Aneurysms of the Peripheral Arteries

Incidence and Cause

A common femoral artery (CFA) aneurysm is defined as a localized dilatation of 1.5 times the expected size of a normal adjacent segment of artery. According to the reporting standards for the Society for Vascular Surgery, the normal diameter of the CFA is 0.78 to 1.12 in men and 0.78 to 0.85 in women. Cutler and Darling classified CFA aneurysms into two categories: type 1 which involved the CFA up to the femoral bifurcation; and type 2 which extended into the profunda femoris. Type 1 represent the majority, with 44% to 85%. CFA aneurysms are the most common, but occasionally these aneurysms are located only in the deep or superficial femoral artery.

Dent and colleagues showed an association between femoral and popliteal aneurysms and other aneurysms of atherosclerotic origin. Most commonly, these associated aneurysms are located in aorta-iliac vessels, but more rarely can involve the renal, splanchnic, and brachiocephalic vessels. Among patients with at least one peripheral aneurysm, 83% had multiple aneurysms. Among patients with a common femoral aneurysm, 95% had a second aneurysm, 92% had an aorta-iliac aneurysm, and 59% had bilateral femoral aneurysms.

Natural History

The natural history of femoral aneurysms, like popliteal aneurysms, is associated with a significant incidence of thromboembolic events. Hall and colleagues reported that approximately 30% to 40% of patients with CFA aneurysms are asymptomatic at initial presentation, while anywhere from 10% to 65% present with ischemic complications due to either thrombosis or distal embolization. Symptoms can vary from claudication to critical limb ischemia. Tolstedt and associates reported a 43% rate of thrombosis in conservatively managed femoral aneurysms, and in Cutler and Darling's series, 47% exhibited major complications. Rupture of femoral aneurysms is rare. Deep femoral aneurysms, however, are thought to be particularly prone to rupture, with reported rates of 13% to 45%. While the incidence of deep femoral aneurysms is much lower, more than half will present with complications and greater than 80% will have associated aneurysms in other vascular beds.

Diagnosis

Diagnosis is most often made by palpation because of the femoral artery's relatively superficial location. Femoral aneurysms should be considered in any patient with an acute lower extremity arterial occlusion or with evidence of embolic disease affecting the foot and leg. Femoral aneurysms are easily diagnosed by ultrasonography and some authors have suggested the routine use of ultrasonography to look for femoral and popliteal aneurysms in men with aortic aneurysms. Computed tomography angiography (CTA) is particularly accurate in making the diagnosis and is helpful in planning open and endovascular repair ( Fig. 47.1 ). Arteriography is usually not required when a high-quality CTA is available.

Indications for Aneurysm Repair

Conventional recommendations for the treatment of femoral aneurysms include all symptomatic aneurysms of any size, aneurysms with intramural thrombus, aneurysms greater than 2.5 cm, aneurysms that show growth with surveillance, and those that change their baseline pulse exam, indicating embolization. This recommendation is based on the high incidence of thromboembolic complications associated with these lesions, as detailed earlier, and the low morbidity and mortality associated with repair.

A more recent study by Lawrence and the Vascular Low-Frequency Disease Consortium has brought into question the current recommendations for repair based on a size of 2.5 cm. In their multivariate analysis they found that size 4 cm or greater and intraluminal thrombus were indications for repair and significantly associated with complications in patients managed nonoperatively ( P = .001), as was age less than 60 years ( P = .004). Location of the femoral aneurysm (common, profunda, superficial) was not significantly associated with complications. This analysis indicates that the current recommendation of greater than 2.5 cm as an indication for repair of asymptomatic common femoral, superficial femoral, and profunda aneurysms without thrombus may be too liberal and should be changed to 3.5 cm or more. One caveat to this recommendation is that the presence of thrombus was a predictor of symptomatic progression and an indication for repair at a smaller size.

