The Angiosome Concept and Endovascular Techniques for Limb Salvage

Abstract

The aim of this chapter is to provide an overview of patients with arteriopathy, especially in the infrapatellar segment, which is the most affected in diabetic patients. In this sense, we always try to analyze the degree of disease of the patient and, if limb salvage intervention is necessary, to evaluate the new technologies that promote higher rates of technical success with less tissue aggression. In addition to the TASK classification, which provides an idea of the degree of obstruction and thus facilitates therapeutic decision-making, the use of various classifications has been demonstrated, which aims to promote better communication between physicians about the state of ischemia and the degree of injury. The different techniques used were presented, thanks to the development of new materials, with more and more possibilities for saving limbs.

1. Introduction

Peripheral obstructive arterial disease (PAD) classically has smoking, systemic arterial hypertension, and diabetes mellitus as major risk factors, with dyslipidemia as an adjuvant factor. The atherosclerotic disease can affect any part of the body, leading to myocardial infarction, stroke, bowel infarction, or distal amputation, depending on the area affected [1]. It is known that the patient with diabetes mellitus has as a major factor of morbidity and mortality, so-called diabetic foot, which can be neuropathic, ischemic, or infectious, usually with two or more of these associated factors. In these patients, it is very common to observe diffuse arterial occlusions at multiple levels, with a predominance of the territory below the knee (BTK), causing distal hypoperfusion and reducing limb viability, with a high risk of amputation [2].

Nearly 50% of patients with diabetes and foot ulcers have peripheral arterial disease (PAD). At the same time, in different stages of the disease with increased risk of adverse events in the limbs and cardiovascular disease, the management of these patients is different concerns in terms of diagnosis, prognosis, and treatment [3]. Critical limb ischemia is the result of many pathological aspects such as hypertension, diabetes mellitus, hyperlipemia, and renal failure. These conditions lead to an atherosclerotic obstructive disease with diffuse, multilevel, and multivessel calcifications, called Monckberg’s disease, which causes enormous technical difficulties in the revascularization of the lesions [4].

The angiosome model was pioneered by Jan Taylor in 1987 through his influential anatomical works in the field of plastic reconstructive surgery. The model portrays the human body in three-dimensional tissue blocks that are supplied by precise arterial and venous irrigation sources, referred to as “angiosomes” [5].

Depending on the underlying cause of the process that leads to arterial obstruction, there are different patterns of obstruction in the arterial tree, as well as the characteristics of the obstruction, which can include soft plaques, thrombi, fibrotic or calcified plaques, and of course, a mixture of these types of plaque. It is known that the mortality rate of diabetic patients after amputation is about five times higher than that of the general population. Amputation rates in the diabetic population are approximately 10–20 times higher than in the nondiabetic population. Of all amputations in diabetic patients, 85% are preceded by foot ulceration that progresses to gangrene or severe infection. It is estimated that a lower limb is amputated every 30 seconds because of diabetes. These ulcerated feet are usually compromised primarily by ischemia and neuropathy [6, 7, 8].

Thus, the methods of revascularization evolved, from a time when practically only amputations were indicated evolving to sympathectomies and the use of vasodilators and later via bypass until the appearance of endovascular methods, whose technical and material improvement allow for high rates of limb salvage today. The concept of angiosome has accompanied this evolution, and it is only possible to apply this concept in practice through excellent imaging tests, technical capacity of the surgical and multidisciplinary team, and high-quality materials and technology.

2. Epidemiology

In diabetic patients, PAD is one of the leading causes of amputation. Together with neuropathy and infection, it leads to high rates of limb loss. More than 85% of these amputations are caused by a foot ulcer that progresses to deep infection or gangrene. The prevalence of diabetic foot ulcers is estimated to be 3–8% [9]. The age-adjusted prevalence of diabetes has nearly doubled since 1980, from 4.7 to 8.5% of the adult population. Over the past decade, the prevalence of diabetes has increased rapidly in the poorest countries. Myotonic dystrophy type 2 (DM2) has historically been considered a disease in developed countries, but this epidemiologic pattern is changing, and developing countries are experiencing an increasing prevalence of DM2. Currently, the global prevalence of DM2 in people aged 18 years and older has increased from 4.7% in 1980 to 8.5% in 2014, and this increase is greater in developing countries [10]. Diabetes mellitus was once considered a disease that affected the elderly and people of good socioeconomic status, but it is now believed that more than 80% of diabetic deaths occur in developing countries. About 15% of people with diabetes will develop ulcers in their lifetime, and between 14 and 43% of those will require amputation. Considering the complexity of the illness, a multidisciplinary approach is necessary, which includes endocrinologists, general and vascular surgeons, interventional radiologists, neurologists, orthopedists, and specialized nursing teams. Nevertheless, limited access to some specialties and a lack of consensus on the subject hinder the formation of multidisciplinary teams [11]. Based on the 2015 data from the International Diabetes Federation, an estimated 9.1–26.1 million people worldwide develop diabetic foot ulcers each year. The number of adults with DM quadrupled from 1980 to 2014, mainly due to the increase in obesity and overweight, and the high number of people with diabetes has led to an increase in the incidence of diabetic foot ulcers and peripheral arterial occlusive disease (PAOD) [12]. The risk of death after 5 years is 2.5 times higher for patients with foot ulcers and diabetes than for patients with diabetes without ulcers [13].

