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The aim of this study was to evaluate long-term outcomes following surgery for popliteal artery entrapment syndrome.
Methods
A retrospective study of all patients that underwent surgery for popliteal artery entrapment syndrome between January 2003 and December 2009 was performed. Patient demographic data, clinical features, imaging modalities, and surgical management were recorded. The primary outcome was 5 year patency.
Results
Eighteen patients (25 limbs) underwent surgery. The mean age at the time of surgical procedure was 35 (median 35 years; range 15–49). Presentation was bilateral in seven patients (39%). Diagnosis was made using various imaging modalities, including position stress test, Duplex ultrasonography, computed tomography angiography, magnetic resonance imaging and conventional angiography. In four limbs the popliteal artery was compressed and undamaged (16%), and treatment consisted of musculo-tendinous division alone. In 16 limbs the popliteal artery was damaged with lesions limited to the popliteal artery (64%) where treatment consisted of venous interposition. In five limbs lesions extended beyond the popliteal artery (20%) and procedures included one below knee femoro-popliteal bypass, three femoro-posterior tibial bypasses, and one popliteo-posterior tibial bypass. Musculo-tendinous division was associated with vascular reconstruction in 19 limbs (90%). Mean follow up was 82 months (median 81 months, range 60–120). Five year patency was 84%.
Conclusion
Long-term outcomes of surgical procedures performed for popliteal artery entrapment syndrome can be considered satisfactory.
The long-term follow up data of patients who were treated by surgical revascularization for popliteal artery entrapment syndrome were retrospectively reviewed. It was shown that surgical reconstruction provides good long-term graft patency when lesions are limited to the popliteal artery. In the case of extensive lesions upstream or downstream from the popliteal artery, outcomes are significantly worse. This highlights the need for early detection and treatment.
Introduction
Popliteal artery entrapment syndrome (PAES) results from an abnormal anatomical relationship between the popliteal artery and the surrounding musculo-tendinous structures. It was first described by Stuart in 1879, with the first operative treatment reported 80 years later.
It is thus believed to be responsible for a significant proportion of vascular symptoms, mostly intermittent claudication in young patients without atherosclerotic risk factors.
It can be a source of significant disability and impairment, and can lead to progressive injury to the popliteal artery with the risk of subsequent limb loss.
The surgical strategy for PAES depends on the clinical presentation, the extent of the arterial injury (arterial lesions can be limited to the popliteal artery or sometimes extend to distal run off), and the underlying anatomic abnormalities.
Surgical release of the entrapping mechanism is the treatment of choice when the popliteal artery remains intact. In case of a damaged or occluded popliteal artery, vascular reconstruction is generally needed.
However, the diagnosis is often made at an advanced stage of disease because of late presentation or misdiagnosis, with either patients or primary medical referrals neglecting or minimizing the significance of limb pain, and frequently allocating the symptoms to muscular or joint damage. Surgical reconstruction is normally mandatory in these cases and long-term patency should be guaranteed in these young patients if possible.
The aim of this study was to evaluate the 5 year outcomes of surgical management for PAES and to investigate whether patency is affected by the initial extent of the arterial lesion.
Materials and Methods
The institutional review board approved this retrospective study and waived the requirement for informed consent.
Design of the study
All patients with PAES who underwent surgery in the Department of Vascular Surgery, University Hospital of Strasbourg between January 2003 and December 2009 were included retrospectively.
Pre-operative parameters
The following pre-operative parameters were recorded: demographic data (age, sex), cardiovascular risk factors (hypertension, diabetes mellitus, dyslipidemia, active smoking, obesity), participation in sport, length of evolution, and clinical presentation (claudication, rest pain, tissue lesion). Data concerning these parameters were prospectively collected from a dedicated institutional database, and analyzed retrospectively.
