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Foot Ulcers
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A foot ulcer is an open sore on the foot. Some foot ulcers are superficial, producing a shallow red crater that involves only the surface skin. Other foot ulcers are very deep, producing a crater that extends through the full thickness of the skin, sometimes involving tendons, bones and other deep structures. In vulnerable individuals, especially those with diabetes or poor circulation, even a small foot ulcer may become infected if it is not treated quickly and efficiently. If this local infection is allowed to progress, it can evolve into an abscess (a localized pocket of pus), an area of cellulitis (infection of soft tissue), osteomyelitis (bone infection) or gangrene. Among persons with diabetes, a seemingly simple foot ulcer is the initial problem in approximately 85 percent of severe foot infections that ultimately require amputation of some part of the lower limb.
Foot ulcers are especially common in persons who have one or more of the following health problems:
Peripheral neuropathy — In peripheral neuropathy (nerve damage in the extremities), the nerves that normally detect sensations in the feet can no longer warn about pain or discomfort. When this happens, even tight-fitting shoes can trigger a foot ulcer by simply rubbing on a portion of the foot that has become numb to the sensation. Persons with peripheral neuropathy may not be able to "feel" it when they've stepped on something sharp or when they have an irritating pebble in their shoe. They can significantly injure their feet and never know it, unless they routinely examine their feet for sites of injury. Unfortunately, many elderly individuals and diabetics with vision problems cannot see their feet well enough to perform even this simple foot examination. This is one of the reasons why elderly individuals with peripheral neuropathy develop foot ulcers more than nine times more often than those with normal foot sensation.
Circulatory problems — Any illness that decreases circulation to the feet can cause foot ulcers by decreasing the foot's blood supply, which deprives cells of oxygen, making the skin more vulnerable to injury and slowing the foot's ability to heal. Persons are at especially high risk of foot ulcers if the circulation in their leg arteries is reduced because of atherosclerosis, a disease that is triggered by fatty deposits of cholesterol within the walls of arteries.
Abnormalities in the bones or muscles of the feet — Any condition that distorts the normal anatomy of the foot can lead to foot ulcers, especially if the foot is forced into shoes that cannot accommodate the foot's altered shape. Diabetics are at higher risk of foot abnormalities that can lead to foot ulcers. This is because long standing, poorly-controlled diabetes can cause nerve and muscle problems that can lead to claw foot (muscle contractions that produce a claw-like position of the toes) and increase the risk of fractures and dislocations of the foot bones.
More than any other group, persons with diabetes have a particularly high risk of developing foot ulcers. This is because the long-term complications of poorly-controlled diabetes often include the triple risk factors of neuropathy, circulatory problems and a gradual development of structural abnormalities in the feet. Among the estimated 16 million diabetics living in the United States, approximately 15 percent will eventually develop an ulcer involving either the foot or ankle. Without prompt and proper treatment, this ulcer may become so severe that it requires hospital treatment or even amputation.
In addition to diabetes, other medical conditions that increase the risk of foot ulcers include:
Atherosclerosis — This condition involves poor circulation to the legs.
Hereditary motor and sensory neuropathy — This inherited form of neuropathy can affect sensation and movement in the feet. This condition affects 30 in every 10,000 Australians, with symptoms beginning during the late teens or early twenties.
Raynaud's disease — This condition causes sudden episodes of decreased blood flow to the fingers and toes. During these episodes, the fingers and toes initially turn white as the blood supply diminishes, then blue, and turn red again as the circulation returns to normal. Raynaud's disease tends to strike women aged 20 to 40.
Also, in relatively rare cases, a foot ulcer may be unrelated to these risk factors and illnesses. For example, an isolated foot ulcer in a person who has no underlying health problems may potentially be a site of skin cancer, especially squamous cell carcinoma.
A foot ulcer looks like a red crater in the skin, usually located on the sole of the foot or between the toes. In many cases, this crater is surrounded by a well-defined border of thickened, callused skin, especially if it has been present on the foot for a fairly long time. In very severe ulcers, the red crater may be very deep, exposing foot tendons or bones.