3. Pathophysiology

Peripheral artery disease is usually caused by atherosclerosis. In patients with diabetes, we often observe early development of atherosclerotic lesions that are characteristic of poorly controlled and chronic diabetics. PAD is a significant risk factor for impaired wound healing and amputation of the lower extremities. It is imperative to note that foot ulcers often result from a combination of risk factors, therefore, proper examination by a healthcare professional is essential. A small proportion of foot ulcers materialize in patients with severe, purely ischemic PAD; these ulcers are frequently painful and can manifest themselves after minor injuries. Meanwhile, most foot ulcers occur in individuals with pure neuropathic feet who develop infections because of deformities and plantar insensitivity, as well as a combination of neuropathy and arteriopathy. Patients with neuroischemic ulcers may have no symptoms because of neuropathy despite severe ischemic foot disease. Features of peripheral arterial disease in diabetics are as follows:

• lesions with greater calcification of the physician

• worsening in distal collateral circulation

• rapid progression

• multisegmental lesions

• increased risk of amputation

In addition, the presence of moderate or severe infectious conditions greatly increases the likelihood of amputation by placing greater metabolic demands on tissues where the lack of blood supply is easily overwhelmed by the demand, leading to necrosis.

PAD increases the risk of ulcers, infections, and unhealed amputations independently. Mortality rates in patients with diabetes exceed 70% after diabetes-related amputations at 5 years and 74% at 2 years for those on renal replacement therapy [11].

Arterial disease in diabetic foot syndrome (DFS) has specific characteristics that have led to the development of the concept of diabetic distal arterial disease. These concept group’s micro- and macroangiopathic changes such as non-occlusive lesions of the microcirculation (resulting from endothelial dysfunction caused by hyperglycemia and hyperinsulinemia), aggressive atherosclerotic changes with multilevel arterial blockages (involving medium and large caliber arteries), reduced collateral circulation, inflammation, and local sepsis with acute septic thrombosis [14].

4. Diagnosis and clinical examination

When confronted with a patient with diabetes mellitus, in addition to a comprehensive laboratory analysis aimed at establishing the degree of metabolic dysfunction, one should observe aspects that may alert about the prognosis of the lower limbs. Observe first the history and associated risk factors such as smoking, alcoholism, and family history of amputations. When performing the physical examination, observe if the patient is overweight or obese. Then, evaluate the skin of the lower limbs, dryness, fissures, and calluses. Finally, observe pulses from the femoral to the pedis and posterior tibial, and one cannot forget the socioeconomic and cultural evaluation. Complementary studies include continuous wave Doppler, which allows the measurement of the ankle-arm index, where values below 0.9 already indicate a reduction in distal perfusion. In diabetic patients, this generates a problem because the calcification of the arterial wall by the classic Monkberg disease leads to falsely high indices. In this case, it is proposed to measure the pressure in the fingers but, in practice today, there is the ease in performing the triplex Doppler ultrasound that can provide a simple diagnosis (Figures 1 and 2), which is cheap and without risks of obstructive pattern compared with the other standard, that is, the arteriography. Within the vascular physical examination, we can include the medication of the ankle-arm index, the Semmes-Weinstein monofilament test, and the tuning fork. The monofilament test and the tuning fork evaluate neuropathy; however, for the vascular surgeon, this information is paramount, not only for some types of classification of diabetic foot but also for other types of preventive measures that should be taken. In an obese patient with neuropathy, the degree of stress on the supporting structures of the feet is very high, with a reduction of protective mechanisms, leading to plantar ulcers or pruning in cases of claw or hammer finger, and this requires not only visual examination, special insoles, and shoes but also guidance of the patient and the whole family regarding diet, skincare, and visual inspection. In practice, only the clinical examination can define the picture of peripheral arterial disease, and the request of complementary tests such as Doppler ultrasound, computed tomography angiography, and arteriography would be reserved for patients with prediction of possible renovascular or open approach.

