The Foot in Diabetes

Andrew J. M. Boulton, Gerry Rayman, Dane K. Wukich, Andrew J. M. Boulton, Gerry Rayman, Dane K. Wukich

• Publisher: Wiley-Blackwell
• Year: 2020
• ISBN:
  9781119445838
• Edition: 5
• Topic: Medicina
• Subtopic: Endocrinología y metabolismo

Fully revised and updated edition of this popular book, addressing all issues concerning the diabetic foot, one of the most prevalent problems in diabetes, with a strong emphasis on practical aspects of delivering care.

1
Epidemiology and Economic Impact of Foot Ulcers

Edward J. Boyko¹ and Matilde Monteiro‐Soares²

¹ VA Puget Sound Healthcare System and the University of Washington, Seattle, WA, USA

² MEDCIDS and CINTESIS, Faculty of Medicine, University of Porto, Porto, Portugal

1.1 Introduction

Diabetes mellitus accounts for the majority of nontraumatic lower limb amputations [1], despite affecting a minority (9.4%) of the U.S. population [2]. A systematic review of risk of lower limb amputation in persons with and without diabetes in a defined population yielded 19 publications reporting results from Europe, UK and the US with relative risk of amputation in diabetes ranging from 7.4 to 41.3 [3]. Notably this range of relative risks for amputation exceeds that for diabetes and fatal coronary heart disease of 3.5 (women) and 2.1 (men) from a meta‐analysis of 37 prospective studies [4], and is of similar magnitude to that seen for the association between ever smoking and lung cancer [5]. The chief antecedent to diabetic lower limb amputation is the nonhealing foot ulcer [6], which precedes approximately 80% of diabetic amputations, and which has been reported to lead to amputation in 15% of cases [7–9]. The problem of higher amputation risk in diabetes can be traced backwards in the causal chain of events to the development of a diabetic foot ulcer (DFU) [6].

1.2 Diabetic Foot Ulcer (DFU) Definition

Diabetic Foot Ulcer (DFU) is defined as a full thickness skin defect below the ankle that is slow to heal or non‐healing. Amongst 1000 patients with DFU enrolled in the Eurodiale Study and followed for up to one year, median time to healing was 147 days for toe (95% CI 135–159 days), 188 days for midfoot (95% CI 158–218 days) and 237 days for heel ulcers (95% CI 205–269 days) [10], with healing success at one year of 79% for plantar and 73% for non‐plantar ulcers. The available data demonstrate prolonged healing times for DFU and the frequent occurrence of healing failure.

The study of the epidemiology of DFU or any health condition requires a case definition to identify afflicted persons. There is no established case definition for DFU in general use. Definitions of DFU in the published literature may include features such as full thickness skin defect distal to the malleoli, but in some reports no case definition is provided with the identification of DFUs left to the judgement of foot care providers; or through review of podiatry records or electronic medical record data. Although delayed healing is a recognized feature of DFU, there is no established criterion for ‘slow to heal’ and rarely is a duration criterion included in the ulcer definition. The Seattle Diabetic Foot Study required a healing time greater than 14 days to meet the criteria for a DFU [11], whilst a clinical trial of custom footwear specifically mentioned that duration of ulceration was not be taken into consideration [12]. Consensus on a DFU definition would enable comparisons of the frequency of this complication across populations, regions, and over time.

1.3 DFU Classification

DFU classification systems function as a guide to the best treatment and as a predictor of the probability of wound healing and the need for amputation. The typical components of a wound classification system include wound depth, presence and severity of infection, gangrene, and ischemia. A systematic review of DFU classification systems identified 15 such systems reported in 25 articles [13]. Examples of the systems for which the greatest number of validation studies have been performed are the Meggitt‐Wagner (9 validations), and the University of Texas and S(AD)SAD systems (5 validations each). Features of these three systems are seen in Table 1.1.

Comparisons of the ability of different classification systems have generally found them to be predictive of healing and amputation [14, 15].

Little research has been conducted comparing these classification systems using methods commonly employed for other diagnostic modalities such as comparison of area under receiver operating characteristic curves (AUROC), or by comparing test characteristics that alter pre‐test probability, such as likelihood ratios [16, 17]. Jeon et al. compared five different DFU classification systems on the ability to predict amputation [18] that included the systems shown in Table 1.1, except that a simplified version of the S(AD)SAD system was used (SINBAD). All systems showed excellent ability to predict amputation with AUROC ranging from 0.85 to 0.89, and positive and negative likelihood ratios ranging from 4 to 18 and 0.21 to 0.41, respectively. Monteiro‐Soares et al. compared 11 different prediction models for lower limb amputation in a prospective study of 293 patients with DFU and found positive and negative likelihood ratios ranging from 1.0 to 5.9, and 0.1 to 0.9, respectively, and AUROC curves ranging from 0.53 to 0.83, indicating that considerable diversity exists with some models showing significantly poorer prediction performance [19]. Further research is needed comparing existing classification systems to predict healing and amputation in patients with DFU.

DFUs are often described without using a classification system, but in reference to likely ulcer aetiology (neuropathic versus ischemic versus both) or foot location [20]. Ulcers usually develop over bony prominences that can be found on the plantar and dorsal foot surfaces especially if a structural deformit...