Diabetes

The diabetic foot

Motor, sensory and autonomic fibres may all be affected in people with diabetes mellitus. Because of sensory deficits, there are no protective symptoms guarding against pressure and heat and so trauma can initiate the development of a leg ulcer. Absence of pain contributes to the development of Charcot foot, which further impairs the ability to sustain pressure. Motor fibre abnormalities lead to undue physical stress, the development of further anatomical deformities (arched foot, clawing of toes), and contribute to the development of infection. When infection complicates a foot ulcer, the combination can be limb or life-threatening.

Ulcer and foot lesions

What is a foot ulcer?

A skin ulcer is where an area of skin has broken down and you can see the underlying tissue. Most skin ulcers occur on the lower legs or feet. The skin normally heals quickly if it is cut. However, in some people especially those with diabetes and poor circulation the skin on the feet does not heal so well and is prone to develop an ulcer. This can be even after a mild injury such as stepping on a small stone in your bare feet.

Why are people with diabetes prone to foot ulcers?

Because one or both of the following complications develop in some people with diabetes.

Reduced sensation of the skin on the feet

Your nerves may not work as well as normal because even a slightly high blood sugar level can, over time, damage nerves. This is a complication of diabetes called 'peripheral neuropathy of diabetes'. The nerves that take messages of sensation and pain from the feet are commonly affected. If you lose sensation in parts of your feet, you may not know if you damage your feet. For example, if you tread on something sharp, or develop a blister due to a tight shoe. Therefore, you are more prone to problems such as minor cuts, bruises, blisters. Also, if you cannot feel pain so well from the foot, you do not protect these small wounds by not walking on them. Therefore, they can quickly become worse and develop into ulcers.

Narrowing of arteries (blood vessels) going to the feet

If you have diabetes you have an increased risk of developing 'furring' of the arteries. This is caused by fatty deposits called atheroma that build up on the inside lining of arteries. This can reduce the blood flow to various parts of the body. The arteries in the legs are quite commonly affected. This can cause a reduced blood supply ('poor circulation') to the feet. Skin with a poor blood supply does not heal as well as normal and is more likely to be damaged. Therefore, if you get a minor cut or injury, it may take longer to heal and is prone to become worse and develop into an ulcer. In particular, if you also have reduced sensation and cannot feel the wound.

What increases the risk of developing foot ulcers?

• If you have reduced sensation to your feet (see above). The risk of this occurring increases:
  • the longer you have diabetes, and the older you are.
  • if your diabetes is poorly controlled. This is one of the reasons why one aim of treating diabetes is to keep the blood sugar level as near normal as possible.
• If you have narrowed arteries (see above). The risk of this occurring increases:
  • the longer you have diabetes, the older you become, and if you are male.
  • if you have any other 'risk factors' for developing 'furring of the arteries'. For example, if you smoke, do little physical activity, have a high cholesterol level, high blood pressure, or you are overweight.
• If you have had a foot ulcer in the past.
• If you have other complications of diabetes such as kidney or eye problems.
• If your feet are more prone to minor cuts, grazes, corns or calluses which can occur:
  • if you have foot problems such as bunions which put pressure on points on the feet.
  • if your shoes do not fit properly which can put pressure on your feet.
  • if you have leg problems which affect the way that you walk, or prevent you bending to care for your feet.

Are foot ulcers serious?

They can be. Foot ulcers often respond well to treatment. However, foot ulcers can get worse and can take a long time to heal if you have diabetes, particularly if your circulation is not so good. Also, because of the complications of diabetes, infection can occur. Sometimes more serious problems can develop such as gangrene. In extreme cases, the foot may need to be amputated. However, foot ulcers can often be prevented by taking care of your feet.

What can I do to help prevent foot ulcers?

As a rule, the better the control of your diabetes, the less likely you are to develop complications such as foot ulcers. Also, where appropriate, treatment of high blood pressure, high cholesterol level, and reducing any other risk factors will reduce your risk of diabetes complications. In particular, you are strongly advised to stop smoking if you smoke.