Figure 1.

Popliteal artery with triphasic flow.

Figure 2.

Popliteal artery occluded.

Palpation of the pulses:

1. femoral

2. popliteal

3. tibialis anterior – dorsal of the foot

4. tibialis posterior – retromalleolar.

Because clinical examination does not reliably exclude PAD in most people with diabetes and foot ulcers, it is necessary to evaluate the shapes of the arterial Doppler waves at the wrists of the feet in combination with ankle systolic pressure and ankle-arm index (ABI) or measurement of systolic pressure and finger-arm index (FDI). No single modality has proven to be ideal, and there is no defined threshold above which PAD can be safely excluded. However, the diagnosis of PAD is less likely in the presence of ABI values of 0.9–1.3, BDI ≥ 0.75, and three-phase Doppler wave in the wrists of the feet.

5. Classifications used

5.1 Task 2

PAD characteristically presents different patterns according to the fact of associated risk. Thus, in smokers, we observed a greater involvement of the aortoiliac sector. In hypertensive disease, it is the popliteal sector, whereas, in diabetes, it is the infrapatellar pattern with preservation of the fibular artery. From the vascular surgeon’s point of view, the TASK2 classification (Figure 3) can be used, which provides an anatomical evaluation of the lesion site and its extension and may suggest the best endovascular or conventional treatment. With advances in vascular materials and techniques, we are now treating lesions previously indicated for endovascular treatment.

Figure 3.

Task 2 classification.

For the infrapatellar region, the 2015 TASK classification (Figure 4) [15] presents the most common types of patterns seen on angiograms and suggests the best approaches for each. In general, in the infrapatellar region, treatment is indicated in cases of critical ischemia, where the ankle-arm index is usually less than 0.3. In patients with high surgical risk and an ankle-arm index greater than 0.5 with a small wound having adequate perfusion as assessed by a clinical examination or other methods such as TcPO₂ partial oxygen tension greater than 40 mmHg, we evaluate the use of medications combined with hyperbaric oxygen therapy and appropriate dressings.

Figure 4.

Task 2 modified for infrapopliteal segment.

5.2 Fontaine and Rutherford’s classification

The Fontaine classification (Table 1) is used to classify ischemic limbs in general, regardless of etiology. This old classification is well known by vascular surgeons in general, is learned early in residency, and is greatly important because of its ease of use. The Rutherford classification provide a 6-category differentiation in ischemic symptoms with 5 and 6 corresponding to grade 4 in Fontaine’s classification.

Stage	Clinical presentation	Grade	Category	Clinical presentation
I	Asymptomatic	0	0	Asymptomatic
IIa	Mild claudication	I	1	Mild claudication
IIb	Moderate to severe claudication	I	2	Moderate claudication
III	Ischemic pain at rest	I	3	Severe claudication
IV	Gangrene or ulceration	II	4	Ischemic pain at rest
		III	5	Minor tissue lesion
		III	6	Major tissue lesion

Table 1.

Classification of Fontaine and Rutherford’s for chronic peripheral arterial disease.

5.3 WIfI classification

From the initial physical examination and anamnesis, we have prioritized the etiologic and anatomic diagnosis to evaluate the best treatment and means of prevention, which are important to classify the patients; now, we have excellent classification systems. Today, the WIfI classification (Tables 2–4) is considered one of the best in guiding the best treatment and defining the severity of the ischemic diabetic foot.

Ulcer graduation	UPD Gangrene
0	No ulcer without gangrene; Clinical description: small tissue loss. Recoverable with simple digital amputation (1 or 2 fingers) or coating with the skin.
1	Distal superficial small ulcer(s) without gangrene on the leg or foot; without bone exposure, unless limited to the distal phalanx; Clinical description: small tissue loss. Recoverable with simple digital amputation (1 or 2 fingers) or skin coating.
2	Deeper ulcer with bone exposure, gangrene limited to the finger joint or tendon; usually not involving the heel; heel ulcer, without calcaneal involvement; Clinical description: large loss of recoverable tissue with multiple finger amputations ≥3 or standard transmetatarsal (TMJ) amputation ± skin lining.
3	Extensive and deep ulcer involving the forefoot. Extensive gangrene involving the forefoot and/or midfoot; deep and/or midfoot heel ulcer; heel necrosis; and ± involvement of the calcaneus extensive and ± involvement of the calcaneus Clinical description: extensive loss of tissue recoverable only with a complex reconstruction of the foot or nonstandard TMJ (Chopart or Lisfranc); skin flap or the need for managing; complex ulcers for large defects of soft tissues.

