Research articles, most published since 1990, were identified and retrieved through computerized searches of the National Library of Medicine database (MEDLINE). This review is not meant to summarize the entire literature on the subject, but rather to present a condensation and consolidation of the major findings concerned with prevention of and early intervention for diabetes foot disease. Key points are highlighted in boldface.
2. The Scope of the Problem
National Goals for Diabetes Foot Care
The U.S. Department of Health and Human Services' report specifying health objectives for the nation, Healthy People 2000, calls for a 40 percent overall reduction in lower extremity amputations (LEA) due to diabetes by the year 2000. A special population target goal for amputations is to reduce the 1984-87 rate of amputations in African Americans from 10.2 to 6.1 per 1,000 by the year 20001. These goals are based on the estimate that at least 50 percent of the amputations that occur each year in people with diabetes can be prevented through proper foot care. To achieve the targeted 40 percent reduction, at least 80 percent of people with diabetes at high risk for lower extremity amputations must receive effective clinical management and foot care1. Current data indicate that on average, 50 to 60 percent of patients with diabetes have a semi-annual foot examination2,3.
Minorities at Higher Risk for Amputation
Analysis of a statewide California hospital discharge database indicated that in 1991, the age-adjusted incidence of diabetes-related lower extremity amputations per 10,000 people with diabetes was 95.3 in African Americans, 56.0 in non-Hispanic whites, and 44.4 in Hispanics. Amputations were 1.72 and 2.17 times more likely in African Americans compared with non-Hispanic whites and Hispanics, respectively. Hispanics had a higher proportion of amputations (82.7 percent) associated with diabetes as opposed to other causes of amputation, than did African Americans (61.6 percent) or non-Hispanic whites (56.8 percent)4.
Amputation rates in San Antonio, TX, were 66.5 per 10,000 for whites, 120.1 per 10,000 for Mexican Americans, and 181.2 per 10,000 for African Americans5. The incidence of amputations for Native Americans living on the Gila River Indian Reservation was 24.1 per 1,000 person-years compared to 6.5 per 1,000 person-years for the overall U.S. population with diabetes6. Increased awareness and identification of diabetes-related foot disease is especially important in these high-risk minority groups.
Frequency of Foot Examinations
Examination of the feet by people with diabetes and health care providers is the most basic preventive action to be taken. In the 1989 National Health Interview Survey (NHIS), 52 percent of all people with diabetes stated that they checked their feet at least daily, but 22 percent stated that they never checked their feet. More self-exams were reported by insulin treated individuals that those who did not use insulin3.
The NHIS also provided information on the frequency of foot examinations made by health professionals. Almost 53 percent of patients with diabetes reported no foot exam by a health professional within the past six months. The frequency of having no foot exam was highest in patients not using insulin (59 percent)3. In a nationwide survey, primary care physicians reported performing semi-annual foot examinations for 66 percent of patients with type 1 diabetes and for 52 percent of patients with type 2 diabetes2. A 1992 review of Indian Health Service medical records showed that close to 50 percent of patients with diabetes had documentation of an annual foot examination7.
Personal and Financial Costs
Diabetes foot disease is a major burden for both the individual and the health care system and may increase as the population ages. Fifteen percent of all patients with diabetes in a population-based study experienced ulcers or sores on the foot or ankle. The prevalence increased with age, especially in patients who were age 30 or under at diagnosis of diabetes8.
Foot disease is the most common complication of diabetes leading to hospitalization. In 1995, foot disease accounted for 6 percent of hospital discharges listing diabetes and lower extremity ulcers, with an average hospital stay of 14.7 days. Cost of care estimates for lower limb amputations in 1992 ranged from $24,000 to $27,000 and from $14,500 to $21,500 for rehabilitation. The average length of hospital stay for these two diagnoses ranged from 18.4 to 20.3 and 16.0 to 23.9 days, respectively3. The total annual cost associated with diabetes foot disease is estimated to be more than $1 billion. This cost does not include surgeons' fees, rehabilitation costs, prostheses, time lost from work, and disability payments9.
After an amputation, the chance of another amputation of the same extremity or of the opposite extremity within 5 years is as high as 50 percent. The 5-year mortality rate after lower extremity amputation ranges from 39 to 68 percent3.