The pre-operative diagnosis of PAES was made using various modalities. Ankle brachial pressure index (ABI) was calculated at rest, and a positional stress test (PST) was performed in all patients. PST was considered positive when pedal pulses could be palpated in normal leg position but disappeared during dorsiflexion against resistance. Duplex ultrasonography and computed tomography angiography (CTA) with dynamic testing were also performed in all patients. Conventional angiography, and/or magnetic resonance imaging (MRI) were performed, if necessary, to confirm the diagnosis when CTA was not adequate or to study the outflow vessels, depending on the surgical strategy.
Pre- and post-operative parameters
Revascularization procedures were recorded. The choice of surgical strategy depended on the anatomy of the popliteal fossa and the features of the popliteal artery. Musculo-tendinous division alone was performed for a compressed and undamaged popliteal artery. For a damaged popliteal artery with lesions strictly limited to it, a venous interposition bypass using reversed great saphenous vein with end to end anastomoses was performed. When the lesion extended up beyond the adductor canal or down to the popliteal trifurcation, a venous bypass using reversed great saphenous vein with end to side anastomosis was performed. Musculo-tendinous division was associated with vein interposition or bypass as determined by radiological and pre-operative findings. The quality of the vein used for the vascular reconstruction was assessed by pre-operative duplex ultrasonography.
The post-operative 30 day mortality and 30 day morbidity were recorded. Morbidity was defined as surgery related morbidity (thrombosis, nerve palsy, hemorrhagic complication, operative site infection) or systemic morbidity (renal, pulmonary, cardiac, or neurologic failures).
Long-term follow up consisted of clinical examination and duplex ultrasonography 1 month after the surgery, and every 6 months thereafter.
Classification
Based on radiological and operative findings, PAES was classified according to the classification of Insua et al.
In type I PAES the medial head of the gastrocnemius muscle arises normally from the upper posterior medial condyle of the femur, and the popliteal artery is displaced in an exaggerated loop passing medially around and beneath the muscle origin. In type II PAES the medial head of the gastrocnemius muscle arises laterally and the artery descends medially and beneath it, but its course is vertical and does not show exaggerated looping. In type III PAES the popliteal artery is compressed by an accessory slip of muscle from the medial head of the gastrocnemius, being entrapped beneath the accessory head. In type IV PAES the popliteal artery is entrapped by the deeper popliteus muscle or by a fibrous band in the same location. Type V PAES is a venous entrapment and type VI is a functional entrapment, without anatomic abnormality (Fig. 1).
Figure 1The popliteal artery is running medial to the medial head of the gastrocnemius muscle, which has a normal insertion. The arterial detour is pronounced (I). The insertion of the medial head of the gastrocnemius muscle is higher and more lateral (II). The path of the popliteal artery is vertical and does not show exaggerated looping. There is an accessory slip of the medial head of the gastrocnemius muscle that inserts into the inter-condylar region, and compresses the popliteal artery when joining the medial head of the gastrocnemius muscle (III). The popliteal artery is compressed when passing under the popliteal muscle or under a fibrous web (IV). The vein accompanies the popliteal artery in its unusual route and is caught by the same muscular or fibrous entrapment (V). Functional entrapment, without anatomic abnormality.
The primary outcome measure was 5 year graft patency (Fig. 2). A subgroup analysis was performed in order to determine whether patency could be affected by the initial extent of the arterial lesion.
Figure 2Twenty-nine year old man (patient 4, group 1) with left intermittent claudication. Computed tomography angiography (CTA) revealed a supra-articular popliteal occlusion (a). Five year CTA after musculo-tendinous division and popliteo-popliteal interposition showing a patent vein graft (b).
Statistical analysis was performed using GraphPad Prism 5 (GraphPad Software, Inc., La Jolla, CA, USA). Asymmetric quantitative variables are presented as median and interquartile range (IQR). Qualitative variables are presented as effectives and percentages. Fisher's exact or, alternatively, the chi-square test, and the Mann–Whitney U test, or, alternatively, the Student t test were used to perform comparisons, depending on distribution assumptions. Kaplan–Meier analysis was performed in order to determine patency rates. A p-value < .05 was considered statistically significant.
