1
Introduction

N. Tentolouris

First Department of Propaedeutic Internal Medicine, National and Kapodistrian University of Athens, Medical School, Laiko General Hospital, Athens, Greece

1.1 Definition

Diabetic foot is defined as the presence of infection, ulceration and/or destruction of deep tissues associated with neurologic abnormalities and various degrees of peripheral arterial disease () in the lower limb in patients with diabetes.

1.2 Epidemiology

The prevalence of foot ulceration in the general diabetic population is 4-10%, being lower (1.5-3.5%) in young and higher (5-10%) in older patients. The annual incidence of foot ulceration ranges from less than 1 to 3.6% among people with type 1 or type 2 diabetes. It is estimated that about 5% of patients with diabetes have a history of foot ulceration, whereas the lifetime risk for this complication today is between 19 and 34%. A selection of epidemiologic data on diabetic foot problems from large studies are summarized in Table 1.1. In a community-based study in the northwestern United Kingdom, the prevalence of active foot ulcers identified at screening among persons with diabetes was 1.7%, and the annual incidence was 2.2%. Higher annual incidence rates have been reported in specific populations: 6.0% among Medicare beneficiaries with diabetes, 5.0% among U.S. veterans with diabetes, and 6.3% in the global population of persons with diabetes.

Table 1.1 Epidemiological data on the diabetic foot.

Reference Country Population- or clinic-based Prevalence (%) Incidence Foot ulcers Amputation Foot ulcers Amputation Borssen et al. (1990) Sweden Population 0.75 - - - McLeod et al. (1991) UK Clinic 2.6 2.1 - - Walters et al. 1992 UK Population 7.4 - - - Moss et al. (1992) USA Population - 3.6 10.1a 2.1a Bouter et al. (1993) The Netherlands Population - - 0.8b 0.4 Siitonen et al. (1993) Finland Population - 0.5 Pendsey et al. (1994) India Clinic 3.6 - - - Kumar et al. (1994) UK Population 1.4 - - - Humphrey et al. (1996) Nauru Population - - - 0.76 Abbott et al. (2002) UK Population 1.7 1.3 2.2 - Mueller et al. (2002) The Netherlands Population - - 2.1 0.6 Centers for Disease Control and Prevention (2003) USA Population 11.8 - - - Lavery et al. (2003) USA Population - - 6.8 0.6 Manes et al. (2002) Balkan region Clinic 7.6 - - -

a Incidence over four years. Data from the Balkan region include Albania, Bulgaria, Greece, Romania, Serbia and the Former Republic of Macedonia.

b Include annual incidence of foot ulcers in patients hospitalized for foot problems.

There are ethnic differences in the prevalence of foot problems. Foot ulcers are more common in Caucasians than in Asian patients of the Indian subcontinent. This difference may be related to physical factors (a lower prevalence of limited joint mobility and lower plantar pressures in Asians) and to better foot care in certain religious groups such as Muslims. The risk for foot ulcers is higher in black, Native American and Hispanic American individuals in comparison to white Americans.

It is thought that foot ulcers are more common on the plantar aspect of the feet. However, clinic-based data from 10 European countries participating in the European Study Group on Diabetes and the Lower Extremity () project showed that 48% of the ulcers affect the plantar aspect of the feet, while 58% are in non-plantar areas. Similar findings have been reported by other authors.

The majority (60-80%) of foot ulcers will heal, 10-15% will remain active, and 5-24% will end up in amputation within a period of 6-18?months after first evaluation. Based on outcome data in specialized tertiary centers, approximately 77% of diabetic foot ulcers heal within one year. Unfortunately, even after the resolution of a foot ulcer, recurrence is common. It was estimated that roughly 40% of patients have a recurrence within one year after ulcer healing, almost 60% within three years, and 65% within five years. Interestingly, 3.5-13% of patients die with active ulcers, probably because the prevalence of co-morbidities such as coronary artery disease and nephropathy is high in patients with foot ulcers especially among those with neuro-ischemic ulcers. The risk of death at 10?years for a patient with diabetes who has had a foot ulcer is twice as high as the risk for a patient who has not had a foot ulcer. Neuropathic wounds are more likely to heal over a period of 20?weeks if they are smaller, of small duration and superficial. Neuro-ischemic ulcers take longer to heal and are more likely to lead to amputation. The patient's vascular status is the strongest predictor of healing rate and outcome.

The major adverse outcome of foot ulceration is amputation. Despite efforts at national levels, the rates of non-traumatic lower extremity amputation in people with diabetes remain 10-20-fold higher than in those without diabetes. Approximately 40-70% of all non-traumatic amputations of the lower limbs are performed on patients with diabetes. Many studies have documented the fact that foot ulcers precede approximately 85% of all amputations performed in patients with diabetes.

In addition, amputations in patients with diabetes are performed at a younger age. The risk for ulceration and amputation increases with both age and the duration of diabetes. According to one report, the prevalence of amputation in diabetic patients was 1.6% for the age range 18-44?years, 3.4% for ages 45-64 and 3.6% in patients over 65?years. The age-adjusted amputation rate for persons with diabetes (5.5 per 1000 persons) was 28 times that of those without diabetes (0.2 per 1000 persons) in 1997, increasing by 26% from 1990.

Regardless of diabetes status, these rates were higher for men than women and higher for Native Americans and non-Hispanic black individuals than Hispanic or non-Hispanic white patients. Lower amputation rates have been reported for South Asians and for African-Caribbean men. The higher prevalence of amputation may be due to aging of the diabetic population, the increasing prevalence of diabetes and better reporting. As the size of the diabetic population increases, more disease-related complications, and consequently more amputations, are expected in the future unless effective interventions aimed at preventing amputations are undertaken.

The efforts of some countries to reduce amputation rates are encouraging. An examination of recent time-trend national data from The Netherlands and Finland showed reductions in amputation rate of 40% between 1995 and 2000 and of 41% between 1984 and 2000, respectively. Data from Leverkusen, Germany, also showed a reduction in both the major and minor amputation rate in patients with diabetes by 37% between the years 1990 and 2005.

There is evidence that the decline in amputation rates is due to a better quality of foot care, including the provision of podiatrists, multidisciplinary foot teams and surgical interventions for lower extremity arterial disease. Clinic- and community-based studies have demonstrated that strategies aiming at patient education, identification of the foot at risk, implementation of preventive measures (proper footwear, podiatrist services) and multidisciplinary management can reduce the rate of amputation in patients with diabetes by almost 50%.

The most common cause of amputation in diabetes is ischemia and infection; critical limb ischemia or non-healing foot ulcer is the cause of amputation in 50-70% and infection in 30-50% of patients with...