3. Causative Factors
Risk Factors for Lower Extremity Amputation (LEA)
Peripheral neuropathy, peripheral vascular disease, and prior foot ulcer are independently associated with risk of LEA 10. A 1996 study of Pima Indians with diabetes confirmed this finding and included the presence of foot deformity as another independent risk factor11. The presence of plantar callus also is highly predictive of subsequent ulceration in patients with diabetic neuropathy and is more predictive of ulceration than increased plantar foot pressures12. Hyperglycemia is an additional risk factor. In a 1996 study, Finnish researchers determined risk factors for amputation in 1,044 middle-aged patients with type 2 diabetes who were followed for up to 7 years. Because the incidence of amputation was similar in both sexes (5.6 percent men and 5.3 percent women), all statistical analyses were carried out combining men and women. This study found that high fasting plasma glucose levels at baseline, high HbA1c, and the duration of diabetes were independently associated with a twofold risk of amputation. Signs of peripheral neuropathy, bilateral absence of vibration sense, and bilateral absence of Achilles tendon reflexes were two times more frequent in patients with amputation than in patients without amputation13.
These findings are supported by the Diabetes Control and Complications Trial (DCCT), a ten-year clinical study that concluded in 1993. The DCCT demonstrated that keeping blood glucose levels as close to normal as possible slows significantly the onset and progression of eye, kidney, and nerve diseases caused by diabetes. The study showed that any sustained lowering of blood glucose helps, even if the person has a history of poor control14.
Causal Pathways for Lower Extremity Amputations (LEA)
A study conducted at the Seattle Veterans Affairs Medical Center examined the causal pathways for LEA in patients with diabetes and identified the most common sequences of events. Seventy-three percent of the amputations in study subjects were a result of the causal sequence of minor trauma, cutaneous ulceration, and wound-healing failure. Estimates of the cumulative proportions of various causes indicated that 86 percent of amputations were attributed to initial minor trauma causing tissue injury15.
Precipitating or Pivotal Events
In the causal pathway study noted above, foot trauma was caused by shoe-related repetitive pressure leading to cutaneous ulceration in 36 percent of all cases, accidental cuts or wounds in 8 percent, thermal trauma (frostbite or burns) in 8 percent, and decubitus ulceration in 8 percent15. Similarly, another study found that in one-third of diabetic amputees with peripheral arterial disease, the initial lesion was self-induced. The most common cause of self-injury was ill-fitting new shoes; the second most common cause was cutting toenails improperly16. Other investigators identified external precipitating factors in 84 percent of study patients with foot ulcers. The most common factors were ill-fitting shoes/socks, acute mechanical trauma, stress ulcer, and paronychia17.
4. Screening for Patients at Risk
Screening Tools to Identify High-Risk Feet
The importance of identifying individuals at risk for foot ulceration and LEA and the need for preventive foot care practices for both the provider and the patient have been noted18. Several simple screening tools have been developed to identify people at high risk. These tools include a patient report and a clinical examination to quantify loss of peripheral sensation, foot deformities, peripheral vascular disease, and prior foot ulcers. Use of these measures has been shown to predict subsequent ulceration and amputation19.
In one study, during annual patient examinations, researchers recorded the presence of a foot deformity, history of lower extremity ulceration or amputation, and the ability to perceive the Semmes-Weinstein 5.07 10-gram monofilament at eight sites on the plantar surface of each foot. Based on the findings, subjects were classified as sensate or insensate and placed in one of four risk categories. Insensitivity to the monofilament occurred in 68 (19 percent) of the patients screened. Over a 32-month follow-up period, 41 of these patients developed ulcerations and 14 amputations occurred19.
Identifying patients' risk category for foot ulceration helps to determine the frequency needed for provider foot examinations, the level of emphasis on self-care of the feet, and patient responsibilities20.
