Diabetic foot

Diabetic foot
Diabetic Foot Infection: Cellulitis and gangrene. (Image courtesy of Charlie Goldberg, M.D., UCSD School of Medicine and VA Medical Center, San Diego, CA)

Diabetic foot Microchapters
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Epidemiology and Demographics
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Diabetes mellitus Main page
Patient Information Type 1 Type 2
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Classification Diabetes mellitus type 1 Diabetes mellitus type 2 Gestational diabetes
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Afsaneh Morteza, MD-MPH [2] Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [3]; Cafer Zorkun, M.D., Ph.D. [4]

Overview

Type 2 diabetes and its complications are now considered as a growing health threat. It is the leading cause of blindness, end stage renal disease, coronary heart disease and foot ulceration which leads to amputations. In general, the incidence of nontraumatic lower extremity amputations has been reported to be at least 15 times greater in those with diabetes than with any other medical illness. Among patients with diabetes, the lifetime risk of having foot ulcer is 15%. Diabetic foot ulcers dramatically worsen the physical, psychological and social quality of life . 1 in every 4 patients with diabetes develops complications. The pathogenesis of diabetics foot is due to two causes i.e. neuropathy and vasculopathy. Due to neuropathy the patient loses sensation whereas, vasculopathy causes poor blood supply to the foot region. Due to both these contributing factors, even a small trauma to the feet can give rise to ulcer or gangrene and may even require amputation. Thus, foot examination by a podiatrist or a doctor is recommended every year.

Pathophysiology

Diabetic foot is an umbrella term for foot problems in patients with diabetes mellitus. Due to arterial abnormalities and diabetic neuropathy and delayed wound healing, infection or gangrene of the foot is relatively common. The key components of diabetic foot are neuropathy, angiopathy and trauma .

Neuropathy

The most important cause of diabetic foot is neuropathy. This is present to some extent in more than half of the patients with diabetes older than 60 years old. Peripheral neuropathy usually is profound at the point where it leads to the formation of a foot ulcer. What causes neuropathy and why it occurs is not fully known. It is most likely caused by a combination of factors such as; high blood glucose, reactive oxygen species, vasculopathy, reduced oxygenation of the nerves, inflammation, autoimmunity in diabetes, genetic factors, mechanical injury, smoking and alcohol abuse.

Generalized symmetric distal polyneuropathy is the most common and widely recognized form of diabetic neuropathy leading to diabetic foot ulcer. It may be either sensory or motor, and involves small fibers, large fibers or both. The clinical manifestations are divided into the three types of sensory, motor and autonomic neuropathy. Motor neuropathy causes wasting of small muscles of the feet with hammer toes and weakness of hands and feet.

Sensory neuropathy causes:

• Impaired vibration perception and position sense
• Depressed tendon reflexes
• Dull, crushing or cramp-like pain in the bones of the feet,
• Sensory ataxia
• Shortening of the achilles tendon
• Abnormal thresholds for warm thermal perception
• Decreased neurovascular function

Autonomic neuropathy is the increased or decreased blood flow to the foot (hot foot) with an increased risk of charcot neuroarthropathy, decreased sweating, dry skin, impaired vasomotion and blood flow. These lead to cold feet which ultimately result into the loss of skin integrity, providing a vulnerable site for infection .

Angiopathy

Micro and macrovascular complications are the leading cause of diabetic complications. Atherosclerosis occurs due to inflammation, which leads to the accumulation of foam cells. The vascular changes which are responsible for foot problems include stiff arteries due to calcification of the smooth muscle cells in the arterial wall (mediasclerosis). It is usually discovered by an impaired ankle brachial index (ABI). The resting ABI is the ratio of the blood pressure in the lower legs to the blood pressure in the arms. The ABI is calculated by dividing the systolic blood pressure at the ankle by the systolic blood pressures in the arm. It is a non-invasive method to assess the lower extremity arterial system and to detect the presence of arterial occlusion disease. In severe cases, it leads to ischemic foot problems, which the only treatment is vascular surgery. Even in neuropathic foot ulcers, the non healing wounds are the result of impaired blood supply to the tissue. Decreasing the central blood pressure by antihypertensive drugs may be deleterious for these patients. Microvascular complications cause skin damage, infection and impaired wound healing. Once a foot ulcer develops, peripheral vascular disease is the most important factor which may contribute to adverse outcomes.Vascular complications are like a positive feedback which worsen the skin and nerve damage in diabetes

Trauma

Trauma is frequently the trigger of foot ulcer as repetitive trauma and pressure to the area prevent healing. Excessive plantar pressure is related to limited joint mobility and to foot deformities (Charcot foot, hammer toe). Limited joint mobility and abnormal foot biomechanisms have been associated with an increased risk of ulceration. It could also be the result of poor vision and sensory neuropathy so that the patients does not feel the pain, nor do they see the ulcer. Loss of balance can also make patients more susceptible to falls. .

Epidemiology and Demographics

Incidence

It has been reported that annually, about 1 to 4 percent of those with diabetes develop a foot ulcer; 10 to 15 percent of those with diabetes will have at least one foot ulcer during their lifetime

Gender

In 1987, Borch-Johnsen et al. described a male preponderance for the development of severe microvascular complications . Diabetic foot disease is not an exception to this rule. For unknown reasons , men have a higher risk of diabetic foot disease compared to women. Some possible explanations are a higher bioavailability of nitric oxide (NO) bioavailability and NO responsiveness and the protective role of estrogen in women . However the beneficial effect of these factors are reversed by diabetes, irrespective of menopausal status.Nevertheless men still have a higher risk for having diabetic foot disease .