Table 2.

WIfI classification. Wound from WIfI system.

Ischemia grade	Ankle-brachial index	Ankle systolic pressure mmHg	Toe pressure, transcutaneous oxygen pressure mmHg
0	≥ 0.80	>100	≥ 60
1	0.6–0.79	70–100	40–59
2	0.4–0.59	50–70	30–39
3	≤ 0.39	<50	<30

Table 3.

WIFI classification. Ischemia from WIfI system.

0	No symptoms or signs of infection; Infection present, as defined by the presence of at least two of the following: local swelling or hardening erythema >0.5 to ≤2 cm around the ulcer tenderness or pain at the site heat on site purulent exudate (thick, opaque to white or bloody discharge)
1	Local infection involving only the skin and subcutaneous tissue (no involvement of deeper tissues and no systemic signs, as described below).
2	Exclude other causes of the cutaneous inflammatory response (e.g., trauma, gout, Charcot’s neuro-osteoarthropathy, fracture, thrombosis, venous stasis).; Local infection (as described above) with erythema >2 cm or involving deeper structures of the skin and subcutaneous tissues (e.g., abscess, osteomyelitis, septic arthritis, fasciitis), and; No signs of systemic inflammatory response (as described below).
3	Local infection (as described above) with signs of SIRS, manifested by two or more of the following findings: temperature > 38°C or < 36°C Heart rate > 90 beats/min respiratory rate > 20 breaths/min or PaCO2 < 32 mmHg leukocyte count >12,000 or < 4000 cus/mm or 10% of immature forms (band)

Table 4.

WIFI classification. Foot infection from WIfI system.

When evaluating the optimal revascularization technique for each case, both bypass and endovascular techniques must consider distal outflow as a crucial factor. According to the JVS guideline [16], it is recommended to measure hemodynamic tests, such as hallux pressure. GLASS (Global Limb Anatomic Staging System) evaluates the TAP (Target Artery Path), which is a direct arterial route from the run-off to the area of interest to be revascularized, with the aim of achieving the best possible limb-based patency (LBP). Thus, in addition to the classifications for diabetic foot and degrees of ischemia, there is the GLASS (Global Limb Anatomic Staging System) scheme (Figures 5 and 6). This scheme assesses the best direct run-off route to a distal lesion, and in certain cases aims to revascularize a corresponding angiosome. It is important to note that a patent TAP (Table 5) is responsible for distributing blood to all the structures of the foot. On the other hand, an incomplete TAP can impede wound healing, even when the corresponding angiosome is used to revascularize the foot [17]. Troisi et al. compared tissue healing, healing time, and survival with PA patency.

Figure 5.

Femoropopliteal (FP) disease grading in global limb anatomic staging system (GLASS). Trifurcation is defined as the termination of the popliteal artery at the confluence of the anterior tibial (AT) artery and tibioperoneal trunk. CFA 1/4 common femoral artery; CTO 1/4 chronic total occlusion; DFA 1/4 deep femoral artery; pop 1/4 popliteal; SFA 1/4 superficial femoral artery. (Conte, Bradbury e col., 2019).

Figure 6.

Infrapopliteal (IP) disease grading in global limb anatomic staging system (GLASS). AT 1/4 anterior tibial; CTO 1/4 chronic total occlusion; TP 1/4 tibioperoneal. (Conte, Bradbury et al., 2019).

Infra-malleolar/Pedal descriptor
P0	Target artery crosses ankle into foot, with intact pedal arch
P1	Target artery crosses ankle into foot; absent or severely diseased pedal arch
P2	No target artery crossing ankle into foot

Table 5.

(Conte, Bradbury, et al., 2019).

GLASS includes the complexity of arterial disease in the distal bed and grades the femoro-popliteal and infra-popliteal segments on a scale of 0–4. This is then plotted on a predetermined matrix based on scientific evidence, resulting in a GLASS combination ranging from 1 to 3. In terms of inflow, GLASS evaluates calcified or non-calcified aortoilic lesions dichotomously.

