Abstract
Background
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.
Objectives
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.
Search methods
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.
Selection criteria
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.
Data collection and analysis
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.
Main results
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.
Authors' conclusions
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.
Plain language summary
Minimally invasive versus surgical treatment of an aneurysm of the popliteal artery
Background
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.
Summary of findings
Summary of findings for the main comparison. Treatment of asymptomatic popliteal artery aneurysms with endovascular stent graft.
| Endovascular stent graft treatment compared with surgical treatment for asymptomatic PAA | ||||||
|
Patient or population: patients older than 50 years with asymptomatic PAA Settings: hospital (non‐emergency) Intervention: endovascular treatment Comparison: open surgical treatment | ||||||
| Outcomes | Anticipated absolute effects* (95% CI) | Relative effect (95% CI) | No of PAA (RCTs) | Certainty of the evidence (GRADE) | Comments | |
| Risk with open surgical treatment | Risk with endovascular treatment | |||||
|
Primary patency rate at 4 yearsa |
Low risk populationb | RR 1.00 (0.76 to 1.32) | 30 (1) | ⊕⊕⊕⊝ moderatec | Although, the long‐term follow‐up data were available there was a limited number of cases: two occlusions in each group | |
| 867 per 1000 | 867 per 1000 (659 to 1000) | |||||
| Assisted primary patency rate at 4 years | Low risk population | RR 1.00 (0.76 to 1.32) | 30 (1) | ⊕⊕⊕⊝ moderatec | Although, the long‐term follow‐up data were available there was a limited number of cases | |
| 867 per 1000 | 867 per 1000 (659 to 1000) | |||||
|
Hospital stay in days |
The mean hospital stay was 7.7 days | The mean hospital stay was 3.4 days less (4.4 days less to 2.4 days less) | ‐ | 30 (1) | ⊕⊕⊕⊝ moderatec | Favours endovascular repair |
|
Operating time in mins |
The mean operating time was 195.3 mins | The mean operating time was 119.9 mins less (137.7 mins less to 102 mins less) | ‐ | 30 (1) | ⊕⊕⊕⊝ moderatec | Favours endovascular repair |
| *The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; mins: minutes; PAA: popliteal artery aneurysm;RCTs: randomised controlled trials;RR: risk ratio. | ||||||
| GRADE Working Group grades of evidence High certainty: We are very confident that the true effect lies close to that of the estimate of the effect Moderate certainty: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different Low certainty: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect Very low certainty: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect | ||||||
a The risk of an occlusion is an inverse event with respect to the primary outcome of patency. The occluded grafts are equal to the total procedures minus the number of grafts/stent grafts patent at 4 years b The cases were all elective non‐emergency repairs, hence only a low risk population has been classified. A separate operative risk subgroup was not published in the included review c The evidence has been downgraded to 'moderate' for each of the outcomes because there was a limited number of participants available for comparison, this has led to widening of the CI (imprecision)
Background
Description of the condition
An aneurysm is defined as a localised dilatation of the arterial wall. The popliteal artery is considered aneurysmal when it is more than 1.5 times the diameter of the adjacent normal arterial segment (Callum 1974). Popliteal artery aneurysm (PAA) accounts for 70% of all peripheral arterial aneurysms, although aneurysms of the aorta are more common (Szilagyi 1981). The overall incidence of PAAs is 0.1% and about half of these cases have bilateral disease and an association with aortic or femoral aneurysms (Dawson 1991; Dawson 1997). Males between the age of 60 and 70 years are most commonly affected by PAA. The incidence of PAA in females is extremely rare. In a retrospective study of 485 patients undergoing PAA treatment in a single institution over 28 years, only 8 (1.6%) were females (Peeran 2016). The precise etiopathogenesis is unknown, however, it is likely to be a combination of atherosclerosis, proteolytic vessel wall degradation, genetic predisposition and mechanical stress (Dawson 1997). Increasing numbers of PAA are now recognized at an asymptomatic stage, either incidentally or in screening programmes that are aimed at detecting abdominal aortic aneurysms (Björck 2014; Wright 2004). A common complication of PAA is chronic limb ischaemia, which occurs secondarily to distal embolisation of fragments of thrombus contained within the sac of the aneurysm. Acute limb ischaemia may also result from sudden thrombotic occlusion or rupture of the aneurysm sac. Indirect symptoms may be caused by compression of the popliteal vein or the sciatic nerve, leading to leg oedema and pain respectively (Lowell 1994).
Ischaemic complications occur in up to 45% of people with PAA, and major amputation (above the ankle) in 4% of those patients (Roggo 1993). However, major amputation rates that are as high as 48% have been reported (Gifford 1953). Hence prophylactic treatment of PAA is indicated when the aneurysm sac measures more than 2 to 3 cm. The need is greater if significant thrombotic load or occlusion of the tibial arteries (anterior tibial, posterior tibial and peroneal arteries) from chronic thromboembolism (Galland 2008).
Description of the intervention
The treatment of PAA has evolved considerably over the years. Currently the two main techniques are the conventional open surgical approach and covered endoluminal stent graft repair. The surgical repair of PAA involves ligation of the popliteal artery both above and below the PAA and bypassing the excluded segment using either a prosthetic graft or a reversed autologous vein graft. The latter technique is generally preferred (Huang 2007). This allows exclusion of the aneurysm from the limb circulation and provides adequate revascularisation. The site of the proximal and the distal anastomoses of the bypass conduit varies with the quality of the non‐aneurysmal popliteal artery and the superficial femoral artery below and above the aneurysm respectively. Sometimes the proximal anastomosis may have to be made on the common femoral artery in the groin and the tibio‐peroneal trunk below the knee. More distal anastomoses are rare, except in symptomatic aneurysms. An alternative surgical technique is aneurysmotomy or aneurysmectomy followed by transposition of a tubular prosthetic graft between the proximal and distal normal segments of the popliteal artery. The latter technique is similar to abdominal aortic aneurysm surgery, however the former approach is more common (Wain 2007).