If the nerves to the foot are functioning normally, then the ulcer will be painful. If not, then the patient may not know that the ulcer is there, particularly if the ulcer is located on a less-obvious portion of the foot. In debilitated or elderly patients, a relative or caregiver may first notice the problem when the ulcer becomes infected, drains pus and develops a foul odor.
In most cases, your doctor can tell that you have a foot ulcer by simply looking at your foot, but this is only the beginning of the diagnostic process. Your doctor will assess the control of your blood sugar and will ask about your routine foot care practices and the type of shoes that you usually wear. This is because poor foot hygiene and poorly-fitting shoes can increase the risk of foot ulcers in susceptible individuals. Evaluation of the ulcer includes determining:
Your doctor will begin by asking you to walk, because your gait may uncover knee and ankle abnormalities that can cause ulcers by distorting the pressure distribution on the soles of your feet. Next, your doctor will examine both of your feet for obvious structural problems, such as claw foot or fallen arches. To check for neuropathy, your doctor will test the sensation in your feet, check reflexes and use a tuning fork to see if your ability to feel vibration in the toes is normal. Your doctor will also assess the circulation in your legs and feet by feeling your pulses and noting whether your feet are pink and warm. If your pulses are diminished, then your doctor may order Doppler flow studies to assess your circulation.
Finally, your doctor will examine the ulcer itself, probing it to see how deep it is and checking for exposed tendons, bone fragments or signs of cellulitis. To help in the overall assessment, your doctor may also order bacterial cultures of the ulcer (to check for infection), blood tests and radiographic imaging of the foot.
The duration of a foot ulcer depends on the depth of the ulcer, the adequacy of blood circulation to supply oxygen and nutrients, and whether there is any secondary infection. In persons who have good circulation and good medical care, a superficial ulcer can sometimes heal in as little as five to six weeks. Deeper ulcers may take 12 to 20 weeks and sometimes require surgery.
Persons who are at risk of foot ulcers, especially those with diabetes, can probably prevent about 50 percent of foot ulcers by routinely examining their feet and following good foot hygiene practices. The following strategies may help:
- Examine every part of your feet every day. If necessary, use a mirror to check the heel and sole. If your vision is not good, ask a relative or caregiver to examine your foot for you.
- Practice good foot hygiene. Wash your feet every day using mild soap and warm water. Dry thoroughly, especially between the toes. Apply moisturizing lotion to dry areas, but not between the toes.
- Wear well-fitting shoes and soft, absorbent socks. Always check your shoes for foreign objects and rough areas before you put them on. Change your socks immediately if they become wet or sweaty.
- Trim your toenails straight across with a nail clipper or emery board.
If you have corns or calluses, ask your doctor about how to care for them. Your doctor may determine that these problems are best treated in his or her office rather than at home.
If you have good circulation in your foot, the doctor will often treat your foot ulcer with debridement (trimming away of diseased tissue), together with careful removal of any nearby callused skin. The doctor will then apply a dressing and prescribe specialized footwear to relieve pressure on the ulcerated area. This specialized footwear may be a total contact cast, a postoperative walking shoe with a special lining or a fully enclosed healing shoe. The process of debridement, callus removal and dressing changes will be repeated over a period of weeks or months — as long as it takes for your ulcer to heal completely. A "growth factor" gel containing becaplermin (Regranex) may be applied to the ulcer to speed the healing process. Once healing is done, your doctor will prescribe special footwear to relieve pressure on vulnerable areas of your feet. This special footwear will help prevent your ulcer from recurring.
Complicated foot ulcers often require antibiotics and surgery.
In addition, patients with poor circulation may need either percutaneous transluminal balloon angioplasty or an arterial bypass graft to correct blood flow problems in their leg arteries. Without these procedures, circulation to the injured foot may be too poor to allow the ulcer to heal properly.
If you are a diabetic or if you suffer from poor circulation or peripheral neuropathy, examine your feet every day. If you see an area of redness, swelling, bleeding, blisters or any other abnormality, call your doctor promptly.
In patients with superficial foot ulcers, the prognosis for healing is good if the foot's circulation is adequate. By using the best wound care methods available, most ulcers should heal within 12 weeks. Unfortunately, about 30 percent of healed ulcers recur, particularly in patients who do not wear specialized footwear prescribed by their doctor.