Results
Patients
Between January 2003 and December 2009, 18 patients (25 limbs; 17 men [94%] and one woman [6%]) underwent surgery for PAES.
The mean age at the time of the surgical procedure was 35 (median 35 years; range 15–49 years). Presentation was bilateral in seven patients (39%). Risk factors were hypertension (n = 3; 17%), diabetes mellitus (n = 1; 6%), and active smoking (n = 6; 33%). Nine patients (50%) were regularly participating in sporting activities. Mean duration of symptom evolution was 13 months (median 12 months; range 1–48). Clinical presentation was claudication in 20 limbs (80%), rest pain in four limbs (16%), and tissue lesion in one limb (4%) (Table 1).
Table 1Summary of patient characteristics.
Patient
Age (y)
Sex
Risk factors
Sport
Length (mo)
Side
Clinical presentation
1
45
M
HT
Football
1
L
Rest pain
2
19
F
Smoking
Tennis
12
L
Claudication
3
37
M
None
None
18
R
Tissue lesion
2
L
Claudication
4
29
M
HT
Running
20
L
Claudication
5
35
M
None
Running
15
R
Claudication
6
35
M
Smoking
Running
24
L
Claudication
7
32
M
None
Running
18
R
Claudication
8
45
M
Smoking
None
12
L
Claudication
4
R
Claudication
9
32
M
None
None
18
R
Claudication
10
48
M
Diabetes
None
20
R
Claudication
11
39
M
Smoking
None
12
L
Claudication
12
45
M
HT
None
6
L
Claudication
13
35
M
None
Running
6
R
Claudication
3
L
Claudication
14
37
M
Smoking
None
12
R
Rest pain
15
23
M
None
Football
12
R
Claudication
2
L
Claudication
16
15
M
Smoking
None
24
R
Claudication
5
L
Claudication
17
49
M
None
Football
36
L
Rest pain
4
R
Claudication
18
27
M
None
None
48
R
Rest pain
3
L
Claudication
Note. M = male; HT = hypertension; L = left; F = female; R = right.
Mean pre-operative ABI at rest was 0.83 (median 0.9; IQR 0.2). PST was positive in seven of the 25 limbs (28%).
CTA was performed in all patients, demonstrating the site of occlusion and/or anatomical abnormalities in 12 limbs. Conventional arteriography was performed in 10 limbs in eight patients, and was informative in all cases. It showed compression of the popliteal artery with the ankle plantarflexed, or occlusion of the popliteal artery at the time of presentation. It also showed medial displacement of the artery. MRI was performed in 17 limbs in 11 patients, and demonstrated the underlying abnormalities in 14 limbs by showing the abnormal anatomic relationship between the popliteal artery and the medial head of the gastrocnemius muscle (Table 2).
Table 2Summary of radiological presentation, surgical management and outcomes.
Patient
ABI
PST
Radiological evaluation
T
A
MRI
Group
Type
Surgical management
1 year patency: 100% 5 year patency: 84%
1
0.4
—
T + A
+
+
NP
Ex
II
MTD + FPT
36 mo thrombosis
2
0.8
—
T + A
—
+
NP
Lim
II
MTD + PP
—
3
0.3 0.9
— —
T + A + MRI T + A + MRI
+ +
+ +
— —
Ex Ex
VI VI
MTD + FPT MTD + PPT
24 mo thrombosis 38 mo thrombosis
4
0.8
—
T + A
+
+
NP
Lim
I
MTD + PP
—
5
0.8
+
T + MRI
+
NP
+
Myo
II
MTD
—
6
0.9
—
T + A
+
+
NP
Lim
I
PP
30 mo stenosis
7
0.9
+
T + MRI
—
NP
+
Myo
II
MTD
—
8
1.1 0.8
— —
T + MRI T + MRI
— —
NP NP
+ +
Lim Lim
