The popliteal artery is a blood vessel situated behind the knee joint. Sometimes it weakens and expands like a balloon, known as an aneurysm. If left untreated, the blood clot within the aneurysm may migrate or the aneurysm may rupture or get blocked. Any of these complications can lead to limb loss or even death. Traditionally, popliteal artery aneurysm (PAA) has been treated surgically. However, it is also possible to treat the condition by a minimally invasive technique in which, a fabric lined metal mesh (stent graft), is placed across the aneurysm through a small puncture in the groin. The stent graft forms a seal within the artery. The success of the procedure is determined by the ability of the surgically applied graft or the stent graft to keep functioning and not get blocked (known as patency). Blockage of the graft decreases the leg circulation, which may require emergency surgery. Some consider the conventional surgical technique to be the gold standard, although the feasibility of the minimally invasive technique has been well documented in many studies where the data was analysed in retrospect. However, high quality evidence is only obtained when two techniques are pitted against each other in a clinical trial where data is collective prospectively, also known as a randomised clinical trial (RCT).
The purpose of this review was to combine the data from all the RCTs performed to date that compare the surgical technique versus the minimally invasive (endovascular) technique for the treatment of non-emergency PAA.
Study characteristics and key results
An extensive search of the medical literature databases was performed (current up to 29 January 2019). Only one completed RCT was found. In the published RCT, 30 PAAs were treated (15 by the endovascular technique and 15 by the surgical technique). Each case was followed up for a minimum of four years. In the group of participants treated using the endovascular technique there were two blockages. One case was re-stented and the other case required a surgical bypass. In the surgical group too, there were two blockages, which did not require any treatment. There were no limb losses. The time taken to complete the procedure and the length of hospital stay were shorter in the endovascular group. No information on wound complications was given in the trial report.
Reliability of the evidence
The major limitation of this study was that there were only 15 PAAs in each group so our certainty in the evidence is downgraded from high to moderate. Due to the limitations of the current evidence, we are unable to determine the effects of an endovascular stent graft versus conventional open surgery for the treatment of asymptomatic PAAs. A larger multicenter clinical trial is required so we can be more confident in the findings. We cannot say if there was a clear overall benefit on patency to either group (moderate-certainty evidence). As both operating time and hospital stay were reduced in the endovascular group (moderate certainty evidence), it may represent a viable alternative to open repair of PAA.
Evidence to determine the effectiveness of endovascular stent graft versus conventional open surgery for the treatment of asymptomatic PAAs is limited to data from one small study. At one year there is moderate-certainty evidence that primary patency may be improved in the surgery group but assisted primary patency rates were similar between groups. At four years there was no clear benefit from either endovascular stent graft or surgery to primary or assisted primary patency (moderate-certainty evidence). As both operating time and hospital stay were reduced in the endovascular group (moderate-certainty evidence), it may represent a viable alternative to open repair of PAA. A large multicenter RCT may provide more information in the future. However, difficulties in recruiting enough patients are likely, unless it is an international collaboration including a number of high volume vascular centres.
Popliteal artery aneurysm (PAA) is a focal dilatation and weakening of the popliteal artery. If left untreated, the aneurysm may thrombose, rupture or the clot within the aneurysm may embolise causing severe morbidity. PAA may be treated surgically by performing a bypass from the arterial segment proximal to the aneurysm to the arterial segment below the aneurysm, which excludes the aneurysm from the circulation. It may also be treated by a stent graft that is inserted percutaneously or through a small cut in the groin. The success of the procedure is gauged by the ability of the graft to stay patent over an extended duration. While surgical treatment is usually preferred in an emergency, the evidence on first line treatment in a non-emergency setting is unclear. This is an update of a review first published in 2014.
To assess the effectiveness of an endovascular stent graft versus conventional open surgery for the treatment of asymptomatic popliteal artery aneurysms (PAA) on primary and assisted patency rates, hospital stay, length of the procedure and local complications.
The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, CENTRAL, MEDLINE, Embase and CINAHL databases and World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registers to 29 January 2019.
We included all randomised controlled trials (RCTs) comparing endovascular stent grafting versus conventional open surgical repair in patients undergoing unilateral or bilateral prophylactic repair of asymptomatic PAAs.
We collected data on primary and assisted primary patency rates (primary endpoints) as well as operating time, the length of hospital stay, limb salvage and local wound complications (secondary endpoints). We presented results as risk ratio or mean difference with 95% confidence intervals and assessed the certainty of the evidence using GRADE.
No new studies were identified for this update. A single RCT with a total of 30 PAAs met the inclusion criteria. There was a low risk of selection bias and detection bias. However, the risks of performance bias, attrition bias and reporting bias were unclear from the study. Despite being an RCT, the certainty of the evidence was downgraded to moderate due to the small sample size, resulting in wide confidence intervals (CIs); only 30 PAAs were randomised over a period of five years (15 PAAs each in the groups receiving endovascular stent graft and undergoing conventional open surgery). The primary patency rate at one year was 93.3% in the endovascular group and 100% in the surgery group (RR 0.94, 95% CI 0.78 to 1.12; moderate-certainty evidence). The assisted patency rate at one year was similar in both groups (RR 1.00, 95% CI 0.88 to 1.13; moderate-certainty evidence). There was no clear evidence of a difference between the two groups in the primary or assisted patency rates at four years (13 grafts were patent from 15 PAA treatments in each group; RR 1.00, 95% CI 0.76 to 1.32; moderate-certainty evidence); the effects were imprecise and compatible with the benefit of either endovascular stent graft or surgery or no difference. Mean hospital stay was shorter in the endovascular group (4.3 days for the endovascular group versus 7.7 days for the surgical group; mean difference (MD) -3.40 days, 95% CI -4.42 to -2.38; P < 0.001; moderate-certainty evidence). Mean operating time was also reduced in the endovascular group (75.4 minutes in the endovascular group versus 195.3 minutes in the surgical group; MD -119.90 minutes, 95% CI -137.71 to -102.09; P < 0.001; moderate-certainty evidence). Limb salvage was 100% in both groups. Data on local wound complications were not published in the trial report.