5. Provider and Patient Education
Education Reduces Lower Extremity Abnormalities
In a randomized, controlled study, researchers provided intervention patients with foot care education, behavioral contracts, and telephone and postcard prompts. The researchers placed foot care prompts on the medical record, and provided practice guidelines and flow sheets to clinicians assigned to those patients. Results showed that primary care physicians in the intervention group conducted more examinations of lower extremities, identified those at risk for amputation, and referred more patients for podiatric care. Patients in the intervention group received more patient education, made more changes in appropriate self-care behaviors, and had fewer short-term foot problems than patients in the control group21.
The Components of Good Patient Education
Findings from several studies help determine effective components of patient education that contribute to successful patient outcomes. These include giving detailed foot care recommendations, requesting patient commitment to self-care, demonstrating and practicing foot care procedures, and communicating a persistent message that foot complications can be avoided by self-care. In comparing the effectiveness of intensive versus conventional education, researchers found that patients in the intensive group showed greater improvement in foot care knowledge, better compliance with the recommended foot care routine, and greater reduction in the number of foot problems requiring treatment22.
Foot care recommendations and demonstrations should include: washing, drying, and inspecting the feet; cutting toenails; treating minor foot problems; selecting suitable footwear; dealing with temperature extremes; and contacting the physician if problems do not resolve quickly. Patients with high-risk feet should inspect them twice a day. Those with peripheral neuropathy, vascular disease, or eye disease should not attempt to cut their own toe nails as this can lead to serious self-inflicted injury. It is important for the provider or diabetes educator to review with the patient all written take-home instructions for self-care of the feet20.
Researchers found that the frequency of desired self-care behaviors improved when patients were given specific instructions such as "dry between toes" and "file calluses" rather than more general instructions such as "avoid injury to your feet." To be more effective, the investigators recommended that instructions should be stated as precisely as possible such as "don't go barefoot indoors21."
Patients should never be allowed to walk on open plantar ulcers since continuous application of mechanical load will prevent healing. Walking aids, footwear modifications, or other interventions must be used to relieve weight23.
A pilot program for African Americans consisted of a 15-minute orientation meeting between a diabetes nurse educator and the person with diabetes, a take-home foot self-care packet, and a follow-up telephone interview. During the telephone interviews, subjects reported that the most useful parts of the take-home packet were the patient instruction booklet, the large hand mirror included in the packet, and the foot care knowledge self-test with explanations of the answers. Subjects also valued the reminder cue that was repeated in bold face on each page of the booklet telling them to call the doctor immediately if any cut, bruise, or blister does not begin to heal after one day24.
Step-by-step guidelines have been published to assist providers to conduct patient education workshops on foot care including how to attract participants, promote the workshop, develop the agenda, identify appropriate speakers, and conduct a post-workshop evaluation25.
6. Clinical Issues
Provider Foot Care Practices
In a study of provider practice, researchers found that clinicians were likely to prescribe preventive foot care behaviors when they were aware of a patient's high risk for LEA as evidenced by prior history of foot ulcer. Clinician awareness of two other risk factors (peripheral neuropathy or peripheral vascular disease), however, did not increase preventive care practices. The researchers concluded that physicians and patients need periodic reminders to identify patients in all high-risk categories for ulcer or amputation and to provide additional care such as podiatric visits and education in self-care10.
A study of nurse practitioner practice patterns was conducted to determine their consistency with the American Diabetes Association (ADA) standards of care. An audit of 78 medical records representing a proportionate number for each of six masters-prepared, certified nurse practitioners revealed discrepancies between established standards and the degree to which they were documented. Comprehensive foot care examinations (required annually by ADA standards) were documented in 23 percent of the charts reviewed26.
Self-care Limitations in the Elderly
In one study, barriers to carrying out daily foot care noted by elderly subjects included lack of motivation, forgetfulness, vision problems, joint and knee problems, and family responsibilities24. The ability of elderly people to identify foot lesions was investigated further in a matched comparison, controlled study. Findings showed that 43 percent of patients with a history of foot ulcers could not reach and remove simulated lesions on their toes; over 50 percent of the older subjects reported difficulty trimming their toe nails; and only 14 percent had sufficient joint flexibility to allow inspection of the plantar aspect of the foot. The investigators concluded that elderly people who are unable to perform daily self-care of the feet would benefit more from regular foot care given by others than from intensive education27.
