Abstract
As the rate of patients developing diabetes and prediabetes increases, the risk of developing ulcerations leading to amputation increases. The incidence of open wounds in patients with diabetes is very high and affects 1 of every 6 patients. These nonhealing "diabetic ulcers" are the major cause of leg, foot, and toe amputations. The ulcers do not occur spontaneously but are always preceded by a gradual or sudden injury to the skin by some external factor. Preventing these types of injuries, and early recognition when they do occur, can reduce the risk of the wound progressing to the point of amputation. Healthcare providers play an important role in recognizing the early signs of changes in the feet. Early patient education has been proven to be beneficial in identifying these changes that are brought about as a result of diabetes and, by doing so, reducing the risk of complications. This article reviews the typical changes that may occur in the feet of patients with diabetes and discusses how early recognition and prevention can assist in reducing the complications that occur as a result of ulcerations.
Article Content
PREVALENCE AND RISK FACTORS
More than 5 million people in the United States are at risk for diabetes-related problems. People with diabetes spend more time in the hospital for treatment of foot problems related to diabetes than for any other reason. Approximately 15% of individuals with diabetes have had an ulcer on the foot or ankle. Diabetes is estimated to be the primary causative factor in 45% of all lower extremity amputations, with 60% of nontraumatic amputations being the result of long-term complications of diabetes. This percentage increases the longer one has had diabetes.1,2 In one Health Maintenance Organization review, 5.8% of all patients with diabetes had neuropathic ulcerations, with 15% developing osteomyelitis. The 3-year survival rate of those developing the ulcerations was 13% less than for those without ulcers.3 In 2000, the age-adjusted rate of lower extremity amputations among American Indians was found to be 3.5 times higher than the non-Hispanic white population.4 The incidence of lower extremity amputation was also twice as high for men as for women and increased with age.4 Amputation is found to be a much higher cost to the health system because of the multiple and prolonged hospitalization than the lower cost of prevention or the multidisciplinary approach to care of patients with diabetes and related ulcers.5,6 A study by Al-Tawfiq and Johndrow in Saudi Arabia concluded that
Patients with diabetic foot ulcers require aggressive management to reduce morbidity and mortality associated with major amputations in patients with diabetes...and preventative measures for developing diabetic foot ulcers are needed for those patients identified to be at high risk for foot ulcerations.
Neuropathy is the greatest risk factor for ulceration in patients with diabetes.8,9 There are several types of neuropathy that lead to structural and pathological changes of the foot, resulting in an increased risk for ulceration and amputation. Early recognition of the symptoms of neuropathy is important because these may precede the onset of blood glucose abnormalities. These include sensory, motor, and autonomic neuropathies. Sensory neuropathy is seen as impaired sensation in the hands and feet. Nearly 50% of all persons with diabetes have lost the ability to feel pain, heat, or cold and the sense of touch. The patient may complain of paresthesias in a stocking-like distribution and/or superficial or deep shooting pain. There is a loss of vibration sense, proprioception, light touch, and eventually a loss of pain sensation. This leads to a totally insensitive foot and can progress to neuropathic arthropathy (Charcot foot). Motor neuropathy changes include muscle weakness and wasting of the intrinsic muscles of the foot. With a flexor-extensor muscle imbalance, there is a dorsal subluxation of the digits. This change in structure results in abnormal weight bearing on the metatarsal heads, which leads to ulcerations. Autonomic neuropathy changes are seen as decreased perspiration, dryness and fissuring of the skin, and a loss of microcirculation.10 Eighty percent of those with a diagnosis of diabetes have some form of neuropathy and often a combination of several types of neuropathy. Severe forms of neuropathy are the major contributing cause of lower extremity ulcerations and amputations.11 The more accurate term for these neuropathic ulcerations is mal perforans ulcer.
