DOI: 10.1148/rg.242035117
RadioGraphics 2004;24:467-479
© RSNA, 2004
Popliteal Artery Disease: Diagnosis and Treatment1
Lonnie B. Wright, MD,
W. Jean Matchett, MD,
Carlos P. Cruz, MD,
Charles A. James, MD,
William C. Culp, MD,
John F. Eidt, MD and
Timothy C. McCowan, MD
1 From the Departments of Radiology and Surgery, University of Arkansas for Medical Sciences, 4301 W Markham St, Slot 556, Little Rock, AR 72205. Presented as an education exhibit at the 2002 RSNA scientific assembly. Received April 28, 2003; revision requested July 8 and received September 29; accepted October 1. All authors have no financial relationships to disclose. Address correspondence to W.J.M. (e-mail: matchettwjean@uams.edu).
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Abstract
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The popliteal artery is a relatively short vascular segment but is affected by a unique set of pathologic conditions. These conditions, which may be common throughout the arterial system or exclusive to the popliteal artery, include atherosclerosis, popliteal artery aneurysm, arterial embolus, trauma, popliteal artery entrapment syndrome, and cystic adventitial disease. The clinical manifestations, imaging appearances, and treatment options associated with these pathologic conditions differ significantly. Consequently, the radiologist should be familiar with these conditions to direct imaging for accurate diagnosis and treatment and to prevent loss of limb.
© RSNA, 2004
Index Terms: Aneurysm, popliteal, 924.731 • Arteries, extremities, 924.721, 924.731, 924.751, 924.92 • Arteries, popliteal, 924.721, 924.731, 924.751, 924.92 • Arteries, stenosis or obstruction, 924.41, 924.721 • Arteries, thrombosis, 924.751 vol Arteriosclerosis, 924.721 • Embolism, 924.77 Grafts, 924.452
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LEARNING OBJECTIVES
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After reading this article and taking the test, the reader will be able to:
- List the various diseases that can affect the popliteal artery.
- Discuss the differential diagnosis of these diseases as developed on the basis of clinical findings.
- Describe optimal management of popliteal artery disease.
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Introduction
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The popliteal artery is located behind the knee in the popliteal fossa and is a direct extension of the superficial femoral artery after it passes through the adductor hiatus, an opening in the tendinous slip of the great adductor muscle of the thigh. The popliteal artery lies posterior to the femur and anterior to the popliteal vein. The popliteal artery and vein are normally located between the two heads of the gastrocnemius muscle (Fig 1). Abnormalities in this relationship can produce popliteal artery entrapment syndrome (PAES). In the region of the knee, the popliteal artery gives off genicular and sural branches, eventually dividing into the anterior tibial artery and the tibioperoneal trunk. The tibioperoneal trunk further subdivides into the posterior tibial and peroneal arteries. The proximity of the popliteal artery to the distal femur makes it susceptible to injury when the distal femur is fractured or the knee is dislocated.
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Figure 1a. Normal anatomy. (a) Axial T1-weighted magnetic resonance (MR) image demonstrates the popliteal artery (white arrow), popliteal vein (black arrow), and medial (white *) and lateral (black *) heads of the gastrocnemius muscle. (b) Arteriogram demonstrates the popliteal artery (*), sural arteries (black arrows), genicular arteries (white arrows), anterior tibial artery (white arrowhead), tibioperoneal trunk (black arrowhead), peroneal artery (white arrow with crossbar), and posterior tibial artery (black arrow with crossbar).
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Figure 1b. Normal anatomy. (a) Axial T1-weighted magnetic resonance (MR) image demonstrates the popliteal artery (white arrow), popliteal vein (black arrow), and medial (white *) and lateral (black *) heads of the gastrocnemius muscle. (b) Arteriogram demonstrates the popliteal artery (*), sural arteries (black arrows), genicular arteries (white arrows), anterior tibial artery (white arrowhead), tibioperoneal trunk (black arrowhead), peroneal artery (white arrow with crossbar), and posterior tibial artery (black arrow with crossbar).
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Clinical signs and symptoms of diseases that affect the popliteal artery overlap, but the affected patient populations are often distinct. Understanding this fact can aid the radiologist in directing imaging for diagnosis and treatment. In this article, we discuss and illustrate the clinical manifestations, imaging appearances, differential diagnosis, and treatment options in a variety of diseases that affect the popliteal artery, including atherosclerosis, aneurysm, traumatic injury, arterial embolus, PAES, and cystic adventitial disease (CAD).
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Atherosclerosis
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Atherosclerosis is the leading cause of morbidity and mortality in the United States and is the most common cause of popliteal artery occlusion or stenosis. The pathogenesis of atherosclerosis is well established. Endothelial injury initiates a process whereby overproduction of cellular mediators eventually produces fibrotic plaque. This plaque may calcify, fracture, ulcerate, hemorrhage, and ultimately limit blood flow or cause thrombosis of the vessel. Risk factors for atherosclerosis include smoking, diabetes, advancing age, hyperlipidemia, hypertension, male gender, and a family history of the disease.