Treatment

The treatment of degenerative femoral artery aneurysms is usually resection and graft interposition ( Fig. 47.2 ). Because of the size of the CFA, a prosthetic graft is preferred. When the deep femoral artery is involved, the graft may be sewn end to end to the superficial femoral artery, and the origin of the deep femoral artery implanted into the side of the graft. When femoral aneurysms are being treated concomitantly with an inflow or outflow procedure, it is preferable to replace the CFA with an interposition graft with inflow or outflow grafts anastomosed to the interposition graft in an end-to-side fashion. Releasing the inferior border of the inguinal ligament, dividing the inguinal ligament, or making a separate retroperitoneal incision can assist in gaining proximal control of the external iliac artery. Additionally, proximal endovascular balloon control from a contralateral femoral access can help in selected cases. Stent-grafting for common femoral aneurysms is rarely if ever indicated. Stents and stent-grafts in the CFA are subjected to significant flexion forces as a result of hip flexion, and there is concern regarding stent fracture and compression. In addition, stents and stent-grafts in this area may complicate future arterial access. Furthermore, coverage of the profunda femoris orifice by the stent-graft excludes a critical thigh vessel from antegrade flow.

Repair of a deep femoral artery aneurysm is dictated by the patency of the superficial femoral artery and the distal extent of the aneurysm. Although, approximately 50% of deep femoral aneurysms can be safely ligated, in-line repair should be performed when technically feasible. Exposure for the profunda femoris artery requires reflecting the sartorius and rectus femoris muscles laterally. Division of deep femoral vein branches is often required, and associated femoral nerve branches should be identified and protected. Repair can be accomplished with an interposition graft of saphenous vein, but prosthetic grafts are also acceptable in the absence of vein conduit.

Usually, superficial femoral artery aneurysms are an extension of a popliteal aneurysm. Treatment of isolated superficial femoral artery aneurysms can be performed by either open surgical repair or endovascular techniques. Open repair can be accomplished by either aneurysm resection and interposition grafting or aneurysm ligation and bypass. Stent-grafting can be applied anywhere along the superficial femoral artery as long as there are adequate landing zones. As with popliteal artery aneurysms, superficial femoral artery aneurysms treated with ligation or a stent-graft may be subject to enlargement secondary to type II branch endoleaks.

Outcomes

When femoral aneurysms are treated before complications arise, the results are excellent. The 18 asymptomatic patients with femoral aneurysms in the series by Cutler and Darling all had excellent early and late results (no graft occlusions). However, of the 45 symptomatic patients with femoral aneurysms, 4 had amputations, and 17 remained symptomatic despite therapy.

Harbuzariu and colleagues followed 17 patients with profunda femoris aneurysms, 11 of which were asymptomatic. Fifteen of the profunda femoris aneurysms were treated with bypass grafting. There was no 30-day death, graft thrombosis, or limb loss. Long-term graft patency was 100%.

As mentioned previously, Lawrence and colleagues collected a series of 236 femoral artery aneurysms (191 CFA, 11 PFA, 34 SFA) in 182 patients. One hundred fourteen patients were initially managed nonoperatively, and 64% of these patients later required repair. Of these patients, the most common indication for repair was development of intraluminal thrombus, followed by increase in diameter to greater than 2.5. In addition, acute complications occurred in 12 and rapid enlargement in 7. Of the patients treated surgically, 98% were treated with open repair, 80% interposition graft, and 20% bypass. Major postoperative complications occurred in 20%. Five-year survival was 61%, and none of the patients developed critical limb ischemia or required amputation during the follow-up period (range 1 to 93 months), providing a 100% limb salvage rate at 5 years.

Incidence and Cause

Aside from trauma and rare degenerative and congenital disorders, popliteal aneurysms are almost exclusively atherosclerotic in origin. These aneurysms account for about 70% of peripheral aneurysms, occurring in about 1% of men aged 65 to 80 years old, with a 20-to-1 male-to-female ratio.

Among patients with a popliteal aneurysm, 78% have a second aneurysm, 64% have an aorta-iliac aneurysm, and 47% have bilateral popliteal artery aneurysms. In a recent study, the incidence of femoral and popliteal aneurysms in men with a known abdominal aortic aneurysm was 14% (0% in women). Of importance is that most of the femoral and popliteal artery aneurysms were undetectable by physical examination, emphasizing the need for ultrasound screening for femoral and popliteal aneurysms in men with an abdominal aortic aneurysm. Patients with peripheral aneurysms are also at high risk for the development of future peripheral aneurysms. Dawson showed that in patients with a popliteal artery aneurysm, new peripheral aneurysms were detected in 32% of these patients after 5 years and in 49% of these patients after 10 years.