In people with diabetes, regular exercise can lower blood glucose, improve insulin sensitivity, raise HDL cholesterol, improve blood flow and heart muscle strength, enhance fibrinolysis, control weight, increase muscle mass, and provide an overall sense of well-being. Because of these effects, regular exercise may also delay the onset of neuropathy and atherosclerosis.
People who have had type 1 diabetes for more than 10 years, or type 2 diabetes for more than 5 years, should be screened for medical risk prior to beginning an exercise program. While the presence of neuropathy does not rule out exercise, care should be taken not to worsen soft tissue and joint injury or cause foot ulcers or bone injury. Stretching muscles before exercise is important to prevent ligament strain. Swimming or bicycling are recommended forms of exercise because they avoid abrasion to the feet28. Attention to the construction and fit of footwear is essential.
7. Special Footwear for the Insensate Foot
Repetitive Stress and Special Footwear
People with intact sensation respond to repetitive stress that occurs during walking either by shifting the pressure to another part of the foot, by modifying the way the foot meets the ground, by resting, or by checking their shoes for problems. With the loss of peripheral sensation, however, many people with diabetes have no indication of lower extremity pain, pressure, or trauma and do not take measures to modify repetitive pressures. Lack of feeling makes shoe-fitting assistance essential.
Properly constructed and well-fitting shoes and shoe inserts can minimize localized stresses by redistributing forces during walking. Besides helping patients keep feet healthy, shoes and orthoses also can help prevent diabetes complications. Investigators in a recent study found that after healing of the initial ulcer, re-ulceration occurred after one year in 58 percent of patients who resumed wearing their own footwear, compared to 28 percent of those who wore therapeutic footwear29.
Another study compared the prevalence and severity of foot deformities and the development of ulceration in people with diabetes after a great toe amputation. The investigators found that because of altered pressure distribution, the foot with great toe amputation developed more frequent and more severe deformities of the lesser toes and metatarsophalangeal joints compared to the other intact foot. Because these patients were at high risk for subsequent ulceration, the use of special inserts and footwear to protect the feet was highly recommended30.
Prescription Footwear and the Medicare Shoe Benefit
Professionally fitted shoes and prescription footwear are an important part of the overall treatment of the insensate foot because they aid in preventing limb loss. Footwear should relieve areas of excessive pressure, reduce shock and shear, and accommodate, stabilize, and support deformities.
Shoes should be long enough, and have room in the toe area and over the instep. Shoes with laces allow adjustment for edema and deformities. Most people with early neuropathic changes can wear cushioned commercial footwear such as walking or athletic shoes. Some people also may need the pressure areas redistributed with custom orthotics that often require depth footwear.
Custom-molded shoes, depth shoes, inserts, and shoe modifications can be fitted and furnished by a podiatrist, orthopedic foot surgeon, orthotist, or pedorthist. Depth-inlay shoes provide more room for toe deformities and for the insertion of customized insoles. Extra-wide shoes provide more room for bunions and other abnormalities. Rocker sole shoes reduce pressure under metatarsal heads and toes. They are particularly useful for reducing the risk of ulceration in patients with a stiff and rigid first metatarsal joint.
Since 1993, the Medicare shoe benefit has made special footwear available to more patients than ever before. To obtain coverage, patients must have physician certification that they are at high risk for ulceration or amputation, receive a written footwear prescription from a podiatrist or other qualified physician, and obtain the footwear from a qualified provider or supplier who will then file the appropriate claim forms31.
The staggering human and economic costs of diabetes foot disease may be reduced significantly with increased practice of several simple preventive care measures designed to prevent foot ulcers and lower extremity amputations. Routine annual foot screening facilitates early interventions to reduce the incidence of the most common precipitating events including injury and footwear-related trauma to the insensitive foot. The key elements of preventive care include: annual examination of the feet by health care providers to determine risk factors for ulceration; subsequent exams of high risk feet at each patient visit; patient education about daily self-care of the feet; and careful glucose management. The national health objectives for the year 2000 to decrease the rate of amputation in the population overall, as well as in specific high risk minority groups, serve as a call to action for both health care providers and people with diabetes to make routine diabetes foot care a high priority.
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