Patients can present with a variety of symptoms depending on the degree of disease (Table 1). Single-level disease commonly manifests as intermittent claudication. Multilevel disease will manifest with more severe ischemic symptoms of rest pain and tissue loss. At physical examination, the patient will have a decreased or absent pulse at or below levels of significant disease. Bruits may be auscultated at levels of significant stenosis.
Noninvasive arterial studies include color duplex ultrasonography (US) and an ABI with segmental lower-extremity arterial pressure readings or pulse volume recordings. These studies are cost effective and can help localize and determine the severity of lower-extremity arterial disease. MR angiography can provide noninvasive, arteriographic localization of disease, but at a greater cost. Gadolinium-enhanced three-dimensional time-of-flight MR angiography can provide diagnostic accuracy similar to that of standard contrast material–enhanced angiography. High-quality imaging requires a certain level of expertise and is best performed with a stepping table (2) or sequential imaging with multiple injections (3). There are still problems with variable runoff times and image degradation at the trifurcation due to venous filling. Conventional angiography is usually performed when endovascular or surgical intervention is required.
Atherosclerosis will appear at angiography as irregularity in the vessel lumen in the form of stenosis or occlusion (Fig 2). When atherosclerosis is the cause of popliteal artery stenosis or occlusion, similar vessel irregularity is found at other locations in the peripheral runoff. Over time, with popliteal artery occlusion or significant stenosis, collateral vessels will reconstitute distal runoff. Commonly, branches of the deep femoral artery will provide collateral vessels for the more distal popliteal or trifurcation vessels via sural or genicular branches.
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Figure 2. Arteriogram demonstrates complete occlusion of the right popliteal artery by atherosclerosis, with collateral reconstitution of the posterior tibial artery. Many other areas of irregularity and stenosis are seen on both sides. The patient did not undergo treatment.
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Interventional therapy for lower-extremity atherosclerotic disease commonly involves percutaneous transluminal angioplasty (PTA), thrombolytic infusion, and, less often, stent placement. Pentecost et al (4), in conjunction with the American Heart Association task force, designed a classification scheme for popliteal and superficial femoral artery disease to help decide whether treatment should consist of PTA or surgery (Table 2). Since that time, the SCVIR (Society of Cardiovascular and Interventional Radiology) Transluminal Arterial Revascularization (STAR) registry (5) analyzed 219 limbs in which PTA of the femoropopliteal artery had been performed. In the STAR registry, category 1 lesions had patency rates of 87% at 36 months, and category 2 and 3 lesions had a patency rate of 69% and 67%, respectively. These patency rates are similar to those achieved with bypass surgery (Fig 3).
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Figure 3a. (a) Arteriogram shows a high-grade focal lesion of the popliteal artery at the adductor hiatus (arrow). (b) Arteriogram obtained after angioplasty demonstrates good treatment results.
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Figure 3b. (a) Arteriogram shows a high-grade focal lesion of the popliteal artery at the adductor hiatus (arrow). (b) Arteriogram obtained after angioplasty demonstrates good treatment results.
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Thrombolytic therapy can be used to treat acute and subacute occlusions of the popliteal artery due to underlying stenosis. Thrombolytic therapy is most successful if initiated within 2 weeks after thrombosis (6). Therapy is initiated with a catheter with multiple side holes that is positioned across the occluded segment. Constant infusion of a lytic agent is usually required for 8–36 hours with intermittent follow-up angiography. Stenoses are often uncovered, which can then be treated with PTA.
Primary stent placement in the popliteal and superficial femoral arteries is not indicated because the long-term patency rates are poor (7). Stent placement in the popliteal artery should be reserved for cases of failed PTA. Self-expanding stents should be used because of the superficial location of the popliteal artery and concerns about extrinsic compression. Surgical therapies generally consist of bypass grafting (Fig 4) and, less often, endarterectomy and patch angioplasty. When the popliteal artery is bypassed below the knee joint, a vein graft is superior to a synthetic graft.
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Figure 4a. (a) Arteriogram shows a prior bypass (vein) graft connecting the femoral artery to the popliteal artery below the knee (arrowhead). Note the stenosis of the distal vein graft anastomosis (arrow). (b) Arteriogram obtained after angioplasty shows that the treatment was successful.
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Figure 4b. (a) Arteriogram shows a prior bypass (vein) graft connecting the femoral artery to the popliteal artery below the knee (arrowhead). Note the stenosis of the distal vein graft anastomosis (arrow). (b) Arteriogram obtained after angioplasty shows that the treatment was successful.
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Popliteal Artery Aneurysms
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Generally, aneurysms can be categorized as either true or false. True aneurysms occur when all layers of the arterial wall are abnormally dilated. False aneurysms (pseudoaneurysms) are due to a defect in the arterial wall related to trauma or (mycotic) infection. Trauma may be related to iatrogenic injury due to surgery or intervention.
