A number of systemic conditions can lead to lower extremity ulcers. The most common etiology is vascular, such as peripheral arterial disease or venous disease. By the time a patient develops an ulcer, the vascular disease process is well under way.
Peripheral arterial disease is a slow and insidious disease process that affects an estimated 8 to 12 million Americans, and the incidence continues to increase yearly. 1,2 As many as 20% of Americans over age 65 are affected by peripheral arterial disease; of those, only 25% receive treatment. 3 Many individuals with peripheral arterial disease are asymptomatic. An estimated 10.5 million of those with the disease are symptomatic; another 16.5 million are asymptomatic. 2 Results of studies on lower extremity ulcers report a prevalence ranging from 0.12% to 1.8%. 4
Diagnosis of the disease is often overlooked because patients and primary care providers (PCPs) are unaware of the disease in its early stage. It has been shown that PCPs have little knowledge of peripheral arterial disease and treatment. 5 Better education about peripheral arterial disease would equip PCPs to assess and diagnose patients early, before the disease becomes limb-or life-threatening.
ANATOMY AND PHYSIOLOGY OF THE LOWER EXTREMITY ARTERIAL SYSTEM
Arterial perfusion begins with the heart. Blood exits the heart from the left ventricle into the thoracic aorta, then into the abdominal aorta. Intercostal and lumbar arteries extend from the abdominal aorta (Figure 1). The aorta divides at the level of the umbilicus to form the common iliac arteries. These arteries divide again to form the internal and external iliac arteries. The internal iliac arteries supply blood to the sigmoid colon and rectum. At the inguinal ligament, the external iliac artery becomes the common femoral artery.
The common femoral artery divides into the superficial femoral artery—the most frequent site of occlusion in peripheral vascular disease—and the deep femoral artery. The superficial femoral artery becomes the popliteal artery, which divides into 2 arteries just below the knee: the tibioperoneal trunk and the anterior tibial artery. The anterior tibial artery becomes the dorsalis pedis artery in the foot.The tibioperoneal trunk divides into the peroneal artery and the posterior tibial artery. The posterior tibial artery supplies the plantar arch, which perfuses the heel and sole, and then branches to the toes. The anterior tibial artery completes the arterial communication as it joins the plantar arch.
PATHOPHYSIOLOGY OF ARTERIAL ULCERS
Insufficient arterial flow to tissues causes ischemia and eventually necrosis, resulting in arterial ulcers 7 (Figure 2).These ulcers account for approximately 20% of all leg ulcers. Arterial insufficiency may be acute or chronic, and occlusion may occur in a single artery or in more than 1 vessel along the arterial tree. Atherosclerosis is the most common cause of arterial ulcers. Atherosclerosis is a chronic, progressive disease involving the deposition of cholesterol along the lining of the vessel wall. Eventually, the vessel lumen narrows enough to affect blood flow. Areas affected by atherosclerotic plaque have the greatest turbulence because of the restricted blood flow. Other arterial vascular diseases that may cause ulcers include vasospastic disease (Raynaud syndrome) and vasculitis (rheumatoid diseases).
Acute arterial ischemia is most commonly associated with an embolic event. Part of a plaque is dislodged from the arterial wall and is forced into the smallest artery that will accommodate it. The tissue distal to the embolism, previously fed by the artery, becomes ischemic, then necrotic.
Arterial ulcers are frequently found at the most distal point of arterial perfusion. The tip of the toe is a common place for ulceration, particularly if there has been any pressure from footwear or other trauma. Location may be misleading in some cases; any trauma to the foot or lower leg can precipitate an injury that will be called an arterial ulcer if blood supply to the area is reduced.