Natural History

The natural history of popliteal aneurysms is associated with a high incidence of thromboembolic events, both acute and chronic. Szilagyi and colleagues reported that only 32% of patients with popliteal aneurysms managed conservatively remained without complications at 5 years. Dawson and colleagues compared operative and nonoperative approaches in 50 patients with 71 popliteal artery aneurysms. Thromboembolic complications developed in 57% of patients over a mean follow-up period of 5 years. In patients followed for a full 5 years, the complication rate was 74%. Up to three-quarters of patients with popliteal aneurysms present with symptoms, including claudication, chronic embolization with ischemia, acute limb ischemia from embolism or thrombosis, or swelling and pain from aneurysm expansion and compression. Rupture of a popliteal aneurysm is rare. Rupture can occur into the popliteal vein and is associated with a high rate of limb loss. Less catastrophic complications include pain secondary to tibial nerve compression and popliteal vein thrombosis secondary to popliteal vein compression.

Diagnosis

A popliteal aneurysm should be suspected in any patient in whom the popliteal pulse is widened and easily palpated, in any patient with an acutely ischemic limb despite a femoral pulse, or in any patient with evidence of distal embolic occlusion of the infrapopliteal arterial tree. Many popliteal aneurysms are calcified on plain radiographs of the popliteal fossa. The diagnosis of a popliteal aneurysm is most expeditiously made by ultrasonography. CTA is particularly helpful in confirming the diagnosis and planning open or endovascular treatment ( Fig. 47.3 ). Arteriography is currently rarely necessary for elective operative repairs, but is essential for patients with acute thrombosis and limb threatening ischemia. The status of the infra-popliteal arterial tree demonstrated on either CTA or arteriography is particularly important, since the patency of runoff vessels directly correlates with early and late graft patency for both open and endovascular approaches ( Fig. 47.4A to D ).

Indications for Aneurysm Repair

Current recommendations for repair of popliteal aneurysms include aneurysm size 1.5 to 2.0 cm with thrombus, all aneurysms of 2 cm or greater in size, all symptomatic aneurysms, and those with evidence of occult distal embolization. This recommendation is based on the high incidence of thromboembolic complications associated with these lesions, as detailed earlier, and the low morbidity and mortality associated with repair. The indications for revascularization in the patient with a chronically thrombosed popliteal aneurysm are the same as those used for patients with peripheral arterial occlusive disease.

Treatment

Repair of a popliteal artery aneurysm can be accomplished by either open or endovascular repair. Which approach is used depends on a number of factors including patient comorbidities, runoff vessel patency, popliteal artery tortuosity and length of vessel involvement.

Open repair of popliteal artery aneurysms was first accomplished by aneurysm ligation with above-knee to below-knee bypass through a medial approach. More contemporary series have described a posterior approach with aneurysm resection and interposition graft replacement. Since both approaches are effective, which one is employed for a given patient is dependent on surgeon experience, aneurysm size, and proximal and distal extent of the aneurysm. Extension of aneurysmal degeneration into the superficial femoral artery or infra-geniculate arterial tree precludes a posterior open approach. In this anatomic situation, the proximal and/or distal anastomoses of the arterial reconstruction are best approached medially. When popliteal aneurysms are large enough to cause symptomatic compression of the surrounding tibial nerve and popliteal vein, resection of the aneurysm with interposition grafting through a posterior approach is preferred, as long as the aneurysm extent does not preclude a posterior approach. The posterior approach has the benefit of complete aneurysm decompression, which does not always occur with medial ligation and bypass. There have been reports of higher rates of nerve damage from a posterior approach, particularly with large extensive aneurysms; however, a recent meta-analysis found no statistically significant difference between the two approaches with respect to nerve damage.

Results of surgery are generally better when autogenous vein is used for surgical repair, when compared to polytetrafluoroethylene (PTFE) grafts, with superior patency in long-term follow-up. PTFE, when used, provides reasonable results for focal aneurysms with good vessel runoff. When chronic embolization leads to obliteration of the outflow tract of the popliteal artery, bypass to the tibial or peroneal arteries is required, and these bypasses should always be performed using autogenous vein.