The popliteal artery is considered aneurysmal if its diameter exceeds 0.7 cm. Aneurysms may rarely be associated with connective tissue diseases such as Marfan syndrome or Ehlers-Danlos syndrome or, even more rarely, with pregnancy. Almost all true aneurysms are nonspecific. Historically, the nonspecific form of aneurysmal disease that affects the abdominal aorta and the iliac, femoral, and popliteal arteries has been described as "atherosclerotic." Risk factors associated with atherosclerotic disease are also associated with nonspecific aneurysms. However, atherosclerotic disease and these risk factors incompletely define the cause of these aneurysms, which appears to be multifactorial.
True aneurysms of the popliteal artery are the most common peripheral arterial aneurysms. Popliteal artery aneurysms (PAAs) are relatively uncommon compared with abdominal aortic aneurysms (AAAs), but recent studies have identified an increase in the prevalence of PAAs that may be due to greater access to imaging modalities such as US. Consequently, reports vary as to the ratio of PAAs to AAAs, which ranges from 1:8 to 1:23 (8,9). PAAs are associated with aneurysms in other locations. An AAA is present in 30%–50% of patients with a PAA. In contrast, PAAs are present in only about 10%–14% of patients with AAAs (9,10). PAAs are bilateral in 50%–70% of cases. These associations have important implications. In patients with a PAA, it is important to look for AAAs and a contralateral PAA. PAAs are usually found during the 6th and 7th decades of life and have a strong male predilection, with a male:female ratio ranging from 10:1 to 30:1 in published reports (10–12).
It is very important to diagnose PAAs because of the risk of limb-threatening thrombotic complications. About 45% of patients with PAAs are asymptomatic at the time of diagnosis. Symptomatic patients present with lower-extremity ischemia, which can manifest as claudication, rest pain, or severe ischemia associated with thrombosis or embolization (Fig 5). In general, US is the most commonly used and the best imaging modality for diagnosing PAAs. US can help determine the presence and patency of an aneurysm and whether the aneurysm contains thrombus. Color Doppler US also helps distinguish an aneurysm from a popliteal mass such as a Baker cyst (Fig 6). Conventional angiography may not help identify PAA, especially if the artery is occluded. MR imaging may be helpful in that it will delineate the aneurysmal sac and mural thrombus.
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Figure 5a. Unsubtracted (a) and subtracted (b) digital arteriograms obtained in an elderly man with bilateral popliteal aneurysms show the right popliteal artery (arrow in a), anterior tibial artery (arrowhead), and tibioperoneal trunk (arrow in b). The right-sided aneurysm was thrombosed, and the patient underwent embolectomy and bypass surgery.
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Figure 5b. Unsubtracted (a) and subtracted (b) digital arteriograms obtained in an elderly man with bilateral popliteal aneurysms show the right popliteal artery (arrow in a), anterior tibial artery (arrowhead), and tibioperoneal trunk (arrow in b). The right-sided aneurysm was thrombosed, and the patient underwent embolectomy and bypass surgery.
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Figure 6a. (a, b) On color Doppler US images obtained in a 55-year-old man with bilateral popliteal aneurysms that were diagnosed with US, the right-sided aneurysm is patent (arrow in a) and the left-sided aneurysm is occluded (arrowheads in b). (c) Angiogram of the left lower extremity shows typically tortuous vasculature with atherosclerotic changes.
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Figure 6b. (a, b) On color Doppler US images obtained in a 55-year-old man with bilateral popliteal aneurysms that were diagnosed with US, the right-sided aneurysm is patent (arrow in a) and the left-sided aneurysm is occluded (arrowheads in b). (c) Angiogram of the left lower extremity shows typically tortuous vasculature with atherosclerotic changes.
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Figure 6c. (a, b) On color Doppler US images obtained in a 55-year-old man with bilateral popliteal aneurysms that were diagnosed with US, the right-sided aneurysm is patent (arrow in a) and the left-sided aneurysm is occluded (arrowheads in b). (c) Angiogram of the left lower extremity shows typically tortuous vasculature with atherosclerotic changes.
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PAAs can be complicated by thrombosis, distal embolization of thrombotic material, and, rarely, rupture. Studies have shown that complications occur in 18%–31% of such aneurysms that were not corrected surgically (13). Thrombolytic therapy is often required in patients who present with acute thrombosis to recanalize the distal popliteal and trifurcation vessels as targets for bypass surgery (Fig 7). Despite the thrombus burden present within popliteal aneurysms, thrombolytic therapy is very successful in patients who can withstand an additional period of ischemia (14).
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Figure 7a. (a) Arteriogram obtained in a 65-year-old man who presented with acute ischemia of the left lower extremity shows occlusion of the left popliteal artery and aneurysmal dilatation of the right popliteal artery. (b) Computed tomographic scan depicts a coexisting AAA with mural thrombus (*) and a partially open lumen (arrow). Thrombolysis of the left popliteal artery and trifurcation vessels was performed. (c, d) Postlysis images show patency of the popliteal artery (c) and trifurcation vessels (d), which includes the tibioperoneal trunk (*), anterior tibial artery (arrow), and posterior tibial artery (arrowhead). The patient underwent bypass surgery on both popliteal arteries.
