Diabetic foot

What is diabetic foot?¹

People with diabetes are at increased risk of peripheral arterial disease and diabetic neuropathy, as well as having a higher risk of developing infections and decreased ability to clear infections. Therefore, people with diabetes are prone to frequent and often severe foot problems and a relatively high risk of infection, gangrene and amputation.

Motor, sensory and autonomic fibres may all be affected in people with diabetes mellitus.

• Because of sensory deficits, there are no protective symptoms guarding against pressure and heat and so trauma can initiate the development of a leg ulcer.

• Absence of pain contributes to the development of Charcot foot (see below), which further impairs the ability to sustain pressure.

• Motor fibre abnormalities lead to undue physical stress and to the development of further anatomical deformities (arched foot, clawing of toes), and contribute to the development of infection.

• When infection complicates a foot ulcer, the combination can be limb-threatening or life-threatening.

• Detection and surveillance of diabetic neuropathy are an essential routine part of a diabetic annual review.

How common are diabetic foot problems? (Epidemiology)²

• Foot complications are common in people with diabetes. It is estimated that 10% of people with diabetes will have a diabetic foot ulcer at some point in their lives.

• An annual incidence of 2.2% was found in a large community survey in the UK and in up to 7.2% in patients with neuropathy.

• Painful diabetic neuropathy is estimated to affect between 16% and 26% of people with diabetes.³

• Diabetes is the most common cause of non-traumatic limb amputation, with diabetic foot ulcers preceding more than 80% of amputations in people with diabetes.

• The incidence of major amputation is between 0.5 and 5.0 per 1,000 people with diabetes.

• After a first amputation, people with diabetes are twice as likely to have a subsequent amputation as people without diabetes.

Risk factors⁴

• Risk factors for foot ulceration include peripheral arterial disease, peripheral neuropathy, previous amputation, previous ulceration, presence of callus, joint deformity, problems with vision and/or mobility, and male sex.

• Risk factors for peripheral arterial disease include smoking, hypertension and hypercholesterolaemia.

Aetiology⁵

• People with diabetes develop foot ulcers because of neuropathy, ischaemia or both.

• The initiating injury may be from acute mechanical or thermal trauma or from repetitively or continuously applied mechanical stress:
  

  • Peripheral neuropathy in people with diabetes results in abnormal forces being applied to the foot, which diabetic ischaemia renders the skin less able to withstand.

  • Other complications contributing to the onset of ulceration include poor vision, limited joint mobility, and the consequences of cardiovascular and cerebrovascular disease.

  • However, the most common precipitant is accidental trauma, especially from ill-fitting footwear.

• Once the skin is broken, many processes contribute to defective healing, including bacterial infection, tissue ischaemia, continuing trauma, and poor management.

• Infection can be divided into:

  • Superficial and local.

  • Soft tissue and spreading (cellulitis).

  • Osteomyelitis.

• Typically, more than one organism is involved, including Gram-positive, Gram-negative, aerobic and anaerobic species. Staphylococcus aureus is the most common pathogen in osteomyelitis.

Symptoms of diabetic foot ulcers

• Diabetic foot ulcers are usually painless, punched-out ulcers in areas of thick callus ± superadded infection, pus, oedema, erythema, crepitus, malodour.

• Neuro-ischaemic ulcers tend to occur on the margins of the foot; neuropathic ulcers tend to occur on the plantar surface of the foot.

• Neuropathic foot tends to be warm with dry skin, bounding pulses, distended veins, reduced sensation and callus around the ulcer.

• Neuro-ischaemic foot tends to be cool and pink with atrophic skin and absent pulses; the foot may be painful and there is little callus.

Charcot foot

See also the separate Neuropathic Joints (Charcot Joints) article.