Marin et al first described endovascular repair of PAAs in 1994 (Marin 1994). It is usually performed percutaneously or via small incision in the groin to access the ipsilateral common femoral artery. A covered stent graft is deployed within the lumen of the PAA under radiological guidance. A seal is formed at the proximal and the distal landing zones (non‐aneurysmal artery where the proximal and distal ends of the graft rest). This helps in excluding the aneurysm sac from the circulation (Cina 2010). Occasionally, the landing zones may not be adequate, due to the sural branches emanating from the main popliteal artery. Embolisation of these branches may be required prior to deployment of the main stent graft to avoid blood leaking back into the sac, from reverse flow in the branches (type‐2 endoleak). The length of the parallel walled landing zones above and below the aneurysm and the lack of mismatch in size between these two landing zones determine the anatomical suitability for endovascular repair. If adequate landing zones are not attained, either a primary surgical approach or conversion to the conventional surgical approach may be necessary (Antonello 2005a).
How the intervention might work
While successful repair of PAA is possible by both the endovascular and open surgical approaches, there is no consensus on the preferred technique in the various clinical settings. Both techniques are able to exclude the thrombus that is inside the aneurysm from the limb circulation, hence removing the possibility of sudden rupture and distal embolisation of the fragments of thrombus. For a patient with an aneurysm presenting with symptoms including acute ischaemia and those resulting from pressure, conventional surgical treatment is generally preferred (Hupalo 2009), although some reports have indicated that endovascular repair is feasible in some cases (Gerasimidis 2003). For asymptomatic aneurysms the choice of technique often reflects the available local resources, including expertise.
Unfortunately most grafts, whether prosthetic, native or endoluminal, eventually get blocked. The durability of the graft varies but many factors interplay to determine the longevity. These include the graft material, patient factors and medication such as antiplatelet therapy.
Many proprietary covered stent grafts are available for this procedure (Beregi 1999; Kudelko 1998; Tielliu 2010). Most of them are based on the same principle, a self‐expanding tubular mesh made out of a malleable metal alloy and lined with a thin synthetic membrane (such as polytetrafluoroethylene (PTFE)) that simulates the endothelium of the native artery. Recently, a multilayer flow modulator stent (without any fabric lining) has also been successfully tested in 19 patients (Ucci 2018). This works by flow diversion and eventual spontaneous thrombosis of the extraluminal aneurysm sac, a principle that is commonly used to treat wide‐necked cerebral aneurysms. Therefore, it is possible that with further improvements in the elastic properties of the metal alloys and the overall design of stent grafts, the tribulations of stent fracture and kinking will be overcome.
Why it is important to do this review
There is no clear consensus on the treatment of PAA. The proponents of the open surgical technique argue that surgical repair offers better long‐term patency rates of the bypass conduit. A North American case series that consisted of a large cohort of patients undergoing PAA repair (583 open operations in 537 patients) showed a limb salvage rate of 99% at 30 days, 97.6% at 1 year, and 96.2% at 2 years (Johnson 2008). However, consistent developments in stent graft technology and the relative success of endovascular aortic aneurysm repair have inspired the increasing popularity of endovascular treatment of PAA. Nevertheless, compared to the aorta the popliteal artery is much smaller and is subject to greater external mechanical stress from frequent movement at the knee joint. This increases the risk of stent kinking, fracture or migration, which may require secondary endovascular or surgical intervention. It may also lead to graft failure (Antonello 2005a). Despite the challenges, endovascular stent grafting is more appealing than surgery because it may carry minimal morbidity and lead to shorter recovery times (Midy 2010). Indeed, now there is an increasing trend towards endovascular treatment for both symptomatic and even asymptomatic PAA (Wrede 2018). Recent studies have suggested that it can offer acceptable patency rates. For example, in a study of 73 patients with PAAs that were managed with endovascular stent grafts the five‐year primary patency rate was 70% and the assisted patency rate was 76%. The five‐year primary patency rate improved to 80% with enhanced technical expertise and the addition of clopidogrel to postoperative patient management (Tielliu 2007). One of the arguments in favour of endovascular first approach is that, the autologous vein conduit is still available for possible future surgical intervention. However, performing a salvage surgical bypass in a patient with failed stent graft can be more challenging, especially if the site of distal anastomosis has been used for landing the distal end of the stent graft. This review brings together trial evidence to evaluate the advantages and disadvantages of endovascular stent grafts compared to conventional open surgical repair of PAA. This will help the clinicians to decide on the optimum treatment strategy for PAA.
Objectives
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.
Methods
Criteria for considering studies for this review
Types of studies
We included randomised controlled trials (RCTs).
Types of participants
We included participants undergoing unilateral or bilateral prophylactic repair for asymptomatic PAA.
Types of interventions
We included RCTs comparing endovascular stent grafting versus conventional open surgical repair of asymptomatic PAA.
Types of outcome measures
Primary outcomes
Primary patency rate at one and four years. According to the Trans‐Atlantic Inter‐Society Consensus (TASC) document, primary patency indicates uninterrupted patency following initial graft deployment (Dormandy 2000).