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Figure 7b. (a) Arteriogram obtained in a 65-year-old man who presented with acute ischemia of the left lower extremity shows occlusion of the left popliteal artery and aneurysmal dilatation of the right popliteal artery. (b) Computed tomographic scan depicts a coexisting AAA with mural thrombus (*) and a partially open lumen (arrow). Thrombolysis of the left popliteal artery and trifurcation vessels was performed. (c, d) Postlysis images show patency of the popliteal artery (c) and trifurcation vessels (d), which includes the tibioperoneal trunk (*), anterior tibial artery (arrow), and posterior tibial artery (arrowhead). The patient underwent bypass surgery on both popliteal arteries.
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Figure 7c. (a) Arteriogram obtained in a 65-year-old man who presented with acute ischemia of the left lower extremity shows occlusion of the left popliteal artery and aneurysmal dilatation of the right popliteal artery. (b) Computed tomographic scan depicts a coexisting AAA with mural thrombus (*) and a partially open lumen (arrow). Thrombolysis of the left popliteal artery and trifurcation vessels was performed. (c, d) Postlysis images show patency of the popliteal artery (c) and trifurcation vessels (d), which includes the tibioperoneal trunk (*), anterior tibial artery (arrow), and posterior tibial artery (arrowhead). The patient underwent bypass surgery on both popliteal arteries.
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Figure 7d. (a) Arteriogram obtained in a 65-year-old man who presented with acute ischemia of the left lower extremity shows occlusion of the left popliteal artery and aneurysmal dilatation of the right popliteal artery. (b) Computed tomographic scan depicts a coexisting AAA with mural thrombus (*) and a partially open lumen (arrow). Thrombolysis of the left popliteal artery and trifurcation vessels was performed. (c, d) Postlysis images show patency of the popliteal artery (c) and trifurcation vessels (d), which includes the tibioperoneal trunk (*), anterior tibial artery (arrow), and posterior tibial artery (arrowhead). The patient underwent bypass surgery on both popliteal arteries.
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It is currently recommended that asymptomatic PAAs be repaired unless surgery would put the patient at high risk. This recommendation is based on the high prevalence of complications regardless of the size of the aneurysm, the high amputation rate after complications develop, and the lower graft patency rate in patients who have experienced complications (9).
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Trauma
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The popliteal artery is susceptible to injury due to its proximity to the distal femur and knee joint. Anterior and posterior knee dislocations as well as fractures are often associated with popliteal artery injury. Popliteal artery occlusion is seen in 30%–50% of patients with complete knee dislocation (15). In today’s society, such injuries are most commonly caused by motor vehicle accidents, but injury related to penetrating trauma is not uncommon. These traumatic injuries include laceration, dissection, occlusion, and posttraumatic pseudoaneurysm formation (Fig 8). Trauma affecting the popliteal artery and vein will occasionally produce an arteriovenous fistula (Fig 9).
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Figure 8a. (a) Angiogram obtained in a 16-year-old girl, who sustained injury to the popliteal artery during arthroscopy, underwent bypass grafting (vein graft), and presented with an enlarging popliteal mass, shows a pseudoaneurysm (*) of the native popliteal artery (arrowhead) related to the iatrogenic injury. The vein graft is patent (arrows). (b) Angiogram obtained after coil embolization of the native popliteal artery distal and proximal to the pseudoaneurysm (*) demonstrates the coils (arrowhead) and the vein graft (arrow). (c) Final angiogram shows patency of the graft (arrows) and no filling of the aneurysm or native popliteal artery. Color duplex US was used to follow up the aneurysm. (d) US image obtained 15 days later shows no flow and a shrinking aneurysmal sac. No further surgery was required.
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Figure 8b. (a) Angiogram obtained in a 16-year-old girl, who sustained injury to the popliteal artery during arthroscopy, underwent bypass grafting (vein graft), and presented with an enlarging popliteal mass, shows a pseudoaneurysm (*) of the native popliteal artery (arrowhead) related to the iatrogenic injury. The vein graft is patent (arrows). (b) Angiogram obtained after coil embolization of the native popliteal artery distal and proximal to the pseudoaneurysm (*) demonstrates the coils (arrowhead) and the vein graft (arrow). (c) Final angiogram shows patency of the graft (arrows) and no filling of the aneurysm or native popliteal artery. Color duplex US was used to follow up the aneurysm. (d) US image obtained 15 days later shows no flow and a shrinking aneurysmal sac. No further surgery was required.
