Introduction
The criteria for defining arterial aneurysms as ‘a permanent localized dilatation of an artery having at least a 50% increase in diameter compared with the expected normal diameter of the artery in question’ was established by the Ad Hoc Committee on Reporting Standards of the Society for Vascular Surgery in 1991(1). Aneurysmal dilatation of an artery results from the structural weakening of the arterial wall, primarily due to factors such as atherosclerosis, trauma, infection or post-stenotic abnormalities. Peripheral arterial aneurysms (PrAAs) exclude the aorta, iliac, cerebral and coronary arteries (2).
True aneurysms involve all three layers of the normal arterial wall and are the most common type. By contrast, pseudoaneurysms, commonly referred to as false aneurysms, are enveloped by a thin fibrous capsule in place of the typical arterial wall layers (3-5).
Popliteal artery aneurysms (PAAs) are relatively uncommon, with an incidence of <0.1% in the general population; however, they account for >70% of PrAAs (6). These aneurysms predominantly affect men and typically occur around the age of 65 years; ~50% of the cases are bilateral and are often associated with abdominal aortic aneurysms (AAAs). Notably, >50% of patients present with symptoms, the most common being acute limb ischemia caused by thromboembolic complications, which are linked to elevated rates of morbidity and limb loss (5,6).
Within a 5-year period, ~68-74% of patients with untreated PAAs experienced complications. These primarily included distal embolization, thrombosis and rupture. Notably, thromboembolic complications were associated with a marked risk of major amputation (20-59%) and mortality (up to 11%) (7). By contrast, elective repair had a certain risk (~10%) for long-term limb loss in patients with low surgical risk. Thus, for PAAs reaching a diameter of 2 cm, elective surgical intervention is generally recommended (8).
Femoral artery aneurysms (FAAs) are the second most common type of PrAA, following PAAs. However, common FAAs (CFAAs) are relatively uncommon, while isolated superficial FAAs (SFAAs) and profunda femoris artery aneurysms are even rarer (9). Infra-PAAs (aneurysms of all arteries distal to the popliteal artery, including posterior tibial, anterior tibial and peroneal arteries) are a rare occurrence, primarily stemming from traumatic causes, with the majority being false aneurysms (10).
Upper limb aneurysms are an uncommon occurrence, constituting ~1% of all cases of PrAAs. Mostly they are subclavian-axillary artery aneurysms, which manifest at the outer border of the first rib, and the 3rd part of the axillary artery. These aneurysms, which are primarily post-stenotic in nature from thoracic outlet syndrome, are induced by factors such as the cervical rib or fibrous band (11).
Recently, endovascular treatment options have been employed to manage PrAAs, yielding diverse outcomes. Currently, the use of endovascular treatment for peripheral aneurysms should be reserved for specific cases involving high-risk patients. Until the development of devices that can counteract issues such as thrombosis and possibility of migration, as this part of the artery is highly mobile a tent in this position may end by extrinsic compression due to acute knee joint flexion. Traditional open surgery will remain the preferred treatment option (7,8,12). Open surgical treatment options include in-situ arterial replacement or a bypass with an autologous or prosthetic graft. To reduce the risk of late recurrence of the aneurysm, endoaneurysmorrhaphy is preferred compared with simple ligation of the artery proximal and distal to the aneurysm. Thrombolysis has also been used to improve outflow in patients with acute presentations (6).
The primary aim of the present study was to investigate the true PrAAs in a cohort of 30 selected patients who underwent open surgical repair. The present study identified and analyzed the risk factors associated with the development of PrAAs, assessing the impact of comorbidities on the treatment outcomes of patients with PrAAs. In addition, the study analyzed the long- and short-term outcomes of surgical repair for true PrAAs in the studied patient group.
Discussion
The present study aimed to examine the existing evidence concerning the natural progression and treatment of PrAAs and, more precisely, PAAs. It also aimed to apply decision theory techniques to establish the circumstances in which conservative management would be considered suitable. The present study confirmed the effectiveness of open surgical repair, which aligns with findings from previous studies that reported similar patency rates and minimal complications (12,14-16).
In the present study, PrAA rupture was not observed, and the most frequent primary complication observed was thromboembolism leading to acute limb ischemia. Notably, patients with PAAs exhibited an increase in local pressure on the popliteal vein, thus increasing the risk of popliteal vein thrombosis. This risk factor was associated with aneurysm size, with both PAA cases in this study measuring 3.6x3.2 cm. In addition, both patients in Group 2 presented with chronic limb ischemia, including major tissue loss. Furthermore, ~6.7% of the patients had experienced DVT, either during the study or preceding it. These findings are partially comparable with a number of other studies (12-14).
For asymptomatic patients and patients with mild-to-moderate claudication, the indication for intervention is less clear. Other factors that influence surgical decision-making are the development of symptoms, aneurysm size, mural thrombi, evidence of previous thromboembolism and anatomical risks of surgical repair (15,17).
The findings of Huang et al (17) suggested that thromboembolism may be the predominant complication in cases of PAA, while rupture remains rare. This previous study emphasized that the heightened risk of popliteal vein thrombosis was due to local compression, with 6% of the participants in the study having a history of current or previous DVT. Michaels and Galland (18) used Markov decision analysis to determine the ideal management of PAAs. This previous study indicated that conversative management could be used for asymptomatic patients, as the rate of aneurysmal enlargement was <10% per year and they were less likely to suffer adverse events.
A retrospective analysis (19,20) of popliteal aneurysms suggested that small aneurysms (≤2 cm) may not be as benign as previously considered. Despite their small size, these aneurysms may be lined with thrombi that can embolize the infra-popliteal arteries. Notably, 64% of the small aneurysms in these two series were partially thrombosed, which was not significantly different from the incidence of thrombosis in larger aneurysms (70%). In addition, complete thrombosis of the popliteal aneurysm was not associated with aneurysm size in the present series. Similar findings were obtained in the case series of the present study.