Assisted primary patency rate at one and four years. This conveys the cases in which a revision or a revascularisation method is applied to prevent impending occlusion or progression of stenosis (Dormandy 2000).
Secondary outcomes
Length of hospital stay.
Operating time or time taken for the procedure to be completed.
Limb salvage.
Wound complications (bleeding, haematoma, seroma and infection).
Search methods for identification of studies
Electronic searches
The Cochrane Vascular Information Specialist conducted systematic searches of the following databases for randomised controlled trials and controlled clinical trials without language, publication year or publication status restrictions:
the Cochrane Vascular Specialised Register via the Cochrane Register of Studies (CRS‐Web searched on 29 January 2019);
the Cochrane Central Register of Controlled Trials (CENTRAL) Cochrane Register of Studies Online (CRSO 2018, issue 12);
MEDLINE (Ovid MEDLINE® Epub Ahead of Print, In‐Process & Other Non‐Indexed Citations, Ovid MEDLINE® Daily and Ovid MEDLINE®) (searched from 1 January 2017 to 29 January 2019);
Embase Ovid (searched from 1 January 2017 to 29 January 2019);
CINAHL Ebsco (searched from 1 January 2017 to 29 January 2019):
AMED Ovid (searched from 1 January 2017 to 29 January 2019).
The Information Specialist modelled search strategies for other databases on the search strategy designed for CENTRAL. Where appropriate, they were combined with adaptations of the highly sensitive search strategy designed by the Cochrane Collaboration for identifying randomised controlled trials and controlled clinical trials (as described in the Cochrane Handbook for Systematic Reviews of Interventions Chapter 6, Lefebvre 2011). Search strategies for major databases are provided in Appendix 1.
The Information Specialist searched the following trials registries on 29 January 2019:
the World Health Organization International Clinical Trials Registry Platform (who.int/trialsearch);
ClinicalTrials.gov (clinicaltrials.gov).
Searching other resources
We checked the reference lists of relevant articles for any additional possible studies.
Data collection and analysis
Selection of studies
Two review authors (DJ and YG) independently assessed the titles and abstracts of reports identified by the search and obtained the full texts for those which met the criteria listed in Criteria for considering studies for this review. Two authors (DJ and CM) independently assessed these reports for inclusion. Any disagreements were resolved by discussion or arbitration by the third author (BG).
Data extraction and management
The review authors (DJ and CM) extracted data independently using proformas designed by Cochrane Vascular. Discrepancies were settled by discussion with the senior author (BG). If required, authors of individual studies were contacted to obtain more information such as missing data.
Assessment of risk of bias in included studies
We used Cochrane's 'Risk of bias' tool for assessing bias (Higgins 2011), independently by two authors (DJ and YG). Discrepancies between the authors' assessments were resolved through discussion with the third author (BG). The results of the assessment of bias of each study were presented in a 'Risk of bias' table and 'Risk of bias' graph (Higgins 2011).
Measures of treatment effect
We used Review Manager 2014 to perform statistical analysis according to Cochrane Vascular's statistical guidelines for review authors. We analysed the time‐to‐event data for the primary outcomes (primary and assisted patency rates of the graft) as dichotomous data because the status of all participants in a study are likely to be known at a fixed time point. Hence, the patency rates were expressed as risk ratios (RR) with 95% confidence intervals (CI).
The secondary outcomes were measured as follows:
The length of hospital stay and the time taken for the procedure to be completed: the methods for measures of continuous outcomes were employed and the difference in the mean number of days spent in the hospital and the mean time taken for the procedure to be completed were measured amongst the two groups of participants. The published report of the included RCT provided the range but did not include the standard deviation (SD) as the measure of variance. An approximate SD was derived from the formula SD = range/4 (Taylor 2014).
Wound complications and limb salvage: we treated the presence or absence of wound complications and limb salvage as dichotomous data, and expressed the outcomes as RRs.
Unit of analysis issues
The unit of analysis in this review is the PAA rather than the participant. Therefore, if a participant had bilateral popliteal artery aneurysms and both aneurysms were randomised and operated on independently of each other then they were counted as two events rather than one. We ensured that the studies followed a simple parallel group design for clinical trials, that is the number of observations in the final analysis matched the number of units that were randomised. We planned to make appropriate corrections if this was not the case. However, it was not necessary on this occasion.
Dealing with missing data
There were no missing data reported in the included study. If there are any missing data in the studies included in the future, we will ignore data 'missing at random' and analyse only the available data as the missing data are unlikely to make any significant change in the outcome. For the data that are deemed to be 'not missing at random' we will contact the original investigators. If no clear answer is available, we will allocate replacement values equal to the mean of the available values. We will perform a sensitivity analysis to assess how sensitive the results are to the reasonable changes in the assumptions that were made. The potential impact will be addressed in the Discussion section.
Assessment of heterogeneity
We did not perform tests for heterogeneity as only one trial was included. If sufficient trials are available for analysis in future updates, we will assess the degree of heterogeneity amongst the trials by using the I2 statistic according to the formula I2 = 100% × (Q ‐ degrees of freedom)/Q, where Q is the Chi2 statistic (Higgins 2011). If significant heterogeneity is present, we will calculate a summary statistic for each outcome using a random‐effects model.
Assessment of reporting biases
As there was only one study available, the publication bias was not assessed.
Data synthesis
Where possible, we will perform a fixed‐effect model meta‐analysis if sufficient trials become available in the future. This is based on the assumption that each study will estimate the primary and assisted patency rates of the grafts as primary endpoints. We will use the standard error of the summary (pooled) intervention effect to obtain the following:
the confidence interval (CI), which will estimate the accuracy (or ambiguity) of the summary estimate;
the P value, which will reveal the strength of the evidence against the null hypothesis of no significant difference between endovascular repair and conventional open repair of asymptomatic PAA.