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Figure 8c. (a) Angiogram obtained in a 16-year-old girl, who sustained injury to the popliteal artery during arthroscopy, underwent bypass grafting (vein graft), and presented with an enlarging popliteal mass, shows a pseudoaneurysm (*) of the native popliteal artery (arrowhead) related to the iatrogenic injury. The vein graft is patent (arrows). (b) Angiogram obtained after coil embolization of the native popliteal artery distal and proximal to the pseudoaneurysm (*) demonstrates the coils (arrowhead) and the vein graft (arrow). (c) Final angiogram shows patency of the graft (arrows) and no filling of the aneurysm or native popliteal artery. Color duplex US was used to follow up the aneurysm. (d) US image obtained 15 days later shows no flow and a shrinking aneurysmal sac. No further surgery was required.
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Figure 8d. (a) Angiogram obtained in a 16-year-old girl, who sustained injury to the popliteal artery during arthroscopy, underwent bypass grafting (vein graft), and presented with an enlarging popliteal mass, shows a pseudoaneurysm (*) of the native popliteal artery (arrowhead) related to the iatrogenic injury. The vein graft is patent (arrows). (b) Angiogram obtained after coil embolization of the native popliteal artery distal and proximal to the pseudoaneurysm (*) demonstrates the coils (arrowhead) and the vein graft (arrow). (c) Final angiogram shows patency of the graft (arrows) and no filling of the aneurysm or native popliteal artery. Color duplex US was used to follow up the aneurysm. (d) US image obtained 15 days later shows no flow and a shrinking aneurysmal sac. No further surgery was required.
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Figure 9. Arterial-phase angiogram of the left lower extremity demonstrates early venous filling. A gunshot wound had produced an arteriovenous fistula of the proximal popliteal artery (white arrow) and popliteal vein (black arrow).
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Diagnosis of popliteal artery trauma requires a high degree of suspicion on the part of the clinician. Any traumatic injury to the knee should prompt a thorough arterial examination of the affected extremity. A knee can be dislocated and subsequently relocated prior to presentation. Furthermore, the clinical findings can be misleading: The presence of distal pulses does not rule out injury to the popliteal artery, nor does normal distal capillary refill (16–18). Ultimately, a patient with knee dislocation may require arteriography to rule out injury to the popliteal artery. The angiographic appearance may vary from intimal dissection to complete occlusion of the artery (Fig 10).
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Figure 10. Arteriogram obtained in a patient with a dislocated knee from a motor vehicle accident, absent pulses, and present but abnormal Doppler signals shows nonfilling of the midpopliteal artery. Intimal injury was found at surgery and was treated with bypass grafting.
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Patients with severe trauma and obvious arterial injury at clinical examination will usually proceed to surgery. Surgical treatment involves bypass grafting or patch angioplasty. Percutaneous treatment currently plays no role in management. Again, timely diagnosis and treatment is critical to decrease morbidity and obviate limb amputation (16).
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Arterial Embolus
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The popliteal artery, like any other peripheral artery, can be affected by embolism. Macroemboli have a tendency to lodge in the popliteal artery at the bifurcation into the tibioperoneal trunk and anterior tibial artery. An embolus in the lower extremities most often has a cardiac source. Other sources include aortic aneurysms and proximal arterial plaque or ulceration. Regardless of the source, acute arterial embolism almost always requires urgent treatment.
Patients with arterial embolism present with acute symptoms. The five cardinal signs and symptoms of arterial ischemia are pain, pallor, pulselessness, paresthesia, and paralysis. With an occluding embolus, the patient will experience acute rest pain. The lower leg and foot will appear pale and have no pulses. If the condition is left untreated, it can progress to paresthesia and paralysis. Noninvasive arterial examination may be performed prior to angiography. With acute occlusion, there may be a total lack of Doppler signals at the ankle; thus, an ABI cannot be obtained. Color duplex US can also be used to depict thrombus, but the patient will usually proceed to angiography due to the acute clinical presentation. Thrombus in the popliteal artery appears as a complete angiographic occlusion producing the classic "meniscus sign," a filling defect or abrupt vessel cutoff (Fig 11).
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Figure 11a. (a) Angiogram obtained in a 52-year-old patient who presented with acute bilateral ischemia of the lower extremities shows abrupt occlusion of both popliteal arteries (arrows). The appearance of the arteries elsewhere was normal. Embolus, PAES, and CAD were considered as possible causes. Catheter-directed thrombolysis of the right popliteal artery was performed. (b) Follow-up angiogram shows patency of the right popliteal artery (*), anterior tibial artery (black arrow), tibioperoneal trunk (white arrow), posterior tibial artery (black arrowhead), and peroneal artery (white arrowhead). (c) Angiogram obtained more distally shows patency of the trifurcation vessels. (d) Angiogram of the left lower extremity reveals spontaneous recanalization of the left popliteal artery (*) and anterior tibial artery (arrowhead) due to the systemic effects of thrombolysis and anticoagulation therapy. Arrow indicates an embolus in the tibioperoneal trunk, which was thought to have resulted from atrial fibrillation.
