Treating the diabetic foot

Rory Hafford looks at the links between diabetes and foot problems, and indentifies ways to prevent such complications and manage them if they arise

People with diabetes succumb to foot ulcers due to certain main factors, i.e. neuropathy, ischaemia or both. The problem can start as a result of mechanical injury or trauma. A vascular surgeon should be consulted as soon as possible, as infection can be both limb- and life-threatening.
According to Cavanagh et al (2007), infection is defined clinically, but wound cultures reveal the causative pathogens. Surgery to heal ulcers and prevent recurrence can include tenotomy, tendon lengthening, or reconstruction or total removal of body prominences. Ulcer recurrence rates are high in people with diabetes, but appropriate education for patients, the correct footwear and regular foot-care can reduce rates of re-ulceration.
Diabetic foot infections require attention to local and systemic issues and co-ordinated management, preferably by a multidisciplinary foot-care team. According to Lipskey et al (2004), aerobic gram-positive cocci (especially Staphylococcus aureus) are the predominant pathogens in diabetic foot infections.
Patients with diabetes who have chronic wounds, or who have recently received antibiotic therapy, may also be infected with gram-negative rods and those patients with foot ischaemia or gangrene may have obligate anaerobic pathogens.
Imaging studies may help diagnose or better define deep, soft-tissue purulent collections and are usually needed to detect pathological findings in bone. Plain radiography may be adequate in many cases, but magnetic resonance imaging (MRI) is more sensitive and specific, especially for detection of soft-tissue lesions.
When damage to the nervous system occurs, people with diabetes may not be able to feel their feet properly. Normal sweat secretion and oil production is impaired. These factors can lead to abnormal pressure on the skin, bones and joints of the foot, which can be exacerbated by walking and can, ultimately, lead to a breakdown of the skin of the foot.
Sores/ulcers can then develop. Damage to blood vessels and a compromised immune system makes it difficult to heal the foot wounds. Because of the poor blood-flow, antibiotics cannot get to the site of the infection easily and, if not managed quickly and properly, amputation looms.
Risk factors
l Poorly fitting shoes are a major problem. This can lead to sore spots, blisters, corns and calluses which can, in turn, develop into something more sinister.
If there is an underlying abnormality in the shape of the foot, i.e. hammer toes, or flat feet, prescription shoes could be considered;
l Peripheral neuropathy can mask signs and sores to which the person with diabetes would normally be alert. Consequently, a blister or a sore may go unnoticed for longer than it should, because the warning signs are not registering;
l Atherosclerosis can hamper proper blood flow to the site of damage;
l Common infections like athlete’s foot and toenail fungus should be treated as soon as possible;
l Smoking damage to the small blood vessels is a major problem and patients should be encouraged to quit as a matter of course. (See below for a more in-depth analysis of risk status.)
Treatments
The role of nitric oxide in diabetic wound healing is now under investigation by specialists. The vasodilator qualities of nitric oxide help bring nutrients to the oxygen-deficient wound beds. Light therapy such as low level laser therapy (LLLT) is now being used at centres around the world to treat diabetic ulcers.
In 2004, the Cochrane Review Panel concluded that for people with diabetic foot ulcers, hyperbaric oxygen therapy was indicated as it was found to reduce the risk of amputation and improved healing at year one.
Negative-pressure wound therapy is a vacuum used to remove excess fluid and cellular waste which, if left hanging around, can prolong the inflammatory phase of wound healing.
The results with this method have, up to now, been inconsistent – and a number of other factors need to be in play to ensure maximum outlook for the patient with diabetes: optimise the parameters of pressure intensity, timing and treatment intervals.
Growth factor is another treatment approach that is being used via matrix therapy or topical application, which regulate gene expression and, ultimately, the regeneration process.
Framework document
In 2006 a framework document was prepared in the UK for the provision of foot-care services for people with diabetes. It outlined a best-practice approach, considering the management of the diabetic foot under four headings:
l Routine basic assessment and care of the foot without any ulcer/lesion;
l Expert assessment and care of the foot that is at an increased risk, but that is currently not affected by an ulcer/lesion;
l Expert assessment and management of foot ulceration or lesion;
l Management of the person whose foot ulcer/lesion has resolved.
Risk status was also broken down under four headings:
l Identify the presence of sensory neuropathy (loss of ability to feel monofilament, vibration or sharp touch) and/or the abnormal build-up of callus;
l Identify when the arterial supply to the foot is reduced (absent foot pulses, signs of tissue ischaemia, symptoms of intermittent claudication);
l Identify deformities or problems of the foot (including bony deformities, dry skin, fungal infection) which may put it as risk;
l Identify other factors which may put the foot at risk (which may include reduced capacity for self care, impaired renal function, poor glycaemic control, cardiovascular and cerebrovascular disease).
