People who have diabetes mellitus should be very concerned about their feet. The most common complications of diabetes are from damage to the eyes, kidney and the feet. Almost everyone knows someone who has had a disastrous complication of the foot because of diabetes. While diabetes is the most common disease resulting in amputation, amputation is actually fairly rare when considering the number of people with diabetes. Careful foot care, aggressive treatment of blood sugar levels, and smoking cessation will usually help prevent this.
The increased sugar concentration in the blood of people with diabetes damages nerves. The longest nerves are damaged first and these happen to be the ones to the foot. The result is numbness, changes in circulation, muscle weakness, skin rashes and stiffness of the toes.
There are two reasons that the nerves are damaged. First, glucose can actually attach to the all proteins in the body including those that are in nerves. Most proteins in the body have a limited lifespan. They are continually produced and broken down. The proteins that do not turn over rapidly or are made of certain reactive amino acids can have enough glucose attached to them to impair their function. Proteins in the nerve membranes that control the electrical impulses of the nerves seem to be prone to this damage. Second, the increased glucose concentration promotes the production of certain toxins within the nerve cells that hamper their ability to generate energy.
Diabetes can also accelerate hardening of the arteries or arteriosclerosis. This causes the arterial circulation of the foot to decrease, eventually starving the foot of food and oxygen. When the loss of circulation is combined with the numbness, the foot becomes prone to injury and these injuries are much more difficult to coax into healing. Problems that occur in people with diabetes include painful neuropathy, stress injuries, ulceration, and infection.
Painful neuropathy or pain from the sick nerves is generally perceived as burning, aching, or a tight feeling in the feet. It is often more intense at night and can be severe enough to require medication. Initially, anti-inflammatory medications such as naproxen (Aleve) and ibuprofen (Advil, Motrin) and other over-the-counter pain medications such as acetaminophen (Tylenol) can help these symptoms. Lotions such as capsaicin (Zostrix) can also be applied and give relief. When beginning treatment with this lotion, burning is often noted, but generally resolves with the first few days of application. Other prescription medication such as gabapentin (Neurontin), duloxetine (Cymbalta), pregabalin (Lyrica) and topiramate (Topamax) are also effective in more severe cases, but have more side effects. Perhaps the most effective method of addressing these symptoms is careful control of the diabetes through effective medication and monitoring serum glucose level at home with the help of your primary care physician.
Stress injuries, otherwise known as diabetic arthropathy or Charcot arthropathy, are sometimes sustained by people with diabetic nerve damage. The initial symptoms are unusual swelling, redness, and pain. It is often confused with infection. A simple “sprain” is not simple in someone with diabetes. If you experience any of these symptoms, an orthopedist, podiatrist, or other physician should evaluate you immediately. This injury can lead to foot deformities so severe that they require surgery, because the deformity may make wearing normal shoes impossible without injuring the foot. The treatment is protection, immobilization, and/or prolonged restriction of weight bearing using cast, crutches or a walker for as long as six months. Surgery is occasionally necessary.
Ulceration is caused by repetitive or prolonged pressure on a portion of the skin. The pressure can impair the circulation until it the skin dies. Often pressure from a bone underneath the skin combined with age-related thinning of the protective skin causes it, but prolonged pressure to the back of the heel can also cause pressure this great just by resting the foot on a hard surface. A person with diabetic nerve damage should never elevate their leg on a table or other hard surface for a prolonged period of time or use heating pads on their feet. The break in the skin can lead to infection of the deep structures if left untreated. Early signs of a possible ulceration are a heavy callus, blue, black or purple patch (caused by bleeding underneath the skin), or a blister. If you have an ulceration or any of these other warning signs, you should be under a doctor’s supervision until the ulcer is completely healed.
-Brett Fink, MD, Indiana Orthopedic Center, Indianapolis, IN, (317) 588-2663, co-author of The Whole Foot Book, A Complete Program for Taking Care of Your Feet.