By Timothy K. Fisher, DPM, and David G. Armstrong, DPM, MD, PhD
People with diabetes face the possibility of developing a variety of diabetic complications, with the risk of each dependent on a number of factors including, first and foremost, blood glucose control. One area in which complications can occur is the feet. It is estimated that as many as 25% of people with diabetes develop a foot ulcer at some point in their lives, and ulcer risk tends to increase with age. The major contributing factor to this risk is loss of sensation in the feet, usually caused by peripheral neuropathy, or nerve damage in the feet and legs. This common complication can change or reduce the sensation of pain, heat, and cold in the feet. For example, if someone with neuropathy were to walk on hot pavement, he might not be able to feel the heat, so there would be an increased likelihood of burns or blisters — which, in turn, could easily go unnoticed and untreated due to the lack of sensation.
Add to the mix another common diabetic complication: reduced blood circulation in the limbs, or peripheral arterial disease. Blood is the main source of oxygen and other nutrients essential to healing, as well as immune defense, so when circulation is impaired, wounds tend to take longer to heal and are more likely to become infected.
Thus, for feet, the combination of reduced sensation and poor circulation can spell major trouble. While these two factors tend to play the largest role in the development of foot complications, other factors can also increase the level of risk, including foot deformities, loss of eyesight, kidney disease, chronic or frequent high blood glucose, previous ulcers or amputation, and cigarette smoking.
There is good news, however. Through early identification, diagnosis, and treatment of potential problems, the vast majority of foot-related complications can be avoided. The best way to accomplish this is through an annual comprehensive foot examination, as recommended by the American Diabetes Association. This article describes what to expect during such a foot exam, and what its results may indicate in terms of further examinations and treatments.
A diabetic foot exam should be conducted by someone experienced in the procedure, who may be either a doctor or another medical professional. The examiner should ask several questions on behalf of your feet; these questions guide the procedure, and are outlined below.
What have I been through?
Your medical history is important when it comes to evaluating your risk of foot complications. Any previous ailments or medical conditions should be discussed, both general and foot-specific. Key items to note include any previous ulcers or amputations and any abnormal feelings in the feet. More general risk factors such as circulation problems, impaired vision, kidney problems, previous surgeries, pain in the feet or legs, and smoking should also be discussed with the foot specialist. This information will help the examiner tailor a plan of care to your individual needs.
Am I in good shoes?
Once your socks and shoes are removed, the foot exam can begin — yet an important part of the exam involves inspecting your shoes and the effect they’re having on your feet. Your feet should be examined for any irritation that might result from a poor shoe fit, and the shape of your feet should be compared with that of your shoes. Improper shoes may be too constrictive, too small, too large, too rigid, or too worn, all of which can result in irritation that may lead to a blister and possibly an ulcer.
Is my skin tough enough?
The examiner should proceed to inspect the surface of your entire foot: the heel, the bottom of the foot, the top of the foot, between the toes, and the nails. Important things to notice include any breaks or cracks in the skin, especially between the toes. Such cracks can act as entry points for bacteria and lead to infections. Areas of redness may indicate infection or pressure from a poorly fitting shoe. Typically, the temperature of both feet should be about the same, with maybe a degree difference here and there. If an area on one foot has a higher temperature than the same area on the other foot, this could be an indication of skin breakdown or infection.
Callused areas of the foot can be a sign of abnormal pressure, and if there is evidence of blood under a callus, this may indicate an underlying ulcer. As calluses become larger, they will typically cause pain in people who have intact sensation and may change the way they walk. For people who have lost the “gift of pain,” the pressure on these areas can be great enough to cause an ulcer underneath. It has been shown that if a callus is trimmed, this pressure can be reduced and an ulcer can often be avoided. However, check with your doctor first before attempting to trim your own callus.
The examiner should also take a good look at the toenails, with any nail polish removed. Trauma, fungus, and age can alter the way nails grow and look. Curvature of the nails toward the skin can cause them to become ingrown, which can be painful and lead to infection if not remedied. Avoiding trimming the nail corner when trimming nails can help prevent this condition.
Dry skin on the feet can be a cause for concern, both because it may indicate poor circulation and because it can lead to cracks that can become infected. Dry skin, nail problems, or extreme redness may be grounds for referral to a podiatrist or a nurse foot-care specialist.
Am I mechanically sound?