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Figure 11b. (a) Angiogram obtained in a 52-year-old patient who presented with acute bilateral ischemia of the lower extremities shows abrupt occlusion of both popliteal arteries (arrows). The appearance of the arteries elsewhere was normal. Embolus, PAES, and CAD were considered as possible causes. Catheter-directed thrombolysis of the right popliteal artery was performed. (b) Follow-up angiogram shows patency of the right popliteal artery (*), anterior tibial artery (black arrow), tibioperoneal trunk (white arrow), posterior tibial artery (black arrowhead), and peroneal artery (white arrowhead). (c) Angiogram obtained more distally shows patency of the trifurcation vessels. (d) Angiogram of the left lower extremity reveals spontaneous recanalization of the left popliteal artery (*) and anterior tibial artery (arrowhead) due to the systemic effects of thrombolysis and anticoagulation therapy. Arrow indicates an embolus in the tibioperoneal trunk, which was thought to have resulted from atrial fibrillation.
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Figure 11c. (a) Angiogram obtained in a 52-year-old patient who presented with acute bilateral ischemia of the lower extremities shows abrupt occlusion of both popliteal arteries (arrows). The appearance of the arteries elsewhere was normal. Embolus, PAES, and CAD were considered as possible causes. Catheter-directed thrombolysis of the right popliteal artery was performed. (b) Follow-up angiogram shows patency of the right popliteal artery (*), anterior tibial artery (black arrow), tibioperoneal trunk (white arrow), posterior tibial artery (black arrowhead), and peroneal artery (white arrowhead). (c) Angiogram obtained more distally shows patency of the trifurcation vessels. (d) Angiogram of the left lower extremity reveals spontaneous recanalization of the left popliteal artery (*) and anterior tibial artery (arrowhead) due to the systemic effects of thrombolysis and anticoagulation therapy. Arrow indicates an embolus in the tibioperoneal trunk, which was thought to have resulted from atrial fibrillation.
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Figure 11d. (a) Angiogram obtained in a 52-year-old patient who presented with acute bilateral ischemia of the lower extremities shows abrupt occlusion of both popliteal arteries (arrows). The appearance of the arteries elsewhere was normal. Embolus, PAES, and CAD were considered as possible causes. Catheter-directed thrombolysis of the right popliteal artery was performed. (b) Follow-up angiogram shows patency of the right popliteal artery (*), anterior tibial artery (black arrow), tibioperoneal trunk (white arrow), posterior tibial artery (black arrowhead), and peroneal artery (white arrowhead). (c) Angiogram obtained more distally shows patency of the trifurcation vessels. (d) Angiogram of the left lower extremity reveals spontaneous recanalization of the left popliteal artery (*) and anterior tibial artery (arrowhead) due to the systemic effects of thrombolysis and anticoagulation therapy. Arrow indicates an embolus in the tibioperoneal trunk, which was thought to have resulted from atrial fibrillation.
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Options for treatment of acute embolism include systemic anticoagulation therapy, percutaneous thrombolytic therapy, surgical embolectomy, and mechanical thrombectomy. The degree of ischemia that the patient is experiencing will often dictate therapy. If the ischemia has progressed but is possibly reversible, surgical options might be more timely, considering the time it takes to perform thrombolysis. Thrombolytic therapy has proved to be effective, with minimal risk of hemorrhagic complications, and reduces the need for surgical procedures with similar limb salvage rates (6,19,20). Other interventional techniques involve mechanical thrombectomy devices that decimate or suction the thrombus (21,22). Treatment should be initiated within hours of the onset of symptoms for the best prognosis.
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Popliteal Artery Entrapment Syndrome
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The abnormal relationship of the popliteal artery to the gastrocnemius muscle was first described by a medical student, T. P. Anderson Stuart, in 1879 (23). It wasn’t until the 1960s that the term popliteal artery entrapment syndrome, or PAES, was first used (24). PAES is a developmental abnormality that results from an abnormal relationship of the popliteal artery to the gastrocnemius muscle or, rarely, an anomalous fibrous band or the popliteus muscle. The abnormal position causes deviation and compression of the artery. There are essentially four anatomic variants of PAES (Fig 12). Type V is any of the four anatomic variants that includes the popliteal vein (25).
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Figure 12. Drawings illustrate the classification scheme for PAES. In type I, the medial head of the gastrocnemius muscle is normal, and the popliteal artery is displaced medially around and beneath the muscle. In type II, the medial head of the gastrocnemius muscle arises from an abnormal lateral position. The popliteal artery descends normally but passes medial to and beneath the muscle. In type III, the popliteal artery is compressed by an abnormal slip of gastrocnemius muscle. In type IV, the popliteal artery is entrapped by a fibrous band or by the popliteus muscle. Type V is any of the four preceding types that includes the popliteal vein, and type VI is functional PAES (normal anatomy).
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Recently, a "functional" PAES has been described in patients with normal anatomy (type VI [Fig 12]). In such cases, compression of the popliteal artery may be due to an anatomically normal but hypertrophic muscle. This entity is usually seen in well-conditioned athletes.