II II
MTD + PP MTD + PP
— —
9
0.9
—
T + A
+
+
NP
Lim
III
MTD + PP
—
10
1.0
—
T + MRI
—
NP
+
Lim
II
MTD + PP
—
11
1.1
—
T + A
+
+
NP
Lim
III
MTD + PP
—
12
0.9
+
T + MRI
—
NP
+
Myo
II
MTD
—
13
0.8 0.9
— —
T + MRI T + MRI
+ +
NP NP
+ —
Lim Lim
II II
MTD + PP PP
— —
14
0.8
+
T + MRI
—
NP
+
Myo
II
MTD
—
15
0.9 1.0
+ +
T + MRI T + MRI
— —
NP NP
+ +
Lim Lim
II II
MTD + PP MTD + PP
— —
16
1.1 1.0
— —
T + A T + A
+ +
+ +
NP NP
Ex Ex
II II
MTD + FPT MTD + FP
51 mo thrombosis —
17
0.3 1.0
— +
T + MRI T + MRI
— —
NP NP
+ +
Lim Lim
I I
MTD + PP MTD + PP
— —
18
0.3 1.1
— —
T + MRI T + MRI
— —
NP NP
+ +
Lim Lim
II II
MTD + PP MTD + PP
— —
Note. ABI = ankle brachial index; PST = positional stress test; A = angiography; T = computed tomography angiography; MRI = magnetic resonance imaging; NP = not performed; MTD = musculo-tendinous division; FPT = femoro-posterior tibial bypass; PP = popliteo-popliteal interposition; PPT = popliteo-posterior tibial bypass; FP = femoro-popliteal bypass; Lim = lesion limited to the popliteal artery; Ex = lesion extending beyond the popliteal artery; Myo = musculo-tendinous division without vascular reconstruction.
Based on the radiological findings, the popliteal artery was compressed but undamaged in 4 limbs (16%), and damaged in 21, with lesions limited to the popliteal artery in 16 limbs (64%) and thrombotic occlusions extending beyond the popliteal artery in five limbs (20%). When the lesion extended beyond the popliteal artery, it extended up to the femoral artery in one case and down to the tibial vessels in four cases (Table 3).
Table 3Pre-operative parameters according to the extent of the lesion.
Variable
Myotomy (4 patients, 4 limbs)
Limited lesion (11 patients, 16 limbs)
Extensive damage (3 patients, 5 limbs)
p
Median (range) age (y)
36 (32–45)
35 (19–49)
37 (15–45)
.66
Male
4 (100)
10 (91)
3 (100)
.71
Bilateral
0 (0)
5 (45)
2 (67)
.89
Hypertension
1 (25)
1 (9)
1 (33)
.70
Diabetes mellitus
0 (0)
1 (9)
0 (0)
.59
Dyslipidemia
0 (0)
0 (0)
0 (0)
NA
Active smoking
1 (25)
4 (36)
1 (33)
.78
Obesity
0 (0)
0 (0)
0 (0)
NA
Sport practice
2 (50)
6 (54)
1 (33)
.43
Median (range) evolution of length (mo)
13 (6–18)
15 (2–48)
10 (1–24)
.67
Claudication
3 (75)
14 (87)
3 (60)
.39
Rest pain
1 (25)
2 (12)
1 (20%)
.79
Tissue lesion
0 (0)
0 (0)
1 (20)
.13
Mean ABI (median, IQR)
0.85 (0.85, 0.10)
0.86 (0.90, 0.20)
0.74 (0.90, 0.70)
.76
Note. Data are n (%) unless otherwise indicated. NA = not applicable; IQR = interquartile range; ABI = ankle brachial index.
Regarding PAES classification there were four (16%), 17 (68%), 2 (8%), and 2 (8%) type I, II, III, and VI PAES, respectively (Table 3). The patients with bilateral PAES had the same type of PAES for each limb: one patient had type I (case 17), five patients had type II (cases 8, 13, 15, 16, and 18), and one patient had type VI (case 3) (Table 2).
Surgical management
Procedures consisted of a musculo-tendinous division without arterial reconstruction in the four limbs associated with a compressed but undamaged popliteal artery.
