The Diabetic Foot


English: The foot of a person with Charcot-Mar...

The foot of a person with Charcot with lack of muscle, high arch, and hammer toes.

 Every 30 seconds a lower limb is lost somewhere in the world because of complications related to diabetes. Amputation is the last resort management of diabetic ulceration of a limb that has gone horribly wrong because of uncontrolled infection or ischaemia leading to gangrene.

Foot ulcers can occur in nearly one fifth of diabetics. Ulceration is completely preventable and treatable and should never progress to this level of morbidity. But it does progress on occasion, and if not detected early, then it may progress to considerable permanent morbidity.

The risk factors for diabetic foot ulceration include the presence of other diabetic complications, such as diabetic retinopathy or eye damage, being elderly, having a history of foot ulcers or amputation, being on dialysis, and having poor glycaemic control.

Incidence of Foot Complications

Diabetes related foot complications are on the increase and are common. Fortunately, not many diabetic patients require limb amputation, but good management is required and the lower limbs should not be neglected. Regular monitoring and good foot care are an essential and good preventative strategy.

Foot problems are a common cause of prolonged hospitalization for diabetics. In the UK

Ulcus bei Diabetes über dem Hallux

Foot ulcer in a diabetic. (Photo credit: rosmary)

they are responsible for one fifth of diabetes related hospitalizations. If not treated properly, the ulcerated foot can progress to a condition of chronic debilitation with a very poor prognosis for the patient.

Prevention of Diabetic Foot Ulcers

Diabetic foot ulcers are entirely preventable. Primary prevention of this diabetic complication is very achievable, but secondary prevention is also an important aspect of good foot care. Having a previous ulcer is strongly predictive of getting another.

Causes of Foot Problems

Diabetics are at increased risk of foot problems for a number of reasons, and there is a range of risk factors for diabetes related ulceration of the extremities.

The most common cause of foot ulceration is loss of foot sensation or neuropathy. Diabetic neuropathy is caused by nerve damage, which is related to a prolonged period of uncontrolled hyperglycaemia.

In those with lower extremity nerve damage or neuropathy, there is loss of feeling in the limb. This can lead to abnormal weight been put on the foot due to the lack of sensitivity, and thus an increased risk of damage.

The foot with nerve damage can feel warm and it does not always hurt, so the patient is reassured. Furthermore, perhaps they don’t recognize the damage that is being done with repeated trauma, even if it is not significant or only minor injury. Some patients may have a warm foot, so they think there is not anything seriously wrong with them.

Wearing inappropriate footwear is also a risk factor for ulceration. This causes trauma and can trigger subsequent deformity, such as clawing of the toes or plantar prominence of the metatarsal head. Deformity of the foot leads to an increased risk of damage, especially if the patient does not wear protective footwear.

Charcot foot is a condition caused by diabetic neuropathy. It involves progressive degeneration of a weight bearing joint with bone loss or destruction. As there is associated decreased peripheral sensation, the Charcot foot can go unchecked and unmanaged. This can lead to subsequent structural damage, ulceration, infection and eventual amputation. The precipitation of the Charcot foot can be in some cases only a minor trauma, and may not even be remembered by some patients.

Other contributory factors that predispose to foot trauma or damage, particularly in the elderly, include poor vision, poor mobility, and the presence of cardiovascular disease or cerebrovascular disease.

In the diabetic who is obese and lives a very sedentary existence, and does very little or no exercise, excessive trauma force on a vulnerable foot or lower limb is more likely to trigger or exacerbate an existing diabetic foot problem.

In some developing countries, where diabetic foot often co-exists with leprosy, walking barefoot may be a factor in causing foot problems.

Prevention of Diabetic Foot Ulcers

The most important prevention strategy is to educate the patient to adopt healthy foot-care practices and to use appropriate footwear. Regular foot checks of the diabetic patient are recommended to prevent the onset of ulceration. Special footwear and regular treatment of calluses will help prevent ulcer development.

Having adequate podiatry services is a must. In Sweden, a 78% decrease, and the Netherlands, a 37% decrease, there have been significant reductions in foot amputations in diabetics recorded with the introduction of improved podiatry services. Education is also important, but not in isolation, as it has been shown to have limited benefit without backup podiatry.

Identifying Patients at Risk

Simple tools and a clinical examination of the foot can be used to identify the diabetic patient who has a foot that is at high risk of ulceration. These include the monofilament test, sensory testing scores and reflexes.

Electrophysiology is not needed to identify the high risk patient. The most important thing to do is to take off the shoes and socks and examine the feet.

Some of the characteristics of a foot that is at increased risk of developing ulceration include:

  • Loss of proprioception, instability and gait abnormalities.
  • Charcot foot.
  • Callus due to autonomic dysfunction
  • Decreased blood flow.
  • Loss of sensation.
  • Increased callus ratio in weight bearing areas.
  • Muscle wasting and dystrophic nails
  • High arch foot.
  • Clawing of the toes.