Aorto-iliac (inflow) disease staging in GLASS.

1. Stenosis of the common and/or external iliac artery, chronic total occlusion of either common or external iliac artery (not both), stenosis of the infrarenal aorta; any combination of these

2. Chronic total occlusion of the aorta; chronic total occlusion of common and external iliac arteries; severe diffuse disease and/or small-caliber (<6 mm) common and external iliac arteries; concomitant aneurysm disease; severe diffuse in-stent restenosis in the aortoiliac system

The success of revascularization depends on various factors, which differ depending on whether it is a bypass or an endovascular method. In the case of a bypass, a good conduit, inflow and outflow are necessary, and the patient must be in good clinical condition to undergo surgery [18].

For endovascular interventions, it is crucial to assess the degree of atherosclerosis and anticipate any problems with the TAP that could jeopardize the direct arterial line to the foot. If the TAP has serial lesions, the success of the procedure will depend on the ability to bypass these lesions.

It is important to note that the artery chosen as the TAP for a bypass may not always be the same for an endovascular intervention (Figure 7).

Figure 7.

WIFI classification. WIfI prediction tables. a. Estimaterisk of amputation at 1 year for each combination. b. Estimate likelihood of benefit of/requirement for revascularization (assuming infection can be controlled first).

In the context of malleolar infarction disease, GLASS has three levels to describe the arteries that cross the ankle. GLASS also makes the following assumptions:

• Restoring durable (pulsatile) in-line flow to the affected. Part, particularly in patients with tissue loss, is a primary goal of revascularization in CLTI.

• Using high-quality imaging (Section 3), the vascular specialist chooses and defines a TAP that is most likely to achieve that in-line flow.

• The TAP will usually involve the least diseased IP artery.

The peripheral arteries (PA) can be classified as complete, incomplete, or absent, with only collateral branches present, as proposed by the global limb anatomic staging system (GLASS). A PA is considered complete when a branch of the DP artery (dorsalis pedis) connects with a branch of the plantar arteries via the dorsal and plantar metatarsal arteries [19].

Incomplete peripheral arterial occlusion (PAO) occurs when one of the truncal arteries in the foot is absent, such as the dorsalis pedis artery or the plantar arteries, resulting in incomplete blood flow between the anterior and posterior circulation. Alternatively, incomplete PAO can occur when the plantar arteries and DP artery are present but not connected.

Alternative classifications for foot vascularization have been proposed, such as Hofmann et al.’s [20] classification of the distal pedal bed. It is important to note that these classifications differ from Rutherford’s.

This classification includes three types:

1. type 1 – flows into the dorsal artery of the foot or plantar region, without representation of the popliteal artery (PA).

2. type 2 – partial representation of the PA, but no connection between the dorsal and plantar regions.

3. type 3 – complete representation of the PA.

Therefore, it is crucial to conduct a preoperative assessment of the foot’s vascularization to determine the appropriate revascularization surgery and predict wound healing [21, 22].