In the 16 limbs with lesions confined to the popliteal artery, procedures consisted of 16 interpositions of the damaged popliteal artery through 14 posterior approaches and two medial approaches. Musculo-tendinous division was performed in 14 limbs.
In the five limbs with the lesions extended beyond the popliteal artery, treatment consisted of one below knee femoro-popliteal bypass, three femoro-posterior tibial bypasses, and one popliteo-posterior tibial bypass, all through medial approaches. Musculo-tendinous division was performed in all five limbs (Table 2).
Great saphenous vein could be harvested in all patients that required interposition or bypass, as pre-operative Duplex ultrasound vein evaluation reported adequate caliber.
Thirty day mortality and morbidity
There was no mortality. Morbidity included post-operative hematoma that did not require re-intervention in two patients (cases 4 and 12). No other morbidity was recorded.
Five year patency
There was no loss to follow up. Mean follow up was 82 months (median 81; IQR 43). Five year patency was 84% (Fig. 3). Graft occlusion occurred in four limbs in three patients respectively, at 24, 36, 38, and 51 months after surgery (cases 1, 3, and 16). No patient required amputation following graft occlusion.
During follow up, there was one proximal graft anastomotic stenosis 30 months after surgery (case 6). No adjunctive procedure was performed in this patient, as he was asymptomatic and stenosis was <40%. In patients that underwent musculo-tendinous division alone no late stenosis of the popliteal artery was seen (Table 2).
Graft patency according to the extent of initial lesions
Comparison between the following three groups of patients showed no difference in terms of pre-operative parameters (Table 1): (1) patients that underwent myotomy alone; (2) patients that underwent surgery for lesions confined to the popliteal artery; and (3) patients that underwent surgery for lesions extending beyond the popliteal artery.
Five year patency in patients treated with musculo-tendinous division alone for compressed popliteal artery was 100%. The same applied to patients who underwent surgery for lesions limited to the popliteal artery. Five year graft patency in patients who presented lesions extending beyond the popliteal artery was 20% (p < .01).
Discussion
The main findings of this retrospective study are that long-term outcomes of surgical procedures in the setting of PAES are satisfactory. Outcomes might be better when the extent of the lesion is limited to the popliteal artery than when more extensive.
There are only a few publications reporting the long-term outcomes of the surgical treatment of PAES. As a rare and underestimated condition, reports of PAES over the last 10 years have been limited to a number of retrospective, single center small series.
The authors concluded that outcomes of PAES surgery are good, and that limb loss is a rare event because the arterial occlusion in PAES is a slow and chronic process allowing collaterals to develop. However, among the 49 surgical procedures, 33 consisted of a simple release of the popliteal artery, without any vascular reconstruction. Recently, Igari et al. evaluated the long-term outcomes of PAES surgical treatment with a retrospective study of 24 patients (29 limbs).
Among the 29 limbs, 25 required both revascularization and musculo-tendinous division. The authors reported 1 and 5 year patency rates of 96.3% and 91.9%, respectively.
To the best of the authors' knowledge only two studies have investigated longer term outcomes, with a 10 year patency of 100% in both cases: Yamamoto et al. included 16 patients (19 limbs),
The authors thus highlighted the need for early referral to a vascular surgeon for early diagnosis and treatment, especially in this population of young patients.
One important finding of this study is that the extent of the lesions beyond the popliteal artery seems to be associated with lower patency. In the authors' experience, 5 year patency of lesions extended beyond the popliteal artery was 20%. To understand these poor results, there are three possible explanations. The first is that diagnosis was made at an advanced stage because of late presentation or misdiagnosis. Di Marzo et al. reported that a vascular reconstruction was more often required when PAES was diagnosed at a late stage, reporting that limbs that underwent musculo-tendinous division alone showed better long-term patency than limbs that required vascular reconstruction.
Kim et al. also reported the durability of short segment popliteal interposition grafting with autologous vein, and showed that the durability of longer segment reconstructions was limited.
