How Does Diabetes Affect Feet?
Diabetes can cause serious foot problems. These conditions include the loss of nerve function (diabetic neuropathy) and loss of circulation (peripheral vascular disease). These two conditions can lead to:
- Diabetic foot ulcers: wounds that do not heal
- Infections: skin infections (cellulitis), bone infections (osteomyelitis) and pus collections (abscesses)
- Gangrene: dead tissue resulting from complete loss of circulation
- Charcot arthropathy: fractures and dislocations that may result in severe deformities
- Amputation: partial foot, whole foot, or below-knee amputation
Symptoms of neuropathy include the loss of sensation or pain and tingling sensations. Because of the lack of sensation, patients may develop a blister, abrasion or wound, but they may not feel any pain. Decreased circulation may cause skin discoloration, skin temperature changes or pain. Depending on the specific problem, patients may notice swelling, discoloration (red, blue, gray or white skin), red streaks, increased warmth or coolness, injury with no or minimal pain, a wound with or without drainage, staining on socks, tingling pain or deformity. Patients with infection may have fever, chills, shakes, redness, drainage, loss of blood sugar control or shock (unstable blood pressure, confusion and delirium).
Neuropathy is associated with the metabolic abnormalities of diabetes. Vascular disease is present in many patients at the time of diagnosis of diabetes. Ulcers may be caused by external pressure or rubbing from a poorly fitting shoe, an injury from walking barefoot, or a foreign object in the shoe (rough seam, stone, or tack). Infections usually are caused by bacteria entering through a break in the skin such as an ulcer, area of toenail pressure, ingrown toenail or areas of skin degeneration between the bases of the toes. Gangrene may be caused by a loss of circulation.
Nerve function may be abnormal, so the patient may not feel pain. This frequently causes a delay in the diagnosis, and the patient may be diagnosed late with a limb- or life-threatening infection as a result.
The diagnosis is based on the symptoms and signs noted above. The absence of sensation may be confirmed, and images may show gas in the soft tissues, soft tissue swelling or defect, or changes consistent with bone infection, fracture or dislocation.
Ulcers are graded for size, depth and vascularity. Additional imaging studies may be helpful, including a bone scan, MRI or CT scan. Tissue cultures from the base of an ulcer may be more reliable than swab cultures from the ulcer. Vascular studies may help determine how well blood is circulating, which is important for predicting wound healing.
Wounds may be cleaned and treated with dressings and immobilization devices such as custom boots or total contact casts. Infections are cleaned and antibiotics are given. Non-surgical treatment for Charcot arthropathy may include immobilization with or without weightbearing. Gangrene of the toes may be treated with observation if the infection is under control.
Severe infections such as abscesses or osteomyelitis may be treated with surgical removal of decaying tissue or amputation. Surgical treatment for Charcot arthropathy may include correction of the deformity with operative stabilization. Vascular disease may be treated by vascular surgeons with arterial bypass procedures. Gangrene may be treated with partial foot amputation or below-knee amputation.
Close follow-up of diabetic foot patients is needed because recovery may deteriorate despite minimal warning symptoms. Prolonged recovery times are common. Ulcer healing may require several weeks or months depending on the size and location of infection, adequacy of circulation, and patient compliance. Severe infections may result in partial foot or below-knee amputation.
Risks and Complications
Non-healing ulcers lead to amputation in 84 percent of lower extremity amputations in diabetic patients. The mortality frequency of diabetic patients after a major amputation ranges from 11-41 percent by year one, 20-50 percent by year three, and 39-68 percent by year five. Infections may spread rapidly and be limb- or life-threatening.
How frequently should I examine my own feet?
Examine your feet daily and after removing shoes. If self-examination is not possible, a family member or caregiver may be trained in daily foot examination. Self-examination should include inspection for signs of pressure (redness, whiteness of skin, or other discoloration) or skin breakdown on all skin surfaces including the spaces between the toes and edges of toenails.
How frequently should my feet be examined by a health care provider?
Patients without neuropathy, vascular disease or deformity may be examined annually. Patients with neuropathy, vascular disease or deformity should be examined by a foot and ankle orthopaedic surgeon every one to two months.
How frequently should I see my surgeon if I'm being treated with a total contact cast for a foot ulcer?
After the first cast is applied, the follow-up examination is within one week. Subsequent follow-up is every one to two weeks. Any unusual symptoms should be reported to the doctor’s office immediately, including a feeling of tightness or looseness of the cast, soreness, pain, foul odor, fever, red streaks or breakdown of the cast.
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