The biomechanics of feet — how they move, and what shape they are — often indicates whether future problems may be likely, as deformities can lead to pressure points and breakdown of the skin. Foot deformities can exist in several different forms, some of which require nothing but caution and accommodation — but some of which may require correction through either physical manipulation or surgery. Common deformities include bunions (in which the big toe angles toward the second toe, causing the joint at the base of the big toe to protrude), hammertoes or claw toes (which become arched in either direction), and Charcot foot (in which the foot can become red and swollen and the arch of the foot can collapse). Charcot foot, in particular, is a serious problem and in some instances can require surgery.
Sometimes calluses may indicate reduced joint mobility in an area of the foot. An example is the big toe: When a person walks, a certain amount of motion needs to occur at its main joint. If this motion is reduced for some reason such as arthritis, the body compensates by sliding the toe against the shoe or the ground. This friction can lead to callus buildup and eventually ulceration. Therefore, it may be best for a specialist to evaluate joint motion when there are calluses present on certain areas of the foot.
Am I feeling all right?
One critical part of a comprehensive foot exam is checking the sensation in the feet. People with long-standing diabetes, or those with persistently high blood glucose levels, often experience nerve damage in the legs and feet as a result. This peripheral neuropathy often causes loss of protective sensation, or reduced feeling in all or part of the feet. As many as 60% of people with diabetes will develop this complication, which is the largest single factor resulting in foot ulcers, according to several studies. There is currently no cure for numbness or loss of sensation due to neuropathy. However, being aware of reduced sensation is vital to protect the feet from injury and check for sores that might otherwise go unnoticed.
There are a number of tests that can be done to check for loss of sensation in the feet. Because these tests measure different forms of sensation, it is recommended that the examiner perform at least two during the foot exam. One test, preferred by many doctors, uses a vibration perception threshold device, or biothesiometer. This device, the use of which is painless, contains a vibrating probe that is placed on certain areas of the foot. On each area, the intensity of vibration is raised from zero volts until the person feels the vibration, or up to 50 volts. If the person does not begin to feel vibration until 25 volts or higher, this is a strong indication that the foot has lost protective sensation.
Another common test uses a 10-gram nylon monofilament, which looks a bit like a tiny piece of fishing line. The filament is pressed against certain areas of the foot until it bends, which indicates that 10 grams of force is being applied. The examiner asks whether the person feels this pressure at each site; failure to feel it may indicate loss of sensation. Other tests for loss of sensation include checking ankle reflexes, applying a vibrating tuning fork to the foot, giving non-piercing pinpricks, and alternately placing a cold then a warm object on the same area of skin to see if the person can perceive a temperature difference.
How is my circulation?
Peripheral arterial disease — which results in inadequate blood flow to the feet and legs — has been shown to significantly increase the time it takes for wounds to heal, and thus is often a factor in recurrent foot wounds. It also often leads to muscle cramping (especially in the calf) and pain while walking, symptoms you should mention to the professional examining your feet if they happen to you. Many treatments, both surgical and nonsurgical, are available for peripheral arterial disease.
The easiest way to test for adequate circulation in the feet is to check for pulses in the feet and ankles. If a pulse is felt at both locations, then adequate blood flow to the feet is likely. However, if only one location or neither one has a discernible pulse, a further test should be done. This might mean using a Doppler device to listen for pulses, or doing an ankle–brachial index test, in which a series of blood pressure cuffs are placed on the leg, as well as on one arm (the brachial artery is the major blood vessel in the upper arm). The resulting blood pressure readings are then compared; a lower reading in the leg is an indication of reduced blood flow in that area.
At the end of a comprehensive diabetic foot exam, you can expect the examiner to assign you a risk factor number of 0–3. People who fall in category 0 usually require only an annual exam. Those who fall in category 3 should have their feet examined every 1–3 months, and those in categories 2 and 3 are likely to receive instructions about monitoring their feet regularly for any changes. No matter what category you fall in, however, you should see a doctor if you notice any changes in how your foot looks or feels.
Foot problems — and, specifically, foot ulcers — are a common complication of diabetes that should be taken very seriously, since an untreated or treatment-resistant infection can severely impair mobility and eventually lead to amputation. However, the vast majority of problems can be stopped in their tracks through proper attention and medical treatment. Just as many of us have our cars serviced on a regular basis, we should also get our bodies checked out as often as is recommended. For people with diabetes, a comprehensive foot exam every year — with follow-up care as needed — can help ensure that your most important means of transportation run, or at least walk, smoothly.
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