Have your feet regularly examined

Most people with diabetes are reviewed at least once a year by a doctor / podiatrist and other health professionals. Part of the check is to examine the feet to look for problems such as reduced sensation or poor circulation. If any problems are detected then more frequent feet examinations will be recommended.

Foot care

Research has shown that people with diabetes who take good care of their feet, and protect their feet from injury, are much less likely to develop foot ulcers.

• Looking carefully at your feet each day, including between the toes. If you cannot do this yourself, you should get someone else to do it for you. Looking is particularly important if you have reduced sensation in your feet, as you may not notice anything wrong at first until you look.
• If you see anything new (such as a cut, bruise, blister, redness, or bleeding) and don't know what to do, see your doctor or podiatrist (chiropodist).
• Do not try to deal with corns, calluses, verrucas, or other foot problems by yourself. They should be treated by a health professional such as a podiatrist. In particular, do not use chemicals or special 'acid' plasters to remove corns, etc.
• Use a moisturising oil or cream for dry skin to prevent cracking. But, do not apply it between the toes.
• Look out for athlete's foot (a common minor skin infection). It causes flaky skin and cracks between the toes which can be sore and can become infected. If you get athletes foot, it should be treated with an antifungal cream.
• Cut your nails by following the nail curvature rather than 'straight across'. If you cannot see properly do not try to cut your nails as you may cut your skin. Get someone else to do it.
• Wash your feet regularly, and dry carefully, especially between the toes.
• Do not walk barefoot, even at home. You might tread on something and damage the skin.
• Always wear socks with shoes or other footwear. But, don't wear socks that are too tight around the ankle which may affect the circulation.
• Shoes, trainers and other footwear should:
  • fit well to take into account any awkward shapes or deformities (such as bunions).
  • have broad fronts with plenty of room for the toes.
  • have low heels to avoid pressure on the toes.
  • have good laces, buckles or Velcro fastening to prevent movement and rubbing of feet within the shoes.
• When you buy shoes, wear the type of socks that you usually wear. Avoid slip-on shoes, shoes with pointed toes, sandals and flip-flops. Break new shoes in gradually.
• Always feel inside footwear before you put them on (to check for stones, rough edges, etc).
• If your feet are an abnormal shape, or if you have bunions or other foot problems, you may need specially fitted shoes to stop your feet rubbing.
• Tips to avoid foot burns include: check the bath temperature with your hand before stepping in; do not use hot water bottles, electric blankets or foot spas; do not sit too close to fires.

What if I develop a foot ulcer?

Tell your doctor or podiatrist straight away if you suspect an ulcer has formed. Treatment aims to dress and protect the ulcer, to prevent or treat any infection, and to help the skin to heal.

• The ulcer is usually covered with a protective dressing.
• A nurse or podiatrist will normally examine, clean and re-dress the ulcer regularly.
• A podiatrist may need to remove any hard skin that prevents the ulcer from healing. Also, depending on the site and size of the ulcer, they will protect it from further injury by using padding to take the pressure off the area.
• You may also be advised to wear special shoes or have a cast made for your foot to keep the pressure off the ulcer.
• Antibiotics will be advised if the ulcer, or nearby tissue, becomes infected.
• Sometimes a small operation is needed to drain pus and clear dead tissue if infection becomes more severe.
• In some cases the arteries in the legs are very narrow and greatly reduce the blood flow to the feet. In these cases an operation to bypass, or widen, the arteries may be advised.

Many foot ulcers will heal with the above measures. However, they can take a long time to heal.
In some cases the ulcer becomes worse, badly infected, and does not heal. Sometimes infection spreads to nearby bones or joints which can be difficult to clear, even with a long course of antibiotics. Sometimes the tissue in parts of the foot cannot survive and the only solution then is to amputate the affected part.