The second explanation could be that these patients may not only have proximal thrombotic occlusions, but also distally affected vascular beds, and this could be the reason for mid-term or late occlusions. The third explanation may be that vascular reconstruction of extensive lesions was performed in the setting of functional PAES in two limbs. Functional PAES is related to hypertrophy of the medial head of the gastrocnemius muscle with popliteal artery occlusion during contraction. It is perhaps the most challenging treatment.
Functional PAES characterization and the decision to treat may be confusing, particularly as non-invasive investigations such as ABI and CTA may be abnormal in a significant proportion of asymptomatic individuals.
In current study, the majority of patients referred for PAES needed vascular reconstruction at the time of presentation and only a few underwent myotomy alone. This highlights not only the need for early treatment, but also the evidence to take into account the possible associated deterioration of the downstream vascular bed at the time of presentation. Even though the arterial degradation in PAES is slow and the chronic process allows collateral development, it results in severe arterial wall destruction, which depends on the degree and duration of compression, and the magnitude of the forces exerted on the popliteal artery.
Unlike atherosclerosis, entrapment features neo-vascularization, inflammatory cell infiltrate, and vessel wall disruption, stimulating fibrosis and collagenization. This explains why distal emboli may develop as a consequence of focal thrombus formation at the site of entrapment or from popliteal aneurysm formation.
However, entrapment can also cause chronic irritation of sensory nerves located in the popliteal artery adventitia and can thereby lead to sympathetic-excitation and vascular bed degeneration.
Therefore, a new problem is being faced—would it make sense to operate preventively on the asymptomatic contralateral limb in order to avoid the deterioration of the underlying vascular bed and the need for vascular reconstruction at the time of presentation? The question still remains open and no recommendation has been proposed.
In addition, there is no standardized imaging modality strategy. Clinical examination is usually unreliable in the diagnosis of PAES, as physical examination may suggest an occluded popliteal segment with absent pulses only when the disease is advanced. The PST does not appear to be as reliable a clinical screening tool as once thought.
However, if demonstrated, it should raise suspicion. Various imaging modalities have since been performed, including Duplex ultrasonography, CTA, conventional arteriography, and/or MRI, highlighting that diagnosis can be challenging. As PAES is an uncommon pathology without a standardized imaging modality strategy, it is likely that too many imaging modalities are performed. However, early and correct diagnosis is crucial in these young patients, which can explain the number of imaging modalities used. Adequate pre-operative investigation is crucial in order to provide the best surgical management. The best surgical approach is a posterior S-shaped incision in the popliteal fossa, which enables complete exposure of the popliteal artery and its surrounding structures. Ideally, if the condition is recognized early and the vessel remains undamaged, simple release of the popliteal artery can be performed. When the artery is damaged, revascularization can be carried out using the posterior approach, affording good access to the artery and other structures of the popliteal fossa, facilitating both confirmation of the diagnosis and popliteal artery release. The medial approach to the popliteal artery is better for longer lesions. However, the technical disadvantage of this approach is that complete exposure of the popliteal artery and its relationship to the surrounding muscle is difficult and can lead to the underlying entrapment being missed. This highlights the need for adequate pre-operative investigation in order to document anatomic abnormalities clearly and propose the best treatment option for the patient.
This study suffers from several limitations. First, it is a retrospective study, generating the bias linked to retrospective data analysis, even though a lot of the data were collected prospectively. The number of patients included is relatively small, but because PAES is a rare condition it is difficult to obtain a large number of patients. Furthermore, because of the small number of patients, a complex statistical analysis cannot be performed, giving less validity to the findings. Study quality is of course, insufficient to allow for robust conclusions to be drawn with regard to recommending any one particular operative procedure. This highlights the need for prospectively collected data with pre-defined inclusion criteria, outcome measures, follow up protocols, and standardized reporting criteria.
Conclusion
The outcomes of surgical procedures performed in the setting of PAES can be considered satisfactory. Prospective studies, with predefined reporting criteria and standardized long-term protocols, are mandatory.
Conflict of Interest
None.
Funding
None.
References
Stuart T.P.
Note on a variation in the course of the popliteal artery.
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