral and peripheral aneurysms.” For popliteal district, no stent occlusion during 12-month follow-up was reported with 100% sac thrombosis rate during the same period. Only one case presented type III endoleak due to Cardiatis® shortening at three months.¹² Antoniou et al.²⁶ reported their experience in six cases of EPAR using the MFM experiencing 67% primary patency and 100% secondary patency at six months. In all cases, partial or complete thrombosis of the aneurysm sac was observed.²⁶

In our experience, primary, primary-assisted and secondary patency at 24 months was 70.1%, 86% and 90.3%, respectively. There were two major amputations during the entire follow-up with a limb salvage rate of 91.4%. These results are comparable with heparin-bonded stent-graft experiences previously reported.^8,10 Only one case of MFM fracture was reported in asymptomatic patient. This is probably due to the three-dimensional structure and the material used for MFM, making this device really flexible and appropriate for popliteal district.

An important aspect of MFM is the concept of “flow modulation” through the aneurysms sac. With this multilayer laminated structure, MFM does not exclude the aneurysm from the blood flow like other devices but laminate the blood flow through the aneurysm sac allowing progressive thrombus apposition into the aneurysm sac, maintaining the collateral vessels patency.²⁷

In our series, aneurysms sac thrombosis rate was 92.9%, with aneurysms sac shrinkage in 68% (17 cases) of cases and stable aneurysms diameter in 100% of cases. No statistical differences were observed in patients receiving dual antiplatelet therapy or anticoagulant drugs in terms of aneurysm sac thrombosis (P = 0.78).

One of the main characteristics of MFM, making this device unique with respect to covered stent-graft or surgical treatment, is to maintain collateral vessels patency originating from the aneurysm sac after stent deployment. These data were available for 10 patients in our series, with a patency rate of 72.4%. No statistical differences were observed in terms of collateral vessels patency between patients receiving dual antiplatelet therapy and patient receiving anticoagulant drugs (P = 0.68). To date, no specific data regarding collateral vessels patency in popliteal aneurysm are reported in literature.

The potential limitations of this study are due to retrospective analysis, small sample of patients, short mean follow-up, incomplete standardized procedure, limits of CEUS both for EPAR follow-up and collateral vessels detection originating from the aneurysm sac and difference in antiplatelet drugs prescription between the centres.

Conclusions

EPAR with MFM demonstrated to be a feasible and safe alternative to OR in selected patient. The follow-up patency is comparable with covered stent-grafts, and the low rate of distal embolization is associated with good limb salvage rates. Further studies with larger patient samples are needed in order to assess the real role of this device in EPAR.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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