A pure arterial ulcer often has no edema, unless the patient with pain at rest keeps the leg dependent throughout the night for comfort. The clinical appearance of a pure arterial ulcer is a pale, dry base with surrounding shiny skin. If atherosclerosis has been present for a long time, hair loss will be evident. The presence of hair does not rule out an arterial ulcer, however. No drainage is apparent unless the ulcer is infected. The ulcer base may have a yellow film across the surface. Arterial ulcers have been described as having a “punched out”appearance, which is caused by the ulcer borders having a clear demarcation from the adjacent tissue. Without cellulitis or infection, the surrounding tissue is usually not inflamed (Table 1).
Pain associated with the ulcer, which may be described as burning, occurs with dressing changes and handling. Pain is diminished or absent if the patient has diabetic neuropathy. The ulcer base may be covered with a black dry eschar.
ASSESSMENT OF ARTERIAL DISEASE
History and physical examination
Obtaining a complete and comprehensive patient history is crucial. Symptoms in a patient with chronic lower extremity arterial insufficiency include pain, described as cramp-like sensations in the calf when walking (known as claudication). The pain occurs in the muscle group distal to the stenosed or occluded artery. Although the calf is the most commonly affected location, claudication can also occur in the buttock, thigh, or foot. If the cramping is relieved when the patient stops walking; no other intervention is needed. If the patient must sit or perform other maneuvers to reduce the pain, another cause for the pain must be ruled out (Table 2).
As arterial disease progresses, the pain pattern will change. Instead of pain when walking, pain in the foot or toes will occur at night, when the patient is lying flat and the blood pressure is lowered to meet the basal metabolic needs. The pressure required to traverse an arterial stenosis and perfuse the distal tissues of the foot may not be met. Distal tissue becomes ischemic and the pain wakes the patient from sleep. This is known as rest pain, and it generally signals a threat to survival of the affected limb.
Patients with rest pain often report that getting out of bed and walking helps relieve pain, in contrast to patients in earlier stages of the disease who experience pain with walking. A different mechanism is in place with rest pain: Gravity is used to increase flow to the distal tissues and to reduce pain.
Arterial disease manifests in many different end organs. Atherosclerosis in the carotid or vertebral artery may cause cerebral or cerebellar symptoms, such as transient ischemic attack or stroke. In the coronary arteries, the same disease leads to myocardial infarction; it causes renovascular hypertension in the renal arteries. In the lower extremities, arteriosclerosis causes ischemia of the calf muscles during ambulation. Atherosclerosis is primarily seen in older patients. In many cases, these patients have comorbid conditions that prevent them from walking to the point of claudication.
Patients should remove shoes and socks for foot examinations when visiting their PCPs. If the patient presents with a unilateral leg or foot ulcer, the other foot should also be examined. Atherosclerosis does not occur in isolation in one part of the body; however, it may manifest in one location before symptoms occur in another area. The examination provides an opportunity to compare the extremities, and to detect potential problems in other areas.
Skin, nails, and hair
Classic textbook descriptions of the foot with arterial peripheral vascular disease indicate that the skin is hairless and the nails are thickened. Thick nails usually occur because of a fungal infection, and arterial disease can be present without hair loss. In an older patient, hair loss may occur strictly as part of the aging process. An acute arterial occlusion will not have an immediate effect on the hair or nails.
Inspecting the skin is an important part of the clinician’s assessment because skin color may provide an indication of arterial perfusion. Ischemic tissue appears pale, then mottles and becomes dark purple as ischemia progresses. Finally, the skin turns black with tissue death. When chronic arterial insufficiency is present, the skin is taut, thin, and shiny.
During the examination, the clinician should palpate the skin for temperature changes. Ischemic tissue is noticeably cooler than the surrounding skin or the contralateral limb.
Pallor and dependent rubor
In the patient with arterial insufficiency, the skin of the affected extremity will be pale when the extremity is elevated to 45 degrees. With the foot in this position, test the patient’s capillary refill by compressing the pad of the great toe between the forefinger and thumb. Capillary refill time should be less than 3 seconds in normal tissue. Longer refill indicates decreased perfusion.