Subgroup analysis and investigation of heterogeneity
We did not perform subgroup analysis as there was only one trial included in this review. In future, if there is an adequate number of trials to merit subgroup analysis, we may consider some groups of participants separately. For example, subgroups can be created if one trial uses a different kind of stent graft to the others. Due to the limited range of commercially‐available stent grafts, however, it seems unlikely that an additional subgroup will be required.
Sensitivity analysis
We did not perform sensitivity analysis as there was only one trial included. If significant heterogeneity is present in future updates, we will perform sensitivity analyses by repeating the analysis after omitting the trials which have low scores on individual quality items.
Summary of findings and assessment of the certainty of the evidence
We presented the main findings of this review in a 'Summary of findings' table (see Table 1). We created a table for the comparison of endovascular treatment versus surgical treatment using GRADEpro GDT 2015, and we included the outcomes primary patency at four years, assisted primary patency at four years, length of hospital stay and operating time. We assessed the certainty of the body of evidence using the specific evidence grading system developed by the GRADE working group (GRADE Working Group 2004). We made judgements on the certainty of the evidence transparent by using footnotes in the 'Summary of findings' table.
Results
Description of studies
See: Characteristics of included studies; Characteristics of excluded studies
Results of the search
See: Figure 1
1.
Study flow diagram.
Included studies
No new studies were identified for this 2019 update. The only included study (Antonello 2005), is described below in the table Characteristics of included studies.
Excluded studies
One previous ongoing study has now been excluded as it has been terminated due to unsuccessful trial accrual (NCT01817660).
Risk of bias in included studies
The only included study was a randomised, controlled single‐centre trial. An in‐depth description of the methods is provided in the original article (Antonello 2005). The relevant regulatory bodies of the institution approved and monitored the study. The details of the risk of bias assessment are described in Figure 2.
2.
Risk of bias summary: review authors' judgements about each risk of bias item for each included study.
Allocation
The randomisation was performed by using sealed opaque envelopes containing the allocation to group A or group B. The envelopes, put into a container in blocks of 10 (five group A, five group B) were extracted by the study controller a day before the operation. If a participant did not wish to be included in the study, he or she was excluded from the trial (low risk of bias).
Blinding
There was no blinding of the trial participants or personnel as it would have been impractical to do so (unclear risk of bias). The trial outcome is unlikely to have been affected by this. The follow‐up of the graft or the stent graft was performed independently and in an objective fashion: a stenosis of greater then 50% was considered an indication for re‐intervention to prevent an occlusion (low risk of bias).
Incomplete outcome data
None of the trial participants were lost to follow‐up. However, any wound complications including infection, haematoma and seroma were not documented (unclear risk of bias).
Selective reporting
The initial trial protocol was not available, hence it was not possible to comment if there were any outcomes that were not reported in the completed trial (unclear risk of bias).
Other potential sources of bias
The main limitation of the trial was that it included a lower number of participants than it initially calculated in order to achieve a statistically significant difference at one‐year follow‐up and the study was therefore underpowered. However, PAA is a relatively uncommon condition and it was not possible to enrol a large number of participants from the same centre (unclear risk of bias).
Effects of interventions
See: Table 1
Primary patency rates at one and four years
The effects of the intervention have been derived from a single RCT with 15 PAA randomised to each group (30 total). The initial trial period took place over five years (Antonello 2005); hence the mean follow‐up period was 45.9 months (range 12 to 65 months) for the endovascular group and 46.1 months (range 12 to 72 months) for the surgical group. In the endovascular group, two stents occluded: one in the early post‐operative period and the other one in the late post‐operative period. The cause of the blockages was attributed to more than 20% oversizing of the stent with respect to the popliteal artery (some oversizing of the stent graft is essential to obtain a snug fit). The early post‐operative blockage was treated by an endovascular approach while the late blockage required a surgical bypass. In the surgical group, there were two late occlusions of the bypass grafts that were detected on the surveillance ultrasound scan, performed at 24 months and 48 months. The participants only had intermittent claudication hence no treatment was initiated. The one‐year primary patency rate of the endovascular treatment versus surgical treatment was 93.3% versus 100%; RR 0.94, 95% CI 0.78 to 1.12; P = 0.47; moderate‐certainty evidence; Analysis 1.1), the four‐year primary patency rates of both the endovascular and the surgical groups were similar: two occlusions each in the 15 PAAs treated (86.6%; RR 1.00, 95% CI 0.76 to 1.32; P = 1.00; moderate‐certainty evidence; Analysis 1.2).
1.1. Analysis.
Comparison 1 Endovascular versus open surgical repair of asymptomatic popliteal artery aneurysm, Outcome 1 Primary patency rate at 1 year.
1.2. Analysis.
Comparison 1 Endovascular versus open surgical repair of asymptomatic popliteal artery aneurysm, Outcome 2 Primary patency rate at 4 years.
Some of the participants in the initial RCT were not followed up for four years. These additional data were obtained from a subsequent publication by the same authors (Antonello 2007), which meant that all participants in the initial group had at least a four‐year follow‐up. In the later trial period all participants from the initial trial were followed up for three more years (Antonello 2007). An additional 12 cases were included in the surgical group and six cases were included in the endovascular group. These additional cases were not randomised hence we have not included them in this review. In this new group of participants there were only two complications, both of which took place within two months of the index procedure. The remaining complications listed in the later study were identical to the complications in the report on the initial RCT (Antonello 2005), hence it can be assumed that there were no further complications in the randomised participants in the completed four‐year follow‐up period.