6. Treatment

When faced with a patient with decompensated ischemia who presents with ischemic pain at rest and tissue loss, the possibility of performing invasive procedures to revascularize the limb is evaluated. Conventional infrainguinal revascularization showed higher morbidity and mortality compared to endovascular treatment, according to the BASIL study [23]. In the case of diabetic patients, we often opt for the endovascular technique because these are mostly infrapatellar lesions, for which endovascular treatment is well established as a first-line option. Every year, new materials and more sophisticated techniques appear, allowing extensive and increasingly distal revascularization even in cases previously considered inoperable. This requires, in addition to a highly trained team, a hospital with an excellent structure and equipment, such as ultrasound in the operating room, high-definition digital fluoroscopy, special guidewires with nitinol bodies, and a heavy weight at the tip to overcome calcified lesions, support catheters, and long and thin balloons to perform the most diverse techniques. The surgeon can choose the anterograde, retrograde, or both approaches, depending on the level of occlusion, the distal artery, and the type of plaque. Another technique widely used in severely calcified arteries where the anterograde route is more difficult to recanalize is the technique of distal micropuncture of the pedal or posterior tibial artery. Today, very thin balloons of up to 1.5 mm are used to dilate the arteries of the foot, in addition to providing support for the guidewire as it advances. Through the concept of angiosome, we should aim to take the pulsatile blood to the most distal regions possible and preferably to the site that directly irrigates the necrotic area, having as a goal the complete revascularization of the plantar arch leaving blood to the toes and perforating branches that irrigate the forefoot, dorsal region of the foot, and calcaneus posteriorly. In terms of techniques used to overcome the lesions anterogradely, we have the technique of using guide wires under a 0.014 catheter to try to slide through the occlusion intraluminal, called the sliding technique. If not effective, we can use guide wires with a thinner, heavier tip and rotate them to perforate the proximal rigid plate (cap), known as the drilling technique. A form of treatment that was once considered only for the supra-patellar area and can now be performed in the infrapatellar area is the subintimal recanalization technique, which requires great technical skill in addition to 0.018 guide wires [24]. According to the 2019 edition of the International Working Group on the Diabetic Foot (IWGDF), patients with ankle pressure < 50 mmHg or ITB <0.5 should undergo vascular imaging for possible revascularization, as well as those with toe pressure < 30 mmHg or PtcO₂ < 25 mmHg. Physicians may consider revascularization at higher pressure levels in patients with extensive tissue loss or infection [3]. Classically, the goal of successful revascularization is to deliver pulsatile flow directly to the site of ischemic tissue damage. However, the angiosome approach has recently been proposed as a topic of debate. This theory posits that the foot can be divided into three-dimensional blocks, each with its arterial supply. Direct revascularization results in the restoration of pulsatile blood flow through the supply artery to the area where the ulcer is located. In contrast, indirect revascularization restores flow through collateral vessels derived from nearby angiosomes. Targeting revascularization to the vessel directly supplying the anatomic area (angiosome) where tissue loss has occurred is a more effective method of revascularization than simply targeting the best vessel, which may not supply enough blood to the area where tissue loss has occurred. A recent retrospective analysis of endovascular attempts to salvage limbs in patients with peripheral artery disease revealed that indirect angiosome revascularization was linked to poorer outcomes when compared to direct revascularization.

In cases of arterial obstructions, optimal operative planning should be carried out before proposing treatment. In this case, the access route should be well evaluated based on the obstructive pattern, the patient’s physical complexion, and the team’s experience. Normally, access to endovascular treatment is via the common femoral artery using the Seldinger technique, either anterograde or retrograde. Today, in some cases, retrograde podal access is used that facilitates the recanalization of distal calcified lesions as the distal region of the obstruction tends to be softer, avoiding the proximal calcium layer. Regarding the material to be used, the ideal is to have a wide range of materials available, including 0.014 guide wires with a high tip weight, such as the Abbott Command® and a support catheter such as the Trailblazer® or Quickcross®. Peripheral artery disease in patients with diabetes has several characteristics that render it more difficult to treat. The atherosclerotic lesions are multilevel and particularly severe in tibial arteries, with a high prevalence of long occlusions. The predilection for multiple crural vessel involvement combined with extensive arterial calcification increases the technical challenges associated with revascularization using either open bypass or endovascular techniques. In the last decades, new techniques and technologies have been introduced for treating PAD, which might be relevant to patients with diabetes and poorly healing ischemic foot ulcers. Encouraging results have been reported on endovascular approaches, and the field is rapidly evolving [25]. Today, the use of ultradistal revascularization techniques at the level of the plantar arch is made possible using thin 1.5-mm balloons under guide wires and combined retrograde and anterograde puncture techniques, as well as auxiliary techniques such as atherectomy and subintimal re-entry catheters. The goal of revascularization is to restore online flow to at least one of the arteries in the foot, preferably the artery supplying the anatomic region of the wound. However, evaluating the benefit of revascularization in patients to whom the risk-benefit ratio for the likelihood of success is unfavorable. Evaluate the distribution of PAD, the availability of an autogenous vein, the patient’s comorbidities, and the operator’s experience, as well as the available materials and hospital support structure. Lower extremity ischemia affects the healing potential of a foot ulcer. If ischemia is identified during assessment, its treatment should always be considered. Based on the IWGDF/ESVS/SVS intersocial guidelines [26], the following treatment recommendations are made: In a person with ankle pressure < 50 mmHg or ITB < 0.4, consider urgent vascular imaging, always with detailed visualization of the arteries below the knee and foot, and revascularization. In addition, consider urgent evaluation for revascularization if toe pressure is <30 mmHg or TcpO₂ is <25 mmHg. However, clinicians may also consider revascularization at higher pressure levels in patients with extensive tissue loss or infection, that is, higher WIfI scores. In terms of treatment, there is a classification called Task 2 that provides a guideline for management. The best course of action for each case depends very much on the service, socioeconomic conditions, and clinical aspects of the patient involved. A Task D patient can successfully undergo an endovascular procedure in a hospital with a dedicated team, using state-of-the-art materials and equipment, and with appropriate intensive care support.