The framework document suggested that the healthcare professional should also have the skills and knowledge necessary to:
l Discuss with the patient their individual level of risk and agree plans for future surveillance;
l Initiate appropriate referrals for expert review of those with increased risk;
l Advise on action to be taken in the event of a new ulcer/lesion arising;
l Advise on the use of footwear, which will reduce the risk of a new ulcer/lesion;
l Advise on other aspects of footcare in relation to diabetes, which will reduce the risk of a new ulcer/lesion.
In the foot presenting with ulcers/lesions, there is a recommended protocol in place that includes:
l Accurate assessment of the factors contributing to the presentation of the ulcer/lesion, including peripheral arterial disease, neuropathy, infection and relevant medical, personal and social factors;
l Appropriate management of any infection present;
l Appropriate further investigation of the patient (such as x-ray, magnetic resonance imaging and arterial imaging) and intervention (including surgical debridement) when indicated;
l Management of the patient’s wound bed in order to optimise the process of healing, including appropriate debridement and also the use of surface applications and dressings;
l Protection of the patient’s foot or lesion from trauma when indicated (including formal off-loading with total contact casts, commercial cast walkers or similar appliances);
l Appropriate management of the acute Charcot foot;
l That the management of other diseases, complications of diabetes and social and personal factors are considered;
l That the patient — and also their family and carers — are all made aware of the nature and implications of the condition and the principles of management;
l Continuing management and review by both specialist and non-specialist healthcare professionals, together with the patient and their carers, as appropriate.
Management of the person whose foot ulcer/lesion has resolved is a potentially tricky business because these people are at increased risk of developing another one.
Moreover, the average life expectancy is reduced in those diabetic patients who have already had a foot ulcer. This is primarily because of the risks posed by associated vascular disease and also other complications of diabetes. Consequently, the management of this stage of the condition is one of planned follow-up:
l Provision of specialist education for the patient and their carers;
l Advice on footwear (including the provision of orthoses);
l Minimising the impact of peripheral arterial disease;
l Minimising the risk imposed by peripheral neuropathy by debridement of callus and/or the provision of appropriate orthoses;
l Minimising the risk imposed by deformity or other problems of the foot, by initiating referrals to other specialists, if necessary;
l Arranging for continued surveillance and treatment as determined by the needs of the individual. This may best be achieved in a specialist clinic for those who have had previous ulcers/lesions;
l Also, the need for continued protection of the foot should be recognised by those healthcare professionals managing other aspects of the patient’s condition – and be integrated into their overall management plan.
Activity dosing
According to Dr David Armstrong (Professor of Surgery at the University of Arizona and Director of its Southern Arizona Limb Salvage Alliance), who spoke recently in the Royal College of Physicians in Dublin, the problem of the diabetic foot is such a preventable one.
Dr Armstrong believes that doctors need to work hard to push the spectrum of the diabetic foot problem more towards prevention rather than amputation. “If we can start dosing activity (physical activity) as well as we dose drugs, then I think we can make a difference. And I think this is starting to happen,” said the specialist physician.
“If you are pre-diabetic and you engage in moderate exercise – just walking up and down your street on a daily basis – you can cut the risk of developing this problem by as much as 50 per cent to 60 per cent,” he added.
Dr Armstrong also said that when someone needs to have a limb amputated, it is thought to be about as much of a blow to them as a diagnosis of cancer would be. However, he continued, we would not dream of withholding medication from people with lung cancer, breast cancer or any other form of the disease. And yet, when it comes to patients with diabetes and the potential loss of a limb, there is a pessimism that suggests that the loss of one limb will inevitably lead to the loss of another … and that is just the way it is.
But, said Dr Armstrong, it should not be this way and the medical profession needs to work to counter this pessimism.
Maggots
No feature on treating and managing the diabetic patient wit foot problems would be complete without a word on maggot therapy. One of the latest studies on this controversial issue (Sherman, 2002. Diabetic Care journal) found that the enthusiasm for maggot debridement has been fuelled more by anecdotal reports and personal experience than by scientific studies.
However, this study also demonstrated that maggot therapy is more effective and efficient in debriding non-healing foot and leg ulcers in males with diabetes than does the typical conventional treatment.
Maggot therapy was also associated with a more rapid decrease in wound size and an increase in granulation tissue, making the wounds ready for surgical closure. The findings of the study support the benefits of maggot therapy.