Complications

Patients with diabetic foot have an increased risk of all-cause mortality, especially cardiovascular disorders, compared with patients with diabetes without a history of diabetic foot ulcer.

Diagnosis and Evaluation

A complete physical examination and patient history is the first step. it include dermatologic, vascular, neurologic and bone examination.

Dermatologic Examination

• Visual inspection of the skin: peeling skin, maceration, fissuring between toes
• Skin temperature: Should be warm at the tibia cold at distal toe .
• Look for deformities, charcot foot, hammer toe, and heels.

Vascular Assessment

Pulses: Bilaterally, dorsalis pedis, posterior tibialis, popliteal and superficial femoral. ABI measurement:

• Normal 1-1.3
• Non compressible calcified >1.3
• Stenosis <0.9
• Advanced ischemia <0.4

Arterial oxygen supply could also be measured by transcutaneous oxymetery

Neuropathy Assessment

Symptoms including burning, pin, needles, at early stages

Using neuropathy symptoms score (NSS) and neuropathy disability score (NDS),. Almost half of the patients with diabetes have some level of neuropathy prior to diagnosis. the physician should assess;

• Muscle strength and tone
• Temperature
• Sensation
• Light touch
• Filament nerve conduction studies
• Quantitative sensory testing and autonomic testing.

Diabetic Foot Physical Examination

Inspection

• Dilated veins
• Scar, Sinuses
• Shiny skin
• Hair distribution
• Areas of Pigmentation
• Areas of discolouration
• Varicose vein
• Ulcers
• Brittle or broken nail
• Fungal infection

Palpation

• Temperature (increase temperature- deep vein thrombosis, decrease temperature-ischemia)
• Tenderness (squeeze calf muscle and achilles tendon for tenderness)
• Pulsation- Dorsalis pedis
• Capillary filling time
• Ulcers in pressure areas like ball of great toe, base of fifth metatarsal, posterior aspect of heel

Motor Examination

• Nutrition/Bulk
• Tone
• Power
• Reflexes

Sensory

• Vibration
• Joint position sense

Video: Physical Examination Diabetes

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Video: Diabetic Foot Care

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Image: Diabetic Foot Ulcer

Diabetic foot ulcer

Treatment

Foot ulcers in diabetes require multidisciplinary assessment, usually by diabetes specialists and surgeons. Treatment consists of appropriate bandages, antibiotics (against staphylococcus, streptococcus and anaerobe strains), debridement and arterial revascularisation. It is often 500 mg to 1000 mg of flucloxacillin, 1 g of amoxicillin and also metronidazole to tackle the putrid smelling bacteria. Specialists are investigating the role of nitric oxide in diabetic wound healing. Nitric oxide is a powerful vasodilator, which helps to bring nutrients to the oxygen deficient wound beds. Specialists are using forms of light therapy such as LLLT to treat diabetic ulcers.

Prevention

Foot ulcers can be prevented by is by frequent physical examinations, good foot hygiene, diabetic socks and shoes, and by avoiding injury.

• Foot-care education combined with increased surveillance can reduce the incidence of serious foot lesions .

• Footwear; all major reviews recommend special footwear for patients with a prior ulcer or with foot deformities. One review added neuropathy as an indication for special footwear. The comparison of custom shoes versus well-chosen and well-fitted athletic shoes is not clear.

Clinical Trials

Clinical Evidence reviewed the topic and concluded "Individuals with significant foot deformities should be considered for referral and assessment for customized shoes that can accommodate the altered foot anatomy. In the absence of significant deformities, high quality well fitting non-prescription footwear seems to be a reasonable option" .

National Institute for Health and Clinical Excellence has reviewed the topic and concluded that for patients at "high risk of foot ulcers (neuropathy or absent pulses plus deformity or skin changes or previous ulcer" that "specialist footwear and insoles" should be provided

A meta-analysis by the Cochrane Collaboration concluded that "there is very limited evidence of the effectiveness of therapeutic shoes" . However, the meta-analysis was published before the major trial that is in the table below.

The major randomized controlled trial of specialized footwear show no benefit in patients with a prior foot ulceration (see table below). A prior, smaller, non-randomized trial that showed benefit of custom foot wear in patients with a prior foot ulceration.. In this trial, the number needed to treat was 4 patients.

Randomized controlled trials of interventions to prevent complications of diabetic foot.

Trial	Patients	Intervention	Comparison	Outcome	Results		Comment
					Intervention	Control
Litzelman 1993	395 patients • general medicine practice	Patient and provider education	Usual care	• Any foot lesion • Serious foot lesions at one year	Not reported	• 11% • 2.9%	• Insignificant • Significant reduction
Lincoln 2008	172 patients • Prior ulceration • specialist clinic	Targeted, one-to-one education	Usual care	Re-ulceration at • 1 year 2 years	• 30% • 41%	• 20% • 41%	• Insignificant • Insignificant
McCabe 1998	2002 patients • high-risk • general diabetic clinic	Screening and referral to foot-care clinic if they had prior ulcer, had low ankle–brachial index (<0.75), or had foot deformities	Usual care	• Ulceration within 2 years • Amputation rates	• 2% • 0.1%	4% 1.2%	• Insignificant • Significant
Reiber 2002	400 patients • Prior ulceration • Excluded severe deformity	Therapeutic shoes	Usual footwear	Re-ulceration	15%	17%	Insignificant difference

External Links

• Diabetic Foot Research Page at the Center for Lower Extremity Ambulatory Research; for Professionals and Patients
• Imaging of the Diabetic Foot and Its Complications
• Assessing The Potential of Nitric Oxide in the Diabetic Foot
• Maggot Therapy Project