Assisted patency rate at one and four years
One endovascular stent graft was occluded in the early post‐operative period. It was made patent by performing another endovascular procedure. Two more stent grafts were found to have more than 60% stenosis (but not occlusion) in the late post‐operative period. One of these cases was successfully treated by an endovascular approach, while the other required surgery as described in the previous paragraph. The surgical group had two occlusions in the late post‐operative period; however assisted patency was not attempted in these cases due to minimal symptoms. Hence, no differences were detected in the assisted patency rate at one year or four years in the endovascular versus the surgical group respectively ((RR 1.00, 95% CI 0.88 to 1.13; P = 1; moderate‐certainty evidence; Analysis 1.3) and (RR 1.00, 95% CI 0.76 to 1.32; P = 1; moderate‐certainty evidence; Analysis 1.4)).
1.3. Analysis.
Comparison 1 Endovascular versus open surgical repair of asymptomatic popliteal artery aneurysm, Outcome 3 Assisted patency rate at 1 year.
1.4. Analysis.
Comparison 1 Endovascular versus open surgical repair of asymptomatic popliteal artery aneurysm, Outcome 4 Assisted patency rate at 4 years.
Length of hospital stay
The length of hospital stay was reduced in the endovascular group as compared to the surgical group (mean 4.3 days versus 7.7 days; mean difference (MD) ‐3.40 days, 95% CI ‐4.42 to ‐2.38; P < 0.001; moderate‐certainty evidence; Analysis 1.5).
1.5. Analysis.
Comparison 1 Endovascular versus open surgical repair of asymptomatic popliteal artery aneurysm, Outcome 5 Length of hospital stay.
Operating time
The operating time was reduced in the endovascular group compared to the surgical 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; Analysis 1.6).
1.6. Analysis.
Comparison 1 Endovascular versus open surgical repair of asymptomatic popliteal artery aneurysm, Outcome 6 Operating time.
Limb salvage
None of the participants in the study underwent an amputation. Hence, there was no difference in the limb salvage rate between the endovascular and the surgical groups (RR 1.00, 95% CI 0.88 to 1.13; P = 1; moderate‐certainty evidence; Analysis 1.7).
1.7. Analysis.
Comparison 1 Endovascular versus open surgical repair of asymptomatic popliteal artery aneurysm, Outcome 7 Limb salvage at 4 years.
Wound complications
Wound complications including bleeding, haematoma, infection and seroma were not published in the report of the included RCT.
Discussion
Summary of main results
An untreated PAA can cause severe morbidity. The treatment may be either endovascular or surgical. There is currently no clear evidence to suggest better outcomes with one treatment over the other in a non‐emergency setting. Conventional surgical repair is still considered by some as the gold standard. On the other hand, several large retrospective case series have established the safety of the endovascular approach. However, there is little level‐1 evidence comparing the two techniques. We found only one RCT that was published in 2005 (Antonello 2005). Unlike abdominal aortic aneurysm (AAA), PAAs are relatively uncommon and the included RCT was conducted in a single centre, which resulted in an underpowered study. See Table 1. Most cases achieved a four‐year follow‐up during the trial, however the data for the completed four‐year follow‐up of the remaining participants were obtained from the authors' subsequent publication (Antonello 2007). Antiplatelet therapy in the form of aspirin was used indefinitely in both groups. Two cases required embolisation of the collateral vessels prior to the endovascular treatment to prevent type‐2 endoleak. There is moderate‐certainty evidence that one‐year primary patency rate was higher in the surgical group, however the four‐year primary patency rates of both the endovascular and the surgical groups were similar (two occlusions each, moderate‐certainty evidence). There was no difference in the assisted patency rate and limb salvage at four years in the endovascular versus the surgical group (moderate certainty evidence). Both occlusions in the surgical bypass group were present in the prosthetic graft category. There were no occlusions in the autologous vein category. The stent graft occlusions were attributed to adverse anatomy and oversizing of the stent graft (> 20%). The operating time and the length of hospital stay were reduced in the endovascular group (moderate‐certainty evidence). The study did not report on wound complications.
Overall completeness and applicability of evidence
Only one small underpowered study was identified for inclusion in the review. Wound complications were not reported by the trialists. The study does, however, demonstrate the safety of endovascular non‐emergency treatment of PAA compared with conventional open repair. Indeed, with adequate surveillance for evolving stenotic lesions the long‐term assisted patency approaches that of conventional open repair.
Quality of the evidence
A single study has been included in this review, which provided moderate‐certainty evidence based on the GRADE system for evaluating the certainty of the evidence. While the study had a robust design and consistent results, there are concerns with regards to the precision of the results. As shown in the Table 1 there were a limited number of participants included in the study, which led to wide confidence intervals for the primary and secondary outcomes of the trial. We downgraded each outcome from high to moderate‐certainty evidence due to imprecision.
Potential biases in the review process
The search for suitable studies was conducted independently by the Cochrane Vascular Information Specialist. The selection of suitable studies was performed independently by two review authors (DJ and RJ). No discrepancies arose in the selection process. The unit of analysis for this review is the PAA instead of the individual. This is a potential selection bias, however we believe that the outcome of treatment of PAA on one side is unlikely to affect the outcome of treatment on the other side. According to the study four individuals had bilateral PAAs, which were randomised independently of each other and received treatment on different occasions. Two participants received endovascular treatment for both PAAs, while the other two participants underwent surgical repair on one side and endovascular repair on the other side. The included study reported number of occlusions and percentage patency rate. We deemed occlusion an inverse event with respect to the primary outcome of patency, i.e. the occluded grafts are equal to the total procedures minus the number of patent grafts/stent grafts.
