What Is It?
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, and sometimes involves tendons, bones and other deep structures. In vulnerable people, especially those with diabetes or poor circulation, even a small foot ulcer can become infected if it is not treated quickly and efficiently. If this infection is allowed to progress, it can evolve into an abscess (a localized pocket of pus), an area of cellulitis (a deep infection of the tissue beneath the skin), osteomyelitis (bone infection) or gangrene. Among people 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 leg.
Foot ulcers are especially common in people who have one or more of the following health problems:
- Peripheral neuropathy — This is a type of nerve damage in the arms or legs in which 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 rubbing on a portion of the foot that has become numb to the sensation. People 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 shoes. They can injure their feet significantly and never know it, unless they examine their feet routinely for injury. Many elderly people and diabetics with vision problems cannot see their feet well enough to perform even this simple foot examination. This is one of the reasons that elderly people 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. People 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. People with diabetes 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 clawlike position of the toes. Diabetes also can increase the risk of fractures and dislocations of the foot bones.
More than any other group, people 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 three main risk factors: 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 eventually will 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 36 in every 100,000 people in the United States, with symptoms beginning during the late teens or early twenties.
- Raynaud’s phenomenon — 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 red again as the circulation returns to normal. Raynaud’s phenomenon tends to strike women aged 20 to 40.
Also, in 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 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 simply by looking at your foot, but this is only the beginning of the diagnostic process. If you have diabetes, your doctor will assess your 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 people susceptible to this problem. Evaluation of the ulcer includes determining:
- How deep the ulcer is
- Whether there is an infection
- Whether that infection has progressed to cellulitis (a deep skin infection) or osteomyelitis (an infection of the bone near the ulcer)
- Whether you have any underlying foot abnormalities, circulatory problems or neuropathy that will either interfere with healing or increase the risk that the ulcer will recur
Your doctor will begin by asking you to walk, because your gait may highlight knee and ankle abnormalities that can cause ulcers by distorting the distribution of pressure 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 your reflexes and use a tuning fork to see if your ability to feel vibration in the toes is normal. Your doctor also will 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, a type of Ultrasound test, 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 better define the extent of the ulcer and to determine whether it is infected, your doctor also may order blood tests, bacterial cultures of the ulcer, X-rays or other imaging tests, such as magnetic resonance imaging (MRI), Computed tomography (CT) scan or bone scan.
How long a foot ulcer lasts 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 people who have good circulation and good medical care, a superficial ulcer sometimes can heal in as few as three to six weeks. Deeper ulcers may take 12 to 20 weeks, and sometimes require surgery.
People who are at risk of foot ulcers, especially those with diabetes, probably can prevent about 50 percent of foot ulcers by examining their feet routinely and following good foot-hygiene practices. The following strategies may help prevent foot ulcers: 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, your doctor often will treat your foot ulcer by trimming away diseased tissue in a procedure called debridement. He or she also will remove any nearby callused skin. The doctor then will 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. In addition, if there is a possibility of infection, antibiotics may be recommended. Newer approaches to speed the healing of foot ulcers are under active investigation including gels containing growth factors, artificial skin, hyperbaric oxygen and a form of a medicine called phenytoin (Dilantin) that can be placed directly on the ulcer. Phenytoin currently is used in pill form to treat seizures.
Once the ulcer has healed, your doctor may prescribe special footwear to relieve pressure on vulnerable areas of your feet. This special footwear will help to prevent ulcers in the future.
Complicated foot ulcers that do not respond to more conservative therapy may require surgery. In addition, patients with poor circulation may need vascular surgery (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.
When To Call A Professional
If you have diabetes 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 people with superficial foot ulcers, the prognosis for healing is good if circulation to the foot is adequate. With the best wound-care methods available, most ulcers should heal within 12 weeks. However, about 30 percent of healed ulcers return, particularly in people who do not wear specialized footwear prescribed by their doctors.
Diseases and Conditions Center
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.