EFFECT OF DIABETES ON THE FEET
People with diabetes experience higher than normal blood glucoses as well as damage to small blood vessels, which can result in damage to the nerves in the foot and leg, decreasing the ability to feel injuries. The motor nerves that control the shape of the foot are also damaged, resulting in deformities of the bony prominences such as the interphalangeal joints, tips of the toes, heel, and the arch and ball of the foot. These bony prominences may be continually rubbed or pressed by shoes causing skin injuries through mechanical forces. The elevated blood glucose levels can impair the circulation of the blood vessels that supply the skin.12 When there is a skin injury, the body requires 50 times the normal blood flow to heal. When the circulation is already impaired as a result of the elevated blood glucose levels, the resultant blood flow required for healing is unavailable, so the skin injury will deteriorate resulting in a worsening of the wound and increasing the risk of a rapid onset of infection.
FOOT CHANGES
Structural
Along with the nerve damage that can change the shape of the feet and toes, muscle atrophy can occur resulting in biomechanical changes leading to abnormalities in gait and balance. Injuries can occur as a result of these structural changes. Common structural changes include pes equinas, hallux limitus/rigidus, hallux valgus, hammer toes, varus deformities of the toes, and tailor's bunion on the fifth metatarsal. A series of fractures to the bones, ankle equinas, decreased sensation, and increased blood flow to the bone can result in demineralized bone leading to a Charcot foot deformity (Fig 1). Utilizing the Fiess line (a line between the inner apex of the medial malleolus and the head of the first metatarsal) and the relationship between the navicular and this line when the patient is in a weight-bearing position, the structure of the patient's arch can be determined. This can be documented evidence of progression toward pes planus and need for supportive intervention.
The structural changes that occur with diabetes can affect mobility and balance. A thorough evaluation of gait, balance, and strength through appropriately chosen functional outcome tests will enable the therapist to design appropriate interventions for patients to decrease their fall risk.
Nails/skin
The nerves that control the oil and moisture to the foot become impaired with diabetes. The result is dry skin that may peel and crack. The resultant fissures of dry skin are portals to infections.13 Skin can become drier with repeated soaking of the feet. Patients should be instructed to avoid soaking the feet and to utilize unscented moisturizers or petroleum jelly applied thinly to the feet but not between toes. Moisturizers between toes can lead to infection.
Calluses build up more often on the feet of people with diabetes. This is the result of high-pressure areas under the foot as the structure and biomechanics change. Calluses indicate the need for proper fitting shoes with pressure relief. Too often, patients continue to buy the same size shoes year after year, even though their feet are changing. This puts them at risk for developing calluses. Calluses can get thick, break down, and turn into ulcers if not properly trimmed by a healthcare professional
Patients should be instructed to never trim their own callus. They can be taught to properly use a pumice stone after bathing.
Sensory
Many sensory changes occur as a result of nerve damage. Patients may complain of paresthesia, describing the sensation as spiders crawling, burning, or electrical charges. Test and measures for the evaluation of sensory changes include a vibration test with a tuning fork. A 128-Hz tuning fork is placed on the great toe, medial malleoli, and tibial tuberosity, with the patient answering yes or no to when he or she feels the vibration and when the sensation stops. Another test is for proprioception, the up-and-down test on the great toe. The most important sensory test for neuropathic ulcers is the testing of protective sensation through the Semmes Weinstein monofilament test (Fig 3). This test is performed by utilizing a 10-g (or 5.07) filament and testing 10 points on the foot: plantar surface of digits 1, 3, and 5; metatarsal heads of digits 1, 3, and 5; medial and lateral arches; heel; and the dorsum of the foot. The score is determined by the number of times the patient did not feel the sensation. An inability to feel any 3 of the sites constitutes a positive test for a foot at risk for ulcerations. These sensory tests identify areas of concern for education on daily foot examinations.
The Centers for Disease Control and Prevention has determined that "regular foot care can reduce serious foot disease by 50-60% affecting the quality of life of our aging population, and potential benefits to the Medicare/Medicaid programs could be profound."2 Increasing the proportion of persons with diabetes who receive preventive foot care and reducing lower extremity amputations in the United States were included in the national health objectives for 2010.15 From 1995 to 2001, the prevalence of annual foot examinations among those with diabetes increased from 56% to 62.3% but was still under the national target of 75%.1 Many studies have looked at the financial implications of preventive foot care. There is overwhelm