When the affected extremity is placed below the level of the knee (dependent position), the foot becomes dark red or ruddy. This is known as dependent rubor or reactive hyperemia. It occurs because gravity is helping the capillaries fill with blood when the foot is in this position.
Pulses and pressures
Pulses are diminished or absent in the presence of arterial insufficiency. Pulses that are palpable in the foot while the patient is at rest or with the leg in a dependent position may disappear when the patient exercises. Individuals reporting claudication symptoms with palpable pulses should have their pulses reassessed after exercise.
Blood pressure is significantly reduced in the ischemic lower extremity. The ankle-brachial index (ABI) is the standard of practice to evaluate blood pressure in a patient with suspected peripheral arterial disease (Table 3). Any clinician can perform this test in an office. 12,13
The ABI results are compared with the patient’s physical signs and symptoms. A normal ABI is 1; that is, in patients without arterial disease, the pressure at the ankle should be the same as the brachial artery pressure with the patient in the supine position. If the ABI is between 0.80 and 0.90, there is some arterial insufficiency but usually not enough to cause symptoms. An ABI between 0.41 and 0.80 correlates with claudication; an ABI below 0.40 correlates with rest pain.
Patients presenting with an arterial ulcer should be tested for decreased sensation in the feet. Neuropathy, which may have contributed to ulcer development, is a frequent symptom in patients who have diabetes and arterial insufficiency. The most common and reliable test for assessing sensory impairment in the foot is use of the Semmes-Weinstein monofilament.
Noninvasive vascular laboratory and invasive arteriogram tests provide objective correlation with the assessment. Besides the ABI, noninvasive tests include the Doppler ultrasound, segmental pressures and waveforms, duplex ultrasound, and transcutaneous oxygen pressure.
A Doppler ultrasound distinguishes arterial flow patterns by sending a signal that is reflected to the probe. When the signal strikes the moving red blood cells, a frequency shift is reflected as sound. The Doppler shift recording demonstrates the normal arterial signal as 3 phases of the pulsation. The first wave is upward, representing forward blood flow and arterial distention. The second phase, below the baseline, represents arterial relaxation and subsequent retrograde blood flow. The third phase is believed to represent bulging of the aortic valve, which occurs during diastole. The third phase is lost first as the atherosclerotic artery becomes less compliant. As arterial disease worsens, the first wave becomes broad and dampened (Figure 3).
Segmental pressures are obtained bilaterally on the lower extremities at the thigh, above the knee, the calf, and the ankle. Pressures are compared from one limb to the other. A 20 mm Hg variation in pressures can identify the location of an arterial lesion.
With arterial insufficiency, the treatment goal is preservation of viable tissue. Along with the external ulcer, the internal arterial lesion must be treated. In fact, the ulcer is unlikely to heal if adequate arterial perfusion is not established. Surgery or a percutaneous procedure may be recommended to restore blood flow, based on noninvasive tests and contrast arteriograms.
Treatment recommendations should consider the patient’s prognosis, functional ability and life expectancy, relative risk of the proposed treatments, arterial outflow, and lesion morphology.
Medical treatment for atherosclerosis includes medications such as platelet inhibitors, antilipid medications, and angiotensin-converting enzyme inhibitors. Although medications are an important part of preventing and treating atherosclerosis, they have a minimal role in treating an arterial ulcer.
Surgical treatment: Revascularization
An arteriogram will identify specific stenoses and open outflow vessels. Bypass grafting is the standard surgical intervention. Grafts may be made of prosthetic material or autogenous veins. Autogenous veins may be in situ or reversed veins.
Percutaneous angioplasty and stent placement are also performed in some cases, but they are not as durable as a bypass graft. Aortoiliac bypass, femoral-popliteal bypass, and distal bypasses are the primary types of operations for arterial insufficiency. In patients with multilevel disease, the most proximal lesion is treated first to establish adequate inflow into the limb. This may provide sufficient blood flow to heal the wound.