Optimized clinical management to reduce the very high cardiovascular risk associated with PAD in people with diabetes (smoking cessation, control of hypertension and dyslipidemia, use of antiplatelet agents, SGLT2 inhibitors, or GLP1 agonists) [27].

The natural history of patients with diabetes, PAD, and foot ulcers remains poorly defined. However, in two studies that reported outcomes in patients with diabetes and ischemia who did not undergo revascularization, the limb salvage rate was approximately 50% at 1 year. After revascularization, most studies report limb salvage rates of 80–85% and ulcer healing rates of greater than 60% at 12 months [26]. In a different situation, for example in a developing country, we may have to indicate primary amputations without being wrong because, without the conditions to perform revascularization with adequate limb salvage rates, we are putting the patient’s life at risk. In this respect, the recent WIfI classification can be considered the most rational, as it assesses the risk of amputation in 1 year, but the good judgment of the medical team is still the determining factor for success. In a recently published meta-analysis combining data from 12 studies (11 prospective and 1 retrospective), the WIfI classification was shown to be a good prognostic method for amputation at 1-year follow-up. A positive statistical correlation was observed between stage progression (from 1 to 4) and increased incidence of amputation [28].

As the level of heterogeneity was very high because of differences between studies (mainly population characteristics, inclusion criteria, and endpoint), the level of evidence was considered low or very low depending on the stage, and it was not possible to demonstrate the usefulness of using the WIfI classification for clinical practice, that is, for recommending limb revascularization. Specifically for diabetic patients, a very important correlation has been identified, with wound healing proving to be more relevant than direct revascularization (guided by the angiosome) or assessment of the quality of the plantar arch [29].

One of the weaknesses identified in the meta-analysis of the WIfI classification was the inadequate correlation because it does not take into account the anatomical state of the arterial circulation. Thus, nonrevascularization was considered only because it was impossible (clinically or anatomically), and not because it might be necessary. The combination of the WIfI classification with a classification that assesses anatomical impairment would have the role of assessing the patient globally to better support the indication of revascularization [30].

The wide variety of lesion distributions in DM patients requires the use of devices that can be effective in endovascular treatment of tortuous arteries in the aortoiliac of the aortoiliac segment, femoropopliteal arteries and, above all, stenoses of infrapopliteal and inframalleolar arteries. The infrapopliteal vessels are affected in more than 70% of patients [2, 31].

The conventional balloon in long lesions has relatively low patency rates, ranging from 25 to 40% at 1 year. After balloon inflation, they can lead to elastic retraction dissection and therefore dissection, resulting in high rates of stenting after angioplasty (bailout). Still, about angioplasty balloons, new types with different design features have recently been introduced with the aim of improving angioplasty outcomes. These devices appear to reduce the incidence of restenosis and flow-limiting dissection and may increase the ability to fix drugs in pharmacological balloons [32, 33].

Cases such as this may require the use of atherotomes aiming at plaque reduction and better preparation of the lesion for subsequent angioplasty with a drug-eluted balloon.

If endovascular revascularization is indicated, it may be necessary to bypass the lesion via the subintimal (Bolia) or intraluminal route, in which case techniques such as POBBA may be required, requiring materials such as atherotomes, support catheters, high-pressure balloons, and stents. The use of stents in the popliteal artery is problematic because it is an area that is subject to various stresses that can lead to stent fracture. In addition to the use of endoluminal techniques with support catheters and atherotomes, retrograde recanalizations are very useful, and the new stents for this region, such as Supera®, have become indispensable.

In the case of associated infrapatellar occlusion, if the lesions are short, there is usually no great difficulty in bypassing these lesions anterogradely using simple or pharmacologically thin balloons. It is important to keep the balloon inflated for approximately 3 min to ensure good impaction of the plates on the wall. Associated anterograde/retrograde techniques, as well as others such as subintimal techniques, have led to success in situations that were previously virtually impossible to treat endovascularly. In any case, we should evaluate distal bypasses within situ, reverse, or ex vivo devolved saphenous veins, which have high patency rates but require a refined technique and the use of autologous grafts in good condition and, of course, a good distal bed to receive the flow.

Patients with diabetes and ischemia represent a subgroup with a worse prognosis, thus, the angiosome model proposed by Jan Taylor in 1987 has reappeared as a target to be achieved in order to obtain favorable results [30].