Agreements and disagreements with other studies or reviews
Our results are consistent with a recent meta‐analysis of 14 studies that included 4880 popliteal artery aneurysm repairs (3915 open surgery and 1210 endovascular) (Leake 2017). The meta‐analysis included randomised as well as non‐randomised studies. It concluded that the open surgery patients were younger and more likely to have worse tibial runoff than endovascular patients. As expected, open surgery patients had increased incidence of wound complications and longer hospital stay, however, fewer re‐interventions and lower thrombotic complications. The primary patency was better for open surgery at one year and three years, however, there was no difference between the groups in assisted primary patency at one year and three years.
Authors' conclusions
Implications for practice.
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.
Implications for research.
There is a need for further randomised trials with adequate sample sizes to confidently ascertain any advantage of endovascular repair over surgical repair of asymptomatic PAA. This will only be possible with a multicentre trial as it is not possible to recruit a large number of patients from a single centre. One multicentre RCT (NCT01817660), was terminated prematurely as it was unable to recruit enough patients. A larger multicentre 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.
What's new
| Date | Event | Description |
|---|---|---|
| 4 September 2019 | New search has been performed | New search run. No new studies identified. |
| 4 September 2019 | New citation required but conclusions have not changed | New search run. No new studies identified. New authors joined team. Text updated to reflect current Cochrane standards. No change to conclusions. |
Acknowledgements
The authors thank Professor Jonathan Sterne, Head of HSR Division and Professor of Medical Statistics and Epidemiology, University of Bristol, UK for advice on the statistics for the proposed meta‐analysis. The authors also acknowledge the co‐authors of the previous version of the review, Dr Lyn Jones, Consultant Radiologist, Sothmead Hospital, Bristol, UK and Dr Richard James, Consultant Radiologist, Royal United Hospitals Bath NHS Trust, Bath, UK.
Appendices
Appendix 1. Database search strategies
| Source | Search strategy | Hits retrieved |
| CENTRAL via CRSO | #1 MESH DESCRIPTOR Aneurysm EXPLODE ALL TREES 1287 #2 MESH DESCRIPTOR Popliteal Artery EXPLODE ALL TREES 309 #3 PAA :TI,AB,KY 69 #4 EVPAR :TI,AB,KY 0 #5 (popliteal ADJ5 aneurysm* ):TI,AB,KY 10 #6 (peripheral ADJ5 aneurysm* ):TI,AB,KY 11 #7 #1 OR #2 OR #3 OR #4 OR #5 OR #6 1670 #8 MESH DESCRIPTOR Endovascular Procedures EXPLODE ALL TREES 7611 #9 MESH DESCRIPTOR Blood Vessel Prosthesis EXPLODE ALL TREES 433 #10 MESH DESCRIPTOR Blood Vessel Prosthesis Implantation EXPLODE ALL TREES 435 #11 MESH DESCRIPTOR Stents EXPLODE ALL TREES 3810 #12 *stent* :TI,AB,KY 53944 #13 *graft* :TI,AB,KY 25749 #14 (endovasc* or EVAR or percutan* or endolumin* ):TI,AB,KY 16306 #15 (haemobahn or hemobahn ):TI,AB,KY 3 #16 viabahn :TI,AB,KY 26 #17 wallgraft :TI,AB,KY 2 #18 nitinol :TI,AB,KY 264 #19 palmaz :TI,AB,KY 94 #20 lifestent :TI,AB,KY 5 #21 MESH DESCRIPTOR Vascular Surgical Procedures 604 #22 MESH DESCRIPTOR Ligation EXPLODE ALL TREES 581 #23 ligat* :TI,AB,KY 2392 #24 #8 OR #9 OR #10 OR #11 OR #12 OR #13 OR #14 OR #15 OR #16 OR #17 OR #18 OR #19 OR #20 OR #21 OR #22 OR #23 93060 #25 #7 AND #24 844 #26 01/01/2014 TO 29/01/2019:CD 579835 #27 #25 AND #26 290 |
290 |
| Clinicaltrials.gov | Aneurysm OR Popliteal Artery OR PAA OR EVPAR | stent OR stents OR graft OR Blood Vessel Prosthesis OR surgical procedure OR ligation | Start date on or after 01/01/2014 | Last update posted on or before 01/29/2019 | 209 |
| ICTRP Search Portal | Aneurysm OR Popliteal Artery OR PAA OR EVPAR | stent OR stents OR graft OR Blood Vessel Prosthesis OR surgical procedure OR ligation | Start date on or after 01/01/2014 | 106 |
| Medline (Ovid MEDLINE® Epub Ahead of Print, In‐Process & Other Non‐Indexed Citations, Ovid MEDLINE® Daily and Ovid MEDLINE®) 1946 to present 2017, 2018 and 2019 only |
1 exp Aneurysm/ 2 exp Popliteal Artery/ 3 (popliteal adj5 aneurysm*).ti,ab. 4 (peripheral adj5 aneurysm*).ti,ab. 5 PAA.ti,ab. 6 EVPAR.ti,ab. 7 or/1‐6 8 exp Endovascular Procedures/ 9 exp Blood Vessel Prosthesis/ 10 exp Blood Vessel Prosthesis Implantation/ 11 exp Stents/ 12 Vascular Surgical Procedures/ 13 exp Ligation/ 14 stent*.ti,ab. 15 graft*.ti,ab. 16 (endovasc* or EVAR or percutan* or endolumin*).ti,ab. 17 (haemobahn or hemobahn).ti,ab. 18 viabahn.ti,ab. 19 wallgraft.ti,ab. 20 nitinol.ti,ab. 21 palmaz.ti,ab. 22 lifestent.ti,ab. 23 ligat*.ti,ab. 24 or/8‐23 25 7 and 24 26 randomized controlled trial.pt. 27 controlled clinical trial.pt. 28 randomized.ab. 29 placebo.ab. 30 drug therapy.fs. 31 randomly.ab. 32 trial.ab. 33 groups.ab. 34 or/26‐33 35 exp animals/ not humans.sh. 36 34 not 35 37 25 and 36 38 (2017* or 2018* or 2019*).ed. 39 37 and 38 40 from 39 keep 1‐856 |