Another goal is use of an adequate target vessel as the point of termination of the bypass conduit. Whenever possible, this target vessel should be in direct continuity with the area of tissue loss or ischemia. If a target vessel is unavailable, a second choice may be a vessel whose collaterals provide perfusion to the area.
Interestingly, percutaneous procedures have not resulted in the cost savings that were expected when compared with bypass procedures.
Advantages and disadvantages of open surgical bypass operations
Vascular surgeons have routinely performed an open form of arterial bypass for more than 20 years. The results and durability of these procedures are indicated in Table 4. An open bypass procedure generally establishes direct pulsatile flow to the area of tissue loss. This is required to heal ischemic wounds.
The obvious disadvantage of major bypass surgery is the length of time it takes (4 to 6 hours for a bypass to the level of the ankle) and its complexity. The incisions are long and the hospital stay for this procedure may be 7 to 8 days. Another disadvantage of this operation is that a usable autogenous venous conduit must be used; the most common is the ipsilateral greater saphenous vein. This vein may be absent, however, because of prior coronary artery bypass grafting, or it may be too small to use.
The general morbidity and mortality associated with these procedures ranges from 10% to 15%, if all possible complications are combined. Therefore, on average, 85% to 90% of procedures can be performed successfully with subsequent limb salvage.
After a successful operation, the patient requires routine surveillance of the bypass conduit throughout his or her lifetime. This ensures that graft patency is not threatened by intimal hyperplastic lesions or progression of atherosclerosis. Many of these patients require additional limited operations to maintain an adequate conduit. Although patency rates may be as low as 75% at 4 years for certain procedures, the limb salvage rate in these patients is usually in excess of 90%.
Advantages and disadvantages of percutaneous procedures
Within the last 10 years, angioplasty and other nontraditional treatments have become available. In general, percutaneous procedures are less durable than the traditional bypasses they were intended to replace. Nonetheless, under the appropriate indications, percutaneous procedures provide an excellent adjunct in patient care, especially in very high-risk patients who may not be surgical candidates.
Again, the treatment goal is to provide pulsatile arterial flow to the level of the ischemic wound. A variety of balloons and stents are available. The use of angioplasty procedures in the common iliac arteries rivals the patency rates and durability of aortobifem bypass grafts. However, distal to the inguinal ligament, the durability of angioplasties with or without stent placements pales in comparison with the open technique. Newer techniques and stents covered with thin prosthetic material are showing some promise of durability. The combination of angioplasty with or without stent placement and subsequent distal use of a vein for a bypass may be used in patients with limited vein length. Lytic agents may help recannulate a recently occluded target vessel, allowing a more distal bypass to help provide adequate perfusion to the level of ischemia.
When used in conjunction with a bypass, these adjunctive measures provide numerous options to surgeons practicing limb salvage procedures. The obvious advantage of percutaneous procedures is that they do not require a major operation and recovery is swift. Many of these procedures are performed in an outpatient setting, and the patient can resume normal activity in 24 hours.
However, none of these procedures are without risk. Routine angioplasty carries about a 5% major risk of arterial complications including rupture of the artery, dissection of the artery, some occlusion of the vessel, and associated problems with the contrast agent that is required (such as renal failure, allergic reactions, and arterial injury from the puncture site).
With competent physicians performing percutaneous procedures, the morbidity and mortality is usually less than that of a comparable open operative procedure. But if a patient has some degree of renal impairment and is not yet in end-stage renal failure, the contrast agents may cause permanent renal damage. Because of this high risk, some of the patients who would most benefit from these procedures may not be candidates. In addition, the dye load used can be very hypertonic and may cause the patient to develop congestive heart failure from the sudden increase of intravascular volume.
Considering the advantages and disadvantages of the open procedure and the percutaneous procedure, appropriate patient selection is key. Not all patients require a bypass down to the level of the medial malleolus, or even the plantar arch, to be patent for life. Many times, adequate pedal perfusion, achieved by any technique, for long enough to allow the wound to heal will result in adequate percentages of limb salvage. That, of course, is the treatment goal.