When patients develop acute thromboembolic complications of popliteal artery aneurysms, the degree of arterial occlusion is often so great that no outflow vessel is visualized by CTA or arteriography. Many of these patients also have thrombosis of the microcirculation. In such patients, bypass is often not possible or is subject to a high failure rate, due to poor runoff. In this situation, the use of pre-repair thrombolytic therapy can frequently establish patent runoff and improve the microcirculation, thereby allowing for successful bypass or stent-grafting. Following acute thrombosis of a popliteal artery, graft patency and limb salvage rates after initial thrombolysis have been reported to be superior to early operative intervention alone.

Endovascular stent-graft repair of a popliteal artery aneurysm was first reported in 1994 by Marin and colleagues. Since then, numerous reports have been published on the use of stent-grafts in this arterial location. These studies report shorter operative time and hospital stay and less perioperative morbidity. For endovascular stent-graft repair, it is clear that patients with two to three vessel runoff and proximal and distal landing zones, ideally 2 cm, but at a minimum 1.5 cm, are the best candidates. Stent-grafts have also been used successfully in the treatment of ruptured popliteal aneurysms. Relative contraindications to endovascular repair of popliteal artery aneurysms include extension of aneurysmal disease to the superficial femoral artery proximally or distally into the anterior tibial, tibioperoneal trunk origin, as well as tortuosity, single vessel runoff, and large aneurysms with compression symptoms.

Outcomes

Open repair of popliteal aneurysms has been extensively studied; outcomes are influenced by acuity, symptom status, and runoff vessel patency. In a study of 48 popliteal aneurysms, the 5-year patency for reconstructions of asymptomatic lesions was 91%, compared with 54% for symptomatic lesions, and results were directly related to the status of the tibial runoff vessels. In a series of 51 popliteal aneurysms reported by Shortell and colleagues, results were dependent on the clinical presentation and the status of the runoff vessels. Patients with limb-threatening ischemia had a graft patency of 69% at 1 year, whereas all electively performed grafts in asymptomatic patients were patent at 1 year. After 3 years, runoff dictated patency; grafts with good runoff had a patency rate of 89%, whereas poor runoff was associated with a 3-year patency rate of only 30%. Numerous, more recent reports of large series of popliteal aneurysms have confirmed these earlier results. Huang and colleagues reported on 358 popliteal aneurysms treated with open surgical approaches. Forty percent were asymptomatic, 39% had chronic ischemia, and 21% had acute ischemia. The 30-day thrombosis rate was 1% in asymptomatic limbs, 4% in limbs with chronic ischemia, and 9% in limbs with acute ischemia. There were three deaths and six early amputations, all in the acute ischemia group. Five-year primary and secondary patency rates were 76% and 87%, respectively, with saphenous vein patency being significantly higher than PTFE patency (94% vs. 85%). The 5-year limb salvage rate was 97%, but only 85% in the acute ischemia group. Within that group, limbs treated with preoperative thrombolysis had better limb salvage (96%) than those limbs treated with surgery alone (69%). Two percent of aneurysms required reintervention for aneurysm enlargement, and all these limbs had been treated with ligation and bypass. In 2015, a retrospective review of 234 open popliteal artery aneurysm repairs in 196 patients evaluated long-term patency. This study found primary patency rates of 65.5%, 58%, and 55% at 5 years, 10 years, and 13 years, respectively. Secondary patency rates were reported to be 75.7% at 5 years, 69.5% at 10 years, and 68% at 13 years.

Since Edwards first described the technique of bypass with aneurysm ligation through a medial approach, it has been the preferred open method of repair. In the vast majority of surgical series described above, the Edwards technique was used. However, as experience has accumulated, it became evident that late aneurysm expansion and even rupture can occur. In 2003, Ebaugh and colleagues reported the Northwestern experience with 57 popliteal aneurysms treated with aneurysm ligation and bypass. At a mean follow-up of 4.3 years, 32% of aneurysms treated in this manner had expanded. The authors hypothesized that type II endoleaks were the cause, but neither graft patency nor contrast filling of the aneurysms on contrast CT scans could be found to correlate with aneurysm expansion. Bellosta and colleagues also assessed late aneurysm expansion after the ligation–bypass technique and found an 8% incidence of postoperative aneurysm expansion in 53 aneurysms followed for a mean of 35 months.

