Chapter 32: Foot Care
Canadian Diabetes Association 2013 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada
- Foot complications are a major cause of morbidity and mortality in persons with diabetes and contribute to increased healthcare utilization and costs.
- In populations with diabetes, individuals with peripheral neuropathy and peripheral arterial disease (PAD) are predisposed to foot ulceration and infection, which ultimately may lead to lower-extremity amputation.
- Characteristics that have been shown to confer a risk of foot ulceration in persons with diabetes include peripheral neuropathy, previous ulceration or amputation, structural deformity, limited joint mobility, PAD, microvascular complications, high glycated hemoglobin (A1C) levels and onychomycosis.
- Loss of sensation over the distal plantar surface to the 10-g Semmes Weinstein monofilament is a significant and independent predictor of future foot ulceration and the possibility of lower-extremity amputation.
- The University of Texas Diabetic Wound Classification System has been validated as a predictor of serious outcomes in patients with diabetes with foot ulcers
- In persons with diabetes with underlying ischemia, the distribution of PAD is greater in the arterial tree below the knee than is seen in those without diabetes.
- Noninvasive assessments for PAD in diabetes include:
- Ankle-brachial blood pressure index (ABI), but should be avoided in those with medial arterial wall calcification in lower extremities due to potential underestimation of peripheral arterial obstruction;
- Photoplethysmography (PPG), which measures systolic toe pressure based on the intensity of light reflected from the skin surface and the red cells below and is recommended for those with medial arterial wall calcification in lower extremities;
- Transcutaneous oximetry (tcPO2);
- Doppler arterial flow studies.
- For patients with suspected lower-limb ischemia:
- Intra-arterial digital subtraction contrast arteriography has provided the most definitive assessment of PAD but may precipitate renal failure in individuals with higher degrees of renal insufficiency.
- Advanced magnetic resonance angiography (MRA) and computed tomographic angiography (CTA) do not require arterial access. However, caution should be exercised when injecting intravenous radiocontrast dye or gadolinium-based contrast agents in persons with renal insufficiency so as to avoid precipitating acute renal failure.
- In people with diabetes, foot examinations by healthcare providers should be an integral component of diabetes management to identify persons at risk for ulceration and lower-extremity amputation [Grade C, Level 3] and should be performed at least annually and at more frequent intervals in those at high risk [Grade D, Level 4]. Assessment by healthcare providers should include the assessment of skin changes, structural abnormalities (e.g. range of motion of ankles and toe joints, callus pattern, bony deformities), skin temperature, evaluation for neuropathy and PAD, ulcerations and evidence of infection [Grade D, Level 4].
- The foot examination should include the assessment of skin temperature since increased warmth is the first indicator of inflammation in an insensate foot and also may be the first sign of acute Charcot neuroarthropathy resulting from the loss of protective sensation in the foot.
- In addition, an acute Charcot foot may be associated with erythema and swelling.
Management and Preventative Care
- People at high risk of foot ulceration and amputation should receive foot care education (including counselling to avoid foot trauma), professionally fitted footwear and early referrals to a healthcare professional trained in foot care management if foot complications occur [Grade C, Level 3].
- The prevention of amputations involves regular foot examination and evaluation of amputation risk, regular callus debridement, and early detection and treatment of diabetic foot ulcers.
- Individuals who develop a foot ulcer should be managed by a multidisciplinary healthcare team with expertise in the management of foot ulcers to prevent recurrent foot ulcers and amputation [Grade C, Level 3].
- Generally, the management of foot ulceration should address glycemic control, pressure relief/offloading, infection, lower-extremity vascular status and local wound care.
- There is currently insufficient evidence to recommend any specific dressing type for diabetic foot ulcers [Grade C, Level 3]. General principles of wound management involve the provision of a moist wound environment, debridement of nonviable tissue (nonischemic wounds) and offloading of pressure areas [Grade B, Level 3].
- In general, wound dressings that maintain a moist wound environment should be selected.
- There is, however, some evidence to support negative pressure wound therapy (NPWT) as a postoperative intervention after extensive debridement.
- Evidence is currently lacking to support the routine use of adjunctive wound-healing therapies, such as topical growth factors, granulocyte colony-stimulating factors, dermal substitutes or HBOT in diabetic foot ulcers, but they may be considered in nonhealing, nonischemic wounds when all other options have been exhausted [Grade D, Level 4].
- Pressure offloading may be achieved with temporary footwear until the ulcer heals and the foot stabilizes.
- Removable and irremovable cast walkers and total contact casting are effective as pressure-reducing devices in plantar surface ulcers, though total contact casting requires careful individual selection and personnel training due to its potential for complications.
- Where bony foot deformities prevent the fitting of appropriate footwear and/or offloading of pressure-related ulcers, consultation with a surgeon skilled in foot surgery may be considered to address the deformity.
- Treatment of the acute Charcot foot requires immobilization of the foot for several months, in a total contact cast or removable walker device until foot temperatures normalize. Further studies are necessary to evaluate the use of bisphosphonates in the routine treatment of Charcot arthropathy.
- Infection may complicate foot ulcers and may progress rapidly to become limb and/or life threatening.
- When infections first begin, the most frequently encountered pathogens include Staphylococcus aureus, Streptococcus pyogenes (group A streptococcus) and Streptococcus agalactiae (group B streptococcus).
- With time and the presence of devitalized tissue, gram-negative and anaerobic pathogens also can play a role in the process, leading to polymicrobial infections.
- Specimens for culture from the surface of wounds, as opposed to deeper tissues obtained by debridement, are unreliable in determining the bacterial pathogens involved.
- Empiric treatment may include broad spectrum antibiotics, with subsequent antibiotic selection tailored to the sensitivity results of cultured specimens.
- Uncontrolled diabetes can result in immunopathy with a blunted cellular response to infection. Up to 50% of patients with diabetes who have a significant limb infection may not have systemic signs of fever or leukocytosis at presentation.
- Deep infections require prompt surgical debridement in addition to appropriate antibiotic therapy.
- Distal limb revascularization and endovascular techniques with angioplasty and stenting in infrainguinal arteries have potential benefit in long-term limb salvage.
- Certain subpopulations with diabetes on insulin therapy have poorer outcomes after revascularization than those on oral anithyperglycemic therapy, perhaps reflecting a greater association of comorbidities.
For definitions of the levels of evidence cited in this chapter, please refer to the Guideline Recommendations: Levels of Evidence.
If you would like more details on this topic, please visit the Canadian Diabetes Association Clinical Practice Guidelines: Chapter 32. For a diabetes and foot care patient checklist, see Appendix 9. For more information on the management of foot ulcers, see Appendix 10.