Examination of the Diabetic Foot

High foot pressures are associated with first and recurrent plantar neuropathic ulcers. Foot pressure abnormalities occur early. High foot pressures predict the development of ulceration in the high risk neuropathic foot.

Simple observation of callus tissue under a high pressure area in the neuropathic foot is associated with a 70-fold increased risk of developing a foot ulcer at that particular site. Plantar callus, skin thickening at the heel bone connection with the toes, is associated with high foot pressure and is a strong predictor of ulceration.

A footprint mat (PressureStat) is a simple way to identify plantar abnormalities associated with diabetes. It creates an exact replica in shadow form of the high pressure areas of the diabetic patient’s foot, so it is easy to see what areas of their foot need to be checked and monitored for signs of ulceration. Patients can even take it home and refer to it.

Treatment of the Ulcer

The diabetic foot ulcer should heal if there is adequate arterial blood flow, infection is adequately managed, and pressure is removed from the wound and its margins.

The aims are to try and correct the underlying condition and facilitate any ulcer or wound healing:

  • Controlling infection.
  • Debridement and good wound dressing practice.
  • Negative pressure and hyperbaric oxygen.
  • Offloading the limb.
  • Vascular reconstruction.

Managing Foot Infections

Diabetics are more prone to infections because of foot damage and often compromised blood supply to the lower extremities. Infections range from simple superficial skin infections or cellulitis to severe osteomyelitis with infection in the soft tissues and bone.

Managing infection is an important aspect of foot ulcer care and it is important to do cultures for accurate diagnosis. Inappropriate use of broad-spectrum antibiotics is not recommended. Targeted and infection appropriate antibiotic treatment is vital to the success of treatment.

Foot infections in diabetics can also be difficult to treat because of the poor blood supply and damage to the structure of the foot. This results in poor and often ineffective antibiotic concentration at the infection site. Similarly, the body’s own healing processes are often impaired. As well as this, there is the complication of the risks of further incidental trauma to the infection site because of loss of feeling in the area, so patient education about this risk will improve the chances of healing. They can take care to avoid any activities that might lead to trauma.

Superficial infections respond best to antibiotic treatment, but more serious infection of the underlying tissues or bone will require thorough debridement for antibiotic treatment to be successful.

Debridement of Lesions

Wound bed preparation involves providing thorough debridement of the ulcerous area as this speeds healing. Debridement removes infected and nonviable tissue, and may stimulate the release of endogenous growth factors. Debridement should be down to normal and healthy tissue. Aggressive debridement removes all the callous tissue and any bony fragments that may impede antibiotic penetration to the infection site. Debridement might also be a part of follow-up care. Larval therapy using maggots is a possible future wound cleaning approach.

Use of Negative Pressure Therapy and Hyperbaric Oxygen

Negative pressure is a noninvasive therapy that has been used to assist wound closure, and it involves using a vacuum to remove fluid and debris from the wound site. This reduces inflammation and results in more rapid formation of granulation tissue. There is some evidence that hyperbaric oxygen therapy reduces the risk of amputation and it may improve wound healing.

Offloading the Limb

Total immobilisation of the diabetic patient while the foot ulcer takes the time to heal is completely impractical. Offloading is a major problem and patients frequently neglect to do it. The reason they got a foot ulcer is that cant feel it and they walk on it. The foot never hurts so they don’t realize that there are good reasons why should they offload it.

Research has shown that patients with total contact casts do better than those with removable casts. The total contact cast has advantages because it forces adherence to offloading and reduces activity. It does not reduce pressure but redistributes it and reduces it over the ulcer area. Removable casts have the disadvantage that they can be removed and they are thus not worn all of the time leading to problems with adherence

Managing the Ischaemic Foot

In those patients with foot ulcers caused by impeded blood supply to the foot who also have foot numbness, a vascular intervention approach may be considered to prevent further foot damage. The most commonly used interventions are surgical arterial bypass and increasingly balloon angioplasty and stents.

Vascular reconstruction can also be required to manage the acutely infected ischaemic foot, particularly in the case of the severe neuroischaemic infection called wet necrosis.

Future Treatments of diabetic foot ulcers

The key to the development of new treatments is a better understanding of the wound healing process.

In the future, stem cell therapies may be used in the diabetic foot or perhaps growth factors will be given together with tissue inhibitors or matrix metalloproteinases.

Gene expression and gene therapy is a very exciting area with many potential applications in the field such as the use perhaps in a simple test for infection.

Use of maggot larval cultures against antibiotic resistant infections, such as MRSA, needs to be considered, as they are very good at cleaning out wounds and have bacteriostatic secretions and clear MRSA.

Conor Caffrey is a writer on health, science and medicine

Other articles by Conor Caffrey about diabetes

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