Patients who are not candidates for arterial bypass procedures may benefit from use of an intermittent compression device (Art Assist; ACI Medical, San Marcos, CA) prior to considering amputation. This device—consisting of an external pneumatic device and a calf pump—stimulates skin perfusion in the foot in patients with peripheral arterial disease. The patient, who can use the device while sitting, places a cotton sock over his or her foot before the cuff is placed. The pump applies 120 mm Hg pressure, beginning at the foot and compressing sequentially to the ankle and the calf. The cycle is repeated 3 times every minute. Recommended use of the device is 3 times a day for approximately 1 hour. The device is intended to simulate walking. Effects of the device should be noted within 2 weeks, with maximum effect in about 3 months. The device has been shown to increase blood flow in the popliteal artery and at the tissue level. 8–11 Improvements in calf blood flow were observed using noninvasive laboratory tests.
The compression is delivered in short bursts. The veins are almost emptied, reducing venous pressure and causing an increase in the arterial venous pressure gradient, which allows an increase in arterial inflow. Physiologic activities thought to be at work here are a release of nitrous oxide, tissue factor pathway inhibitor, and tPA. A vasodilating effect also occurs.
Treatment of the arterial ulcers is primarily focused on the ulcer etiology, and secondarily on the wound itself. Increasing the blood supply to the wound is the most important treatment. Patient positioning to facilitate blood flow may be helpful. The wound characteristics and the goal for the wound guide the clinician’s product choices. Treatment always includes providing an environment to promote tissue growth, protecting the wound, and preventing further tissue destruction. Unfortunately, arterial ulcers always pose the threat of limb loss.
Debridement of nonviable tissue is performed only after the revascularization procedure, which provides enough blood flow to heal the wound created by debridement. Arterial ulcers and any dry eschar or gangrenous tissue are kept dry until revascularization is performed (Figure 4). If dressings to promote moist wound healing are used in the presence of necrotic tissue and eschar, the dead tissue may become a bed for bacterial growth, allowing the wound and surrounding tissue to become infected.
After the revascularization procedure, the ulcer is treated with dressings that promote moist wound healing, such as moist saline, gels, hydrocolloids, films, and foams (Table 5). When choosing a dressing, focus on protecting the surrounding skin from maceration, filling in a crevice if the wound is deep, and stimulating the growth of granulation tissue and epithelialization. New products are frequently introduced to the market to promote some phase of wound healing, but no clinical trials demonstrate that any one of these products has a significantly better outcome than the others. 14
In addition to revascularization, the wound environment must be maximized and the patient must receive adequate nutrition to support wound healing. 15,16 If the wound continues to deteriorate, the patient should be examined for as-yet unidentified comorbid conditions. The wound should be biopsied to rule out malignant pathology. Administer intravenous antibiotics for infected wounds; topical antibiotics are not indicated in these cases. Wounds with mixed etiology (arterial and venous) should be referred to a vascular specialist. Vascular ulcers differ; treatment for one type may be inappropriate or harmful to another.
When arterial bypass and percutaneous procedures are not viable options for restoring circulation and healing an ischemic ulcer, the patient faces an amputation. Of all the procedures that a vascular surgeon performs, amputation is the only one that is truly curative. An appropriately timed and indicated amputation, be it minor or major, allows the patient closure. The patient can recover and begin living the rest of his or her life, usually without pain.
Amputations are more accepted by the patient if the intended amputation site is causing pain. In patients who have diabetes and neuropathy, pain is frequently absent. For this reason, in the authors’ experiences, these patients are the most difficult to convince of the need and appropriateness for an amputation.