856 |
| EMBASE 2017, 2018 and 2019 only | 1 exp aneurysm/ 2 exp popliteal artery/ 3 (popliteal adj5 aneurysm*).ti,ab. 4 (peripheral adj5 aneurysm*).ti,ab. 5 PAA.ti,ab. 6 EVPAR.ti,ab. 7 or/1‐6 8 exp endovascular surgery/ 9 exp blood vessel prosthesis/ 10 exp Blood Vessel Prosthesis Implantation/ 11 exp stent/ 12 vascular surgery/ 13 exp ligation/ 14 stent*.ti,ab. 15 graft*.ti,ab. 16 (endovasc* or EVAR or percutan* or endolumin*).ti,ab. 17 (haemobahn or hemobahn).ti,ab. 18 viabahn.ti,ab. 19 wallgraft.ti,ab. 20 nitinol.ti,ab. 21 palmaz.ti,ab. 22 lifestent.ti,ab. 23 ligat*.ti,ab. 24 or/8‐23 25 7 and 24 26 randomized controlled trial/ 27 controlled clinical trial/ 28 random$.ti,ab. 29 randomization/ 30 intermethod comparison/ 31 placebo.ti,ab. 32 (compare or compared or comparison).ti. 33 ((evaluated or evaluate or evaluating or assessed or assess) and (compare or compared or comparing or comparison)).ab. 34 (open adj label).ti,ab. 35 ((double or single or doubly or singly) adj (blind or blinded or blindly)).ti,ab. 36 double blind procedure/ 37 parallel group$1.ti,ab. 38 (crossover or cross over).ti,ab. 39 ((assign$ or match or matched or allocation) adj5 (alternate or group$1 or intervention$1 or patient$1 or subject$1 or participant$1)).ti,ab. 40 (assigned or allocated).ti,ab. 41 (controlled adj7 (study or design or trial)).ti,ab. 42 (volunteer or volunteers).ti,ab. 43 trial.ti. 44 or/26‐43 45 25 and 44 46 (2017* or 2018* or 2019*).em. 47 45 and 46 48 from 47 keep 1001‐1648 |
1648 |
| CINAHL 2017, 2018 and 2019 only | S39 S37 AND S38 S38 EM 2017 OR EM 2018 OR 2019 EM S37 S23 AND S36 S36 S24 OR S25 OR S26 OR S27 OR S28 OR S29 OR S30 OR S31 OR S32 OR S33 OR S34 OR S35 S35 MH "Random Assignment" S34 MH "Single‐Blind Studies" or MH "Double‐Blind Studies" or MH "Triple‐Blind Studies" S33 MH "Crossover Design" S32 MH "Factorial Design" S31 MH "Placebos" S30 MH "Clinical Trials" S29 TX "multi‐centre study" OR "multi‐center study" OR "multicentre study" OR "multicenter study" OR "multi‐site study" S28 TX crossover OR "cross‐over" S27 AB placebo* S26 TX random* S25 TX trial* S24 TX "latin square" S23 S7 AND S22 S22 S8 OR S9 OR S10 OR S11 OR S12 OR S13 OR S14 OR S15 OR S16 OR S17 OR S18 OR S19 OR S20 OR S21 S21 TX ligat* S20 TX lifestent S19 TX palmaz S18 TX nitinol S17 TX wallgraft S16 TX viabahn S15 TX haemobahn or hemobahn S14 TX endovasc* or EVAR or percutan* or endolumin* S13 TX graft* S12 TX stent* S11 (MH "Ligation") S10 (MH "Stents+") S9 (MH "Blood Vessel Prosthesis") S8 (MH "Endovascular Procedures+") S7 S1 OR S2 OR S3 OR S4 OR S5 OR S6 S6 TX EVPAR S5 TX PAA S4 TX peripheral N5 aneurysm* S3 TX popliteal N5 aneurysm* S2 (MH "Popliteal Artery") S1 (MH "Aneurysm+") |
123 |
| AMED 2017, 2018 and 2019 only | 1 exp aneurysm/ 2 (peripheral adj5 aneurysm*).ti,ab. 3 PAA.ti,ab. 4 EVPAR.ti,ab. 5 popliteal.ti,ab. 6 or/1‐5 7 exp Stents/ 8 stent*.ti,ab. 9 graft*.ti,ab. 10 (endovasc* or EVAR or percutan* or endolumin*).ti,ab. 11 (haemobahn or hemobahn).ti,ab. 12 viabahn.ti,ab. 13 wallgraft.ti,ab. 14 nitinol.ti,ab. 15 palmaz.ti,ab. 16 lifestent.ti,ab. 17 ligat*.ti,ab. 18 or/7‐17 19 6 and 18 20 exp CLINICAL TRIALS/ 21 RANDOM ALLOCATION/ 22 DOUBLE BLIND METHOD/ 23 Clinical trial.pt. 24 (clinic* adj trial*).tw. 25 ((singl* or doubl* or trebl* or tripl*) adj (blind* or mask*)).tw. 26 PLACEBOS/ 27 placebo*.tw. 28 random*.tw. 29 PROSPECTIVE STUDIES/ 30 or/20‐29 31 19 and 30 |
0 |
Data and analyses
Comparison 1. Endovascular versus open surgical repair of asymptomatic popliteal artery aneurysm.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 Primary patency rate at 1 year | 1 | 30 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.94 [0.78, 1.12] |
| 2 Primary patency rate at 4 years | 1 | 30 | Risk Ratio (M‐H, Fixed, 95% CI) | 1.0 [0.76, 1.32] |
| 3 Assisted patency rate at 1 year | 1 | 30 | Risk Ratio (M‐H, Fixed, 95% CI) | 1.0 [0.88, 1.13] |
| 4 Assisted patency rate at 4 years | 1 | 30 | Risk Ratio (M‐H, Fixed, 95% CI) | 1.0 [0.76, 1.32] |
| 5 Length of hospital stay | 1 | 30 | Mean Difference (IV, Fixed, 95% CI) | ‐3.40 [‐4.42, ‐2.38] |
| 6 Operating time | 1 | 30 | Mean Difference (IV, Fixed, 95% CI) | ‐119.90 [‐137.71, ‐102.09] |
| 7 Limb salvage at 4 years | 1 | 30 | Risk Ratio (M‐H, Fixed, 95% CI) | 1.0 [0.88, 1.13] |
Characteristics of studies