Beseth and Moore reported on 30 popliteal aneurysms that were treated through a posterior approach using a short prosthetic interposition graft repair. Mean follow-up was 21.5 months. Primary patency, primary assisted patency, and secondary patency were 92.2%, 95.8%, and 95.8% at 1 and 2 years. Limb salvage was 100%. Aneurysms that extended proximal to the adductor canal were excluded from the posterior approach, and all aneurysms had one or more patent tibial artery runoff vessels. The authors noted that their results were comparable to the exclusion–bypass technique, but had the added advantage of allowing aneurysm resection or aneurysmorrhaphy with oversewing of popliteal perigeniculate branches with the elimination of risk for postoperative aneurysm expansion. Ravn and colleagues analyzed the Swedish Vascular Registry which contained 717 popliteal aneurysms. Mean follow-up was 7.2 years. The medial approach was used in 87%, the posterior approach in 8.4%, and an endovascular approach in 3.6%. There was no difference in patency between vein and prosthetic graft when the posterior approach was used, but there was better patency with vein using the medial approach (90% vs. 72%). Emergency procedures and the use of prosthetic graft were associated with higher amputation rates. Postoperative aneurysm expansion was demonstrated in 33% when the medial approach was used, but in only 8.3% when the posterior approach was used. Zaraca and colleagues found that the posterior approach was possible in 78% of aneurysms using proximal extension above the adductor canal as the primary contraindication to posterior repair.

A 2016 meta-analysis by Phair and colleagues compared the posterior and medial approach for open repair. Primary outcomes were major perioperative complications, primary patency, secondary patency, and limb loss. A total of seven studies from 2007 to 2015 with a total of 1427 patients were evaluated. There were 338 that underwent a posterior approach and 1089 that underwent a medial approach. Use of preoperative or perioperative thrombolysis was not consistently reported. There was no statistical difference in nerve damage, 30-day complications, 30-day limb loss, or 30-day primary patency. When looking at 30-day secondary patency, results suggested superiority of the posterior approach (risk difference [RD], 0.05; 95% confidence interval [CI], 0.02 to 0.07; P = .002). Follow-up ranged from 46 to 96 months (217 posterior, 740 medial) with long-term primary patency favoring the posterior approach (odds ratio [OR], 1.61; 95% CI, 1.06 to 2.43; P = .02). Successful aneurysm exclusion (138 and 107 posterior and medial approaches, respectively) and reoperation (122 posterior and 683 medial) confirmed posterior approach superiority with OR 4.2 (95% CI, 1.4 to 12.6; P = .01) and OR 0.26 (95% CI, 0.09 to 0.72; P = .01), respectively. Limb loss at the study end point was not significantly different between the two groups. Based on these findings they concluded that the posterior approach should be considered as the preferred approach for popliteal artery aneurysm (PAA) not extending above the adductor hiatus.

Because of the inferior results of endovascular or open repair once acute thromboembolic complications have occurred, attention has focused on the reestablishment of runoff preoperatively through the use of thrombolytic therapy. Most reports indicate good success in improving runoff and suggest improved limb salvage when preoperative thrombolytic therapy is used. Varga and coworkers performed a retrospective, multicenter study of 200 popliteal aneurysms and concluded that intra-arterial thrombolytic therapy clearly improves preoperative runoff in patients with acute limb-threatening ischemia. Hoelting and associates described 24 patients with acute ischemia secondary to popliteal artery aneurysm thrombosis. Nine patients were treated with preoperative thrombolysis and underwent successful bypass. Six of these patients achieved complete lysis. For three patients, lysis was incomplete but established sufficient runoff so that successful bypass could be performed. These authors also reviewed the literature and reported an amputation rate of approximately 27% in 455 patients treated with bypass alone, compared with approximately 20% in 14 patients in whom only thrombolytic therapy was used. In 30 patients in whom thrombolytic therapy was combined with bypass, no limb was lost. Varga and colleagues suggested that thrombolysis is of value in restoring distal runoff before bypass in the presence of limb-threatening ischemia. Carpenter reported on seven limbs with popliteal aneurysm thrombosis and complete thrombosis of all runoff vessels. These patients were treated with preoperative thrombolysis, with 100% limb salvage and superior graft patency compared to similar patients not treated with preoperative thrombolysis.

Early experience of popliteal artery aneurysms with stent-grafts demonstrated technical success, but patency was considerably lower than that achieved with aneurysm ligation and bypass. However, Tielliu in 2005 reported on 57 popliteal aneurysms treated (five emergently) with stent-grafting. Primary and secondary patency rates were 80% and 90% at 1 year and 77% and 87% at 2 years; use of postoperative clopidogrel was predictive of success.