The true prevalence of PAES is unknown. Patients are typically young (60% <30 years old), healthy males (15:1 male predilection) (25). Early reports cited a prevalence of 0.165% in young males entering military service (26), and a postmortem study found PAES in 3.5% of cases (27). PAES may be more common than previously recognized. In young athletes with calf claudication, 60% of cases may be due to PAES (28). Bilateral popliteal artery involvement has been reported in 22%–67% of presenting patients (29). Turnipseed (30) found that patients with functional PAES are younger than those with the anatomic types (mean age, 24 vs 43 years) and are more commonly female (60% vs 28% of cases). Patients with PAES usually present with calf claudication and, rarely, with ischemia due to thrombosis. At physical examination, these patients may have normal pulses that disappear or decrease with plantar flexion or dorsiflexion of the foot. In patients with PAES, resting ABIs will usually be normal, but ankle pressures will decrease with exercise. Duplex US may demonstrate stenosis at color imaging and increased velocities with the flexion maneuvers. MR imaging and MR angiography are valuable noninvasive studies because of their capacity to demonstrate the vessel lumen as well as the surrounding anatomy to help determine if the artery-muscle relationship is normal. Stress angiography (ie, angiography performed in the neutral position as well as with the foot in either dorsiflexion or plantar flexion to elicit the compression) is usually performed to confirm the diagnosis prior to surgery. Imaging commonly shows a normal arterial lumen with the foot in the relaxed position, with narrowing of the arterial lumen during stress maneuvers (Fig 13).
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Figure 13a. Stress angiography was performed in a 45-year-old woman who experienced calf claudication walking uphill but was otherwise healthy and a nonsmoker. (a) Angiogram obtained with the foot in a relaxed, neutral position demonstrates no stenosis of the popliteal artery. (b) Angiogram obtained with the foot in dorsiflexion shows stenosis of the artery (arrow). MR imaging was used to define the normal position of the artery relative to the muscle, and a diagnosis of functional PAES was made.
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Figure 13b. Stress angiography was performed in a 45-year-old woman who experienced calf claudication walking uphill but was otherwise healthy and a nonsmoker. (a) Angiogram obtained with the foot in a relaxed, neutral position demonstrates no stenosis of the popliteal artery. (b) Angiogram obtained with the foot in dorsiflexion shows stenosis of the artery (arrow). MR imaging was used to define the normal position of the artery relative to the muscle, and a diagnosis of functional PAES was made.
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If left untreated, PAES almost invariably progresses to permanent narrowing of the popliteal artery due to repeated microtrauma to the vessel, with subsequent fibrosis making the vessel susceptible to thrombosis (28). Surgical release of the muscle or tendon is the ultimate treatment in PAES types I–V (28). Interventional thrombolysis would be appropriate therapy for patients who present with occlusion due to PAES. Thrombolysis of the distal popliteal and runoff vessels can be very important prior to surgical correction. The affected segment of the popliteal artery is usually bypassed or replaced once thrombosis has developed due to fibrosis. There are no indications for angioplasty or stent placement in patients with PAES. In patients with functional PAES, myomectomy of the medial head of the gastrocnemius muscle can result in complete relief of symptoms but is recommended for patients with "discrete and typical symptoms" because narrowing of the popliteal artery with plantar flexion or dorsiflexion may occur in up to 50% of the general population (31).
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Cystic Adventitial Disease
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CAD occurs when mucoid cysts in the adventitia compress the popliteal artery. This entity was first described in 1947 by Atkins and Key (32) in a patient with CAD that affected the external iliac artery. Since then, there have been many case reports, usually involving young men with intermittent claudication in whom surgery revealed a mucoid cyst of the popliteal artery. A review by Jasinski et al (33) established that CAD occurs where large arteries are associated with joints. The popliteal artery is the most common location (85% of cases), but other investigators have reported involvement of the external iliac, common femoral, radial, and ulnar arteries. The cause of this disease is not completely known. Levien and Benn (34) discuss the four theories concerning the causes of CAD and the authors who have indicated support for each theory. These theories include (a) a myxomatous systemic degenerative condition associated with a systemic disease, (b) repeated trauma, (c) cysts arising from synovial ganglia that migrate into the adventitia, and (d) mucinous cysts arising from mucin-producing mesenchymal cell rests incorporated into the vessel wall during development (the theory favored by Levien and Benn).
