1 Epidemiology and Economic Impact of Foot Ulcers

In the year 2005, most of the estimated 150 million people worldwide afflicted by diabetes mellitus lived in developing countries.1 Diabetic foot ulcers will complicate the disease in more than 15 % of these people during their lifetimes.2,3 In prospective cohort studies conducted among those with diabetes, history of a foot ulcer increased the risk of subsequent amputation by two- to over three-fold.4,5 Foot ulcers precede more than 80 % of non-traumatic lower limb amputations.6 In this chapter, we will review the definition of a ‘foot ulcer ’ and the studies that estimate the incidence and prevalence of foot ulcers, making note of issues that need to be considered in their computation. We will also review risk factors for foot ulcers from well-conducted epidemiological studies, foot ulcer outcomes and the economic impact of foot ulcers. FOOT ULCER DEFINITION AND CLASSIFICATION In order to estimate accurately the occurrence of diabetic foot ulcers and risk factors associated with this diabetic complication, a common definition is needed. The International Consensus on the Diabetic Foot currently defines a diabetic foot ulcer as a full-thickness wound below the ankle in a patient with diabetes, irrespective of duration.7 The International Working Group on the Diabetic Foot (IWGDF) also recommends that studies describing the occurrence of diabetic foot ulcers use a standard classification system to facilitate communication between health care providers, provide information about the healing potential of an ulcer and help guide management decisions. Use of such a system allows a patient to be followed up over time, allowing repeated classification of the foot ulcer. Classification systems should be sufficiently robust that intra- and inter-observer variability is low (i.e. the classification is reproducible) and should be applicable worldwide. This allows research results from one study to be compared to those of others, which is important in interpretability of results.8 For foot ulcers, one challenge in this regard has been the numerous classification systems in existence. The most commonly used system internationally is Wagner’s.9 This system specifies ulcer depth and the presence of osteomyelitis or gangrene as a five-grade continuum