More recent analyses comparing open and endovascular repair have demonstrated inferior patency with endovascular repair in the early postoperative period. In a review of the Vascular Quality Initiative from 2015, open repair demonstrated superior 1 year primary patency, with hazard ratio (HR) of 0.25 (95% CI, 0.10 to 0.58). A similar review of a prospectively collected database in Sweden with 592 repairs reported inferior primary and secondary patency at 1 year with endovascular repair. This difference was most pronounced in patients presenting with acute limb ischemia with primary and secondary patency for endovascular repair being 42% and 48%, respectively, compared to 78% and 87% for open repair. With regard to patients with asymptomatic aneurysms, there was a significantly better primary patency and secondary patency at 1 year ( P < .001; P = .026) following open repair.

Golchehr and colleagues reported their experience with a placement of heparin bonded ePTFE stent-grafts in a smaller cohort of patients with follow-up over a 5-year period. Published in 2016, they retrospectively reviewed a prospectively collected database and identified a total of 72 aneurysms treated in 70 patients. All patients had aneurysms greater than 2 cm, with two or more outflow vessels, and greater than 1.5 cm proximal and distal landing zones. Patients with below knee popliteal arteries of less than 4 mm were excluded, and maximum oversizing of stent-grafts was 15%. All patients received dual antiplatelet therapy for 6 months, followed by single agent long-term. Of these patients, 78% were initially asymptomatic and only 9% had acute limb ischemia on presentation. There were no significant factors identified that were associated with loss of patency. Primary patency at 1, 2, and 3 years was 83%, 69%, and 69%, respectively. Secondary patency was 88%, 81%, and 76% at 1, 2, and 3 years, respectively, and there were no major amputations during the follow-up period of 0 to 63 months (median 13). The authors concluded that mid-term outcomes with stent-grafts were promising and this approach deserved consideration.

In 2015, the largest meta-analysis to date was published comparing endovascular to open repair. A total of 652 repairs were evaluated across five studies (236 endovascular, 416 open). Endovascular patients were significantly older (75 ± 6 years vs. 68 ± 3 years mean diff [MD], 6.95; 95% CI, 4.04 to 9.86; P < .001) and had fewer symptoms (OR, .38; 95% CI, 0.26 to 0.54; P < .001). No difference in emergency cases or poor vessel runoff was found. All patients were treated postoperatively with dual antiplatelet for at least 1 month, or oral anticoagulation plus one antiplatelet agent. Thirty-day graft occlusion rates (9% vs. 2%; OR, 3.16; 95% CI, 1.31 to 7.62; P = .01) and reintervention rates (9% vs. 4%; OR, 2.15; 95% CI, 1.02 to 4.55; P = .04) were significantly higher for endovascular repair. Length of procedure and length of hospital stay (3.5 vs. 7.3 days; P < .001) were significantly less for endovascular repair, consistent with nearly all studies comparing the two treatment modalities. There were no significant differences in survival, limb loss, and primary patency, and 4-year cumulative primary patency rates were 54% to 86% for endovascular versus 63% to 88% for open. They concluded that dual antiplatelet therapy appeared to assist with improved early patency rates as compared to earlier studies and reported that midterm patency rates are comparable to open repair.

These recent reports suggest that an endovascular approach to patients who have certain anatomic prerequisites is reasonable, particularly in elderly patients with comorbidities or in patients lacking autogenous vein. Anatomic prerequisites include 1.5 to 2 cm proximal and distal landing zones in the popliteal artery and at least two-vessel runoff. Dual antiplatelet therapy is also critical and required for a durable repair.

Incidence and Cause

Infrapopliteal, or tibial artery, aneurysms are uncommon, and true aneurysms are exceedingly rare. The majority of reported cases of aneurysms of the infrapopliteal arteries are secondary to trauma or infection. Data in the literature on true aneurysms consist of individual cases or small case series.

Natural History

Patients may be asymptomatic, complain of intermittent claudication, painful pulsatile mass, or neurologic symptoms from nerve compression. Alternatively, patients may present with acute or chronic critical limb ischemia from distal embolization or thrombosis of the aneurysm, or rarely of rupture.