In the original article by Prof. Jan Taylor [26], he first stated that the angiosome corresponds to a volumetric block of subcutaneous cellular tissue and skin with a single, specific venous and arterial irrigation and with extensive collateral communication between adjacent angiosomes.

This has been adapted to the ischemic diabetic foot in the planning of surgical and endovascular revascularization procedures in patients with Stage III and IV Rutherford classification. The model defines six angiosomes for the foot, divided by the territory of the tibial and peroneal arteries. The medial calcaneal artery and the medial and lateral plantar arteries, which are the branches of the posterior tibial artery, would each irrigate three angiosomes. The pedicle artery, the terminal branch of the anterior tibial artery, would flush another angiosome; and the lateral calcaneal and lateral perimalleolar arteries, which are branches of the peroneal artery, would flush the final two angiosomes in the foot. In the ankle, there are also angiosomes in the territory of the lateral malleolar artery (branch of the anterior tibial artery), which also give off median malleolar branches, and the angiosome of the anterior perforating artery (branch of the peroneal artery (Table 6 and Figure 4).

Location of the ischemic lesion	Arterial territory to revascularize
Calcanean	median calcaneal artery (branch of the posterior tibial artery) lateral calcaneal artery (branch of the peroneal artery) collaterals between the two anterior territories
Posterolateral side of the ankle and perimalleolar	median perimalleolar network anterior perforating artery (branch of the peroneal artery) anterolateral malleolar branches (branches of the anterior tibial artery)
Plant	median and lateral plantar arteries (branches of the posterior tibial artery) tarsal arteries (branches of the pedicle artery)

Table 6.

Revascularization strategy based on the location of ischemic lesions.

Several studies have shown that using the angiosome concept, limb salvage rates with direct revascularization techniques are significantly better than with indirect revascularization techniques [34]. An article by Iida et al. showed worse results in limb salvage rates in diabetic patients with elevated CRP, possibly due to increased blood demand. Indirect revascularization without direct pulsatile flow to the angiosome in question was observed. The results of this article would lead to the conclusion that in Rutherford 5 and 6 patients, indirect or direct revascularization would lead to similar results, except in patients with diabetes and wound infection, where direct revascularization in the angiosome leads to significantly better results [35]. Another study by Kahn et al. suggests always try to revascularize as many infrapatellar arteries as possible in patients with diabetes and distal necrotic lesions, regardless of the angiosome of the lesion, to promote overall improvement of foot perfusion pressures at the microcirculatory level leading to better outcomes [36]. The figures below show arteriograms of diabetic patients with infrapatellar artery occlusion. The arteries to be recanalized were indicated (Figures 8–12). This is a case of a patient with a trophic lesion of the hallux, insulin-dependent diabetes mellitus, and ischemic pain at rest. The arteriography showed a patent fibular and occlusion of the anterior and posterior tibial arteries. In this case, we opted for foot amputation and clinical management because of the presence of extensive collateral circulation, a distal Tcpo2 above 40 mmHg, and the availability of hyperbaric oxygen therapy and a dressing team.

Figure 8.

Example of popliteal occlusion with calcified plaque and occluded stent in popliteal artery.

Figure 9.

Angiosome distribution in the foot.

Figure 10.

Image of infra popliteal vessels and distal runnoff, with occlusion of anterior and posterior tibial arteries.

Figure 11.

Image of infra popliteal vessels and distal runnoff, with occlusion of anterior and posterior tibial arteries and and refilling of distal collaterals by the distal branches of the peroneal artery.

Figure 12.

Image of pedal arteries with dorsal pedis artey and incomplete pedal arch.

The effectiveness of a revascularization procedure should preferably be assessed with objective perfusion measurements. After revascularization of a limb with an ischemic lesion, it is recommended to wait approximately 2 weeks, if possible, before performing minor amputations or debridements due to the progressive increase in tissue oxygen tension after angioplasty.

7. Conclusions

When we studied the articles on the application of the angiosome concept to the ischemic diabetic foot, we observed a great concern to reduce the MALE and save the limb, and it is necessary to consider not only the anatomical aspects but also the functional aspects of the patient and the institution. The treatment of the diabetic foot will always be multidisciplinary. The vascular surgeon should be responsible for the final treatment strategy aimed at saving the foot in advanced stages. The clinician, physiatrist, physiotherapist, and dietician should be responsible for preventive issues. Finally, the patients themselves and their family members should be trained to recognize early changes that indicate decompensation of the diabetic foot.