Indications for amputation include uncontrolled infection at the site of tissue loss, uncontrolled pain, or extensive tissue loss, in which local tissue regrowth or adequate tissue coverage is not feasible. The extent of the amputation is decided with regard to rehabilitation and the patient’s abilities. The energy expenditure needed to ambulate with an above-knee prosthesis is far greater than that needed with a below-knee prosthesis. If a patient is a reasonable candidate for prosthetic training, knee joint preservation should be attempted if healing is possible. Even if the patient is not likely to ambulate with a prosthesis, the ability to hook the lower stump over the side of a wheelchair seat and stabilize the seated position makes the below-knee amputation desirable. A bed-bound patient, however, may be better served with an above-knee amputation because these amputations have a higher healing rate than below-knee amputations.
Determining the healing potential of the amputation level can be difficult. Numerous tests are designed to help the guide surgeon, such as transcutaneous oxygen measurements, ABI, toe brachial pressures, laser Doppler blood flow measurements, and dermal xenon perfusion tests. The tests have a drawback, though: They are weighted in favor of a 90% healing rate, which sets the standard too high and condemns many patients to higher levels of amputation than may be necessary.
To date, no highly predictable assessment of healing potential is available. Even a palpable pulse does not assure that a toe amputation will heal.
Patient education is critical in the management of arterial disease and arterial ulcers. Patients who understand the disease process are better equipped to participate in their care. Those who can identify and report significant signs and symptoms are less likely to overlook problems. Charts and diagrams are useful in teaching patients about the arterial system, surgical procedures, and wound healing. Smoking interferes with wound healing and stimulates proliferation of atherosclerosis. Advise patients to stop smoking.
Smoking cessation programs are available through local health care institutions, the American Lung Association, and the American Heart Association for those who seek help to stop smoking. More and more evidence supports the finding that secondhand smoke is just as harmful as direct smoking. Patients and their families should be advised of this information.
Wound healing requires an increase in caloric and protein intake. Remind patients, as necessary, of the importance of good nutrition.
Foot care instructions include wearing appropriate shoes, which should provide support without causing pressure points. Patients should be taught to cleanse the feet well, dry between the toes, and inspect the feet carefully. If the feet are dry, they should be moisturized after washing. Lotion should not be applied between the toes, however, to avoid maceration. A professional should trim the nails if they are thick and hard. Regular use of an emery board can help keep the nails short and smooth.
Patients with peripheral arterial disease will not be cured. Their disease requires lifetime management. This includes regular preventive health care visits with their PCP, and routine follow-up diagnostic testing.
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6. Futterman LG, Lemberg L. Peripheral arterial disease is only the tip of the atherosclerotic “iceberg.” Am J Crit Care 2002;11:390–4.
7. Tyrrell W. The causes and management of foot ulceration. Nurs Stand 2002;16:52–62.
8. van Bemmelen PS, Weiss-Olmanni J, Ricotta JJ. Rapid intermittent compression increases skin circulation in chronically ischemic legs with infra-popliteal arterial obstruction. Vasa 2000;29:47–52.
10. Banga JD, Idezerda JG, Eikelboom BC. Intermittent compression therapy in patients with leg ischemia. 17th World Congress, International Union of Angiology, April 1995.
11. Eze AR, Comerota AJ, Cisek PL, et al. Intermittent calf and foot compression increases lower extremity blood flow. Society for Clinical Vascular Surgery, 24th Annual Symposium on Vascular Surgery, March 1996.
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When taking a history, it is important to ascertain exactly how far the patient can walk before needing to stop; a shorter distance indicates more severe atherosclerosis. Reported changes in ambulatory distance may indicate progressive atherosclerotic disease.
The best way to document pulses is to use descriptor terms, such as present or absent, rather than numerical ratings, such as 2+ or 3+. Use modifier words, such as weak or bounding, to further describe and clarify the pulse findings.
The preferred attachment device for dressings on vascular leg ulcers is roller gauze or commercial devices (such as netting or tube gauze) that hold dressings in place without adhesive, which can damage fragile skin.