A review of 12 publications revealed that the development of symptoms was at an average of 14% per year (range, 5-24%) (18). In a study conducted by Lowell et al (20), asymptomatic patients with PAAs were monitored without surgical intervention, with an average follow-up duration of 17 months. During this timeframe, 18% of the patients exhibited symptoms. Risk factors associated with the development of symptoms included aneurysm size exceeding 2 cm, poor runoff and the presence of a mural thrombus (P<0.05).
Treatment for PAAs has become more aggressive to prevent limb loss. The current literature on PAAs has been limited primarily to surgical series, with a minor description of patients treated conservatively (21,22). Following PAAs, FAAs represent the most prevalent PrAAs. These aneurysms can occur bilaterally and are commonly associated with additional arterial aneurysms, particularly those in the aortic region. It is recommended that symptomatic FAAs larger than 3 cm undergo treatment (23). In the upper extremities, aneurysmal development at the level of the brachial and radial arteries is most commonly secondary to trauma, invasive interventions and atrioventricular fistulae for hemodialysis. True aneurysms of the subclavian artery are uncommon, accounting for only 0.1% of all PrAAs. In addition, post-stenotic dilatation or atherosclerotic degeneration serve a role in their etiology (24-26).
In the present study, the size of PrAAs measured by duplex scan (3.4±1.06 cm) emerged as a critical risk factor for thrombus formation. The significance of thrombus formation size indicated that even small aneurysms pose a heightened risk of thrombus development, leading to limb ischemia and the potential for amputation. Consequently, in the present study, even asymptomatic patients underwent surgical repair as a preventive measure to avert limb loss. Notably, no notable difference was detected in the diameter of PrAAs when assessed using duplex ultrasound and CTA, both yielding a mean measurement of 3.4±1.06355 cm. Consequently, neither method demonstrated superiority in size measurement.
Others have also reported a heightened incidence of complications in this particular group (patients with acute limb ischemia) (27,28). However, it is worth noting that one publication covering 51 patients, including 14 who underwent emergency repair, indicated no instances of early mortality or cardiac complications (28,29). In the series of the present study, acute ischemia was associated with an 8% risk of early limb loss and a 15% risk of late limb loss.
In another study, the preferred graft was a GSV, which was implanted through a medial approach. The GSV is advantageous due to the ease of vein harvesting and convenient access to the anastomotic sites to ensure optimal inflow and outflow. In two thirds of the cases, the femoral artery served as the location for the proximal anastomosis, while the infra-popliteal artery was utilized distally in a quarter of the operations (30-32). The potential benefits of employing tibial arteries for distal anastomosis as needed have been underscored by a number of authors. For all but small, thrombosed aneurysms, endoaneurysmorrhaphy should be performed to prevent late recurrence, and this recommendation extends to other PrAAs (33-35).
In our center, endoaneurysmorrhaphy was performed for all patients. Re-intervention was observed in only two cases. This approach demonstrated a notably high patency rate when compared with alternative techniques observed in other studies. Surgical intervention for upper-extremity aneurysms should be initiated without delay. Risk factors combined with the minimal morbidity associated with repair suggest that surgical repair should be performed routinely for true upper extremity arterial aneurysms (36,37).
In the present study, the follow-up for graft patency was 2 years. All 6 patients with PTFE grafts had 100% patency. In those with GSV grafts, primary patency was 90.47% and secondary patency was 95.23%, which was significantly higher for GSV compared with Dacron grafts. Dacron graft primary patency was 33.33% and secondary patency was 66.66%. The standard approach for interposition grafting typically involves using a prosthetic graft, with PTFE being the most commonly utilized material. The choice of graft material has become a topic of some debate. This is because a prosthetic graft, especially PTFE, is well suited in size to the enlarged popliteal artery (32,36).
Additionally, a considerable number of patients with PAAs exhibit good-to-excellent runoff, ensuring high flow and prolonged patency of a prosthesis (17). In a study by Pulli et al (29), no significant difference in patency at 60 months was observed between 118 PTFE grafts (71.5%) and 34 vein grafts (79.9%). However, it is worth noting that the number of limbs at risk during this time interval was not reported.
The present study is limited by its interpretations being drawn from a single center only and further by its retrospective analysis; however, the data were collected prospectively. The limitations of the present study include the single-center design and a relatively small sample size, which may introduce bias. Additionally, the follow-up period of a minimum of 18 months might not capture long-term outcomes or complications. Longer follow-up durations would provide more comprehensive insights into the durability of the interventions and the occurrence of late complications or recurrences.
Although general management guidelines as outlined in the present study report were followed, the selection of graft material, surgical technique, and indications for elective surgery were at the discretion of the operating vascular surgeon. No randomization was performed to evaluate different techniques. The present study supports the efficacy of open surgical repair, particularly endoaneurysmorrhaphy, in achieving high primary and secondary patency rates, and low rates of limb loss and mortality. These findings suggest that open repair should remain a preferred treatment option for PrAAs. Despite the challenges posed by acute limb ischemia and systemic complications, early intervention and meticulous follow-up contribute to reducing adverse events.
Moving forward, future research should focus on the risk factors and pathophysiological mechanisms underlying PrAA development, and evaluate the comparative effectiveness of endovascular and open surgical approaches in larger, multi-center studies. Future research should focus on identifying specific risk factors and pathophysiological mechanisms underlying PrAA development, as well as comparing the long-term outcomes of endovascular vs. open surgical approaches in a larger, multi-center cohort.