CAD is rare, accounting for only 0.1% of vascular disease. Patients are usually men in their mid-40s who present with intermittent claudication. Claudication can have an acute onset but rarely manifests as rest pain. At physical examination, there is decrease or loss of pulses and, rarely, a popliteal bruit. The ABI will be decreased, and the segmental pressures or pulse volume recordings will indicate a pressure drop across the affected popliteal artery. Duplex US will depict an arterial stenosis with surrounding cysts, which contain no flow. These cysts appear as anechoic or hypoechoic masses in the wall of the vessel. The cysts can manifest as distinctive stenoses of the vessel lumen at angiography. If the cysts are concentric, the stenosis will have an "hourglass" appearance; if they are eccentric, the stenosis will demonstrate the classic "scimitar sign." Although conventional angiography has traditionally been the study of choice, it has recently been suggested that MR imaging is equal in diagnostic capability. MR imaging provides the most information (35). Cysts are hyperintense on T2-weighted MR images and have variable signal intensity on T1-weighted images because of the variable amount of mucoid material within the cysts. Compression of the popliteal artery produced by cysts can be seen on axial MR images (Fig 14) and angiographically with three-dimensional time-of-flight imaging.
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Figure 14a. A 42-year-old male runner presented with acute claudication of the left lower extremity and was initially thought to have popliteal entrapment. (a, b) Stress (a) and nonstress (b) angiograms depict a similar hourglass-shaped stenosis. (c-e) Sequential axial T2-weighted MR images reveal extensive compression of the popliteal artery by CAD (arrow).
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Figure 14b. A 42-year-old male runner presented with acute claudication of the left lower extremity and was initially thought to have popliteal entrapment. (a, b) Stress (a) and nonstress (b) angiograms depict a similar hourglass-shaped stenosis. (c-e) Sequential axial T2-weighted MR images reveal extensive compression of the popliteal artery by CAD (arrow).
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Figure 14c. A 42-year-old male runner presented with acute claudication of the left lower extremity and was initially thought to have popliteal entrapment. (a, b) Stress (a) and nonstress (b) angiograms depict a similar hourglass-shaped stenosis. (c-e) Sequential axial T2-weighted MR images reveal extensive compression of the popliteal artery by CAD (arrow).
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Figure 14d. A 42-year-old male runner presented with acute claudication of the left lower extremity and was initially thought to have popliteal entrapment. (a, b) Stress (a) and nonstress (b) angiograms depict a similar hourglass-shaped stenosis. (c-e) Sequential axial T2-weighted MR images reveal extensive compression of the popliteal artery by CAD (arrow).
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Figure 14e. A 42-year-old male runner presented with acute claudication of the left lower extremity and was initially thought to have popliteal entrapment. (a, b) Stress (a) and nonstress (b) angiograms depict a similar hourglass-shaped stenosis. (c-e) Sequential axial T2-weighted MR images reveal extensive compression of the popliteal artery by CAD (arrow).
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Because CAD is a rare condition, treatment methods are derived anecdotally. Cyst aspiration has been described (36), but cysts may recur. Balloon angioplasty (37) does not appear to be beneficial because it will not affect the cystic compression of the artery. Surgical evacuation of the cysts with maintenance of the native artery appears to be the preferred treatment. Occasionally, the artery cannot be preserved and a vein graft is required. Although not reported, in the rare case in which thrombosis of the popliteal artery has occurred, thrombolytic therapy would be appropriate prior to surgical correction, which would likely include bypass surgery.
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Conclusions
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The popliteal artery can be affected by a variety of pathologic conditions, the most common of which is atherosclerosis. Affected patients are usually older, presenting with other risk factors for atherosclerosis, less acute symptoms, and disease at multiple levels. PAA and embolus also manifest in these patients, but symptoms will be more acute with occlusion of the popliteal artery. When aneurysm of the aorta or of the iliac, femoral, or popliteal artery is diagnosed in one location, appropriate imaging should be performed to find associated aneurysms. In younger patients and in those without generalized atherosclerosis, the differential diagnosis includes trauma, CAD, and PAES. A high degree of suspicion may be necessary to make these relatively rare diagnoses. Color duplex US with segmental arterial pressure readings or an ABI can help localize and determine the extent of popliteal artery disease. MR imaging and MR angiography are important imaging tools, especially in CAD and PAES. Angiography is usually performed prior to surgical treatment and in conjunction with interventional therapies such as angioplasty and thrombolytic therapy.
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Footnotes
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Abbreviations: AAA = abdominal aortic aneurysm,
CAD = cystic adventitial disease,
PAA = popliteal artery aneurysm,
PAES = popliteal artery entrapment syndrome,
PTA = percutaneous transluminal angioplasty,
STAR = SCVIR Transluminal Arterial Revascularization
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References
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- Rutherford RB, Baker JD, Ernst C, et al. Recommended standards for reports dealing with lower extremity ischemia: revised version. J Vasc Surg 1997; 26:517-538.[CrossRef][Medline]
- Wang Y, Lee HM, Khilnani NM, et al. Bolus-chase MR digital subtraction angiography in the lower extremity. Radiology 1998; 207:263-269.[Abstract/Free Full Text]
- Morasch MD, Collins J, Pereles FS, et al. Lower extremity stepping table magnetic resonance angiography with multilevel contrast timing and segmented contrast infusion. J Vasc Surg 2003; 37:62-71.[CrossRef][Medline]
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Abstract
LEARNING OBJECTIVES