Characteristics of included studies [ordered by study ID]
Antonello 2005.
| Methods | Prospective single‐centre randomised clinical trial conducted over a period of 5 years (January 1999 to December 2003) | |
| Participants | A total of 30 PAA were randomly treated in 26 patients (four with bilateral PAA) Inclusion criteria: All patients 50 years or older with asymptomatic PAA measuring more than 2 cm in the short axis and proximal and distal necks measuring more than 1 cm in long axis Exclusion criteria: Poor distal run‐off (blockage of more than 1 of 3 leg arteries); contraindication to anticoagulation or antiplatelet therapy and pressure symptoms causing nerve or vein compression |
|
| Interventions |
Group A (endovascular group): endovascular exclusion of the PAA using a covered, self expanding stent graft made up of nitinol scaffolding lined by PTFE (Hemobahn, W.L. Gore & Assoc, Flagstaff, Ariz) Group B (surgical group): open surgical exclusion and bypass of the PAA using an autologous vein or a PTFE graft via lateral approach |
|
| Outcomes | Primary endpoints:
Secondary endpoints:
|
|
| Notes |
|
|
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | The randomisation was performed by using sealed opaque envelopes containing the allocation to the group A or group B. The envelopes, put into a container in blocks of 10 (five group A, five group B) were extracted by the study controller a day before the operation |
| Allocation concealment (selection bias) | Low risk | The randomisation was performed by using sealed opaque envelopes containing the allocation to the group A or group B. The envelopes, put into a container in blocks of 10 (five group A, five group B) were extracted by the study controller a day before the operation |
| Blinding of participants and personnel (performance bias) All outcomes | Unclear risk | The blinding has not been described in the publication; however it may not have been practical in this case |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | The outcome of the graft patency would be by means of an ultrasound or a cross‐sectional imaging technique. This would usually result in an objective assessment of the patency of the graft or stent. Underestimation of the stenosis would have led to graft or stent occlusion. Hence, we believe that there is a low risk of bias |
| Incomplete outcome data (attrition bias) All outcomes | Unclear risk | None of the participants were lost to follow‐up. However, the authors have not published the wound complications and the operative risk of the enrolled participants |
| Selective reporting (reporting bias) | Unclear risk | The initial trial protocol is not available |
| Other bias | Unclear risk | The study is underpowered. However, it would not have been possible to recruit many participants from a single centre for a relatively uncommon condition |
cm: centimetre PAA: popliteal artery aneurysm PTFE: polytetrafluoroethylene
Characteristics of excluded studies [ordered by study ID]
| Study | Reason for exclusion |
|---|---|
| NCT01817660 | This study met the inclusion criteria but was terminated due to unsuccessful trial accrual |
Differences between protocol and review
For the previous version of the review (Joshi 2014), we included the primary and assisted patency rates at one‐year and four‐years as opposed to four‐years only. This was done to provide an overview of the short‐term as well as the long‐term patency of the grafts. We clarified that the unit of analysis for the review is the randomised PAA and not the participant in the unit of analysis section. In order to adhere to the reporting standards of Cochrane reviews we included GRADE (GRADE Working Group 2004) as a method for assessing the quality of the evidence and included a 'Summary of findings' table.
Contributions of authors
DJ: acquisition of trial reports, trial selection, data extraction, data entry into RevMan, data analysis, data interpretation, clinical input, review drafting, future review updating, guarantor of the review YG: trial selection, data analysis, clinical input, review drafting BG: trial selection, data analysis, clinical input, review drafting CM: trial selection, data analysis, clinical input, review drafting
Sources of support
Internal sources
No sources of support supplied
External sources
-
Chief Scientist Office, Scottish Government Health Directorates, The Scottish Government, UK.
The Cochrane Vascular editorial base is supported by the Chief Scientist Office
Declarations of interest
DJ: none known YG: none known BG: none known CM: none known
New search for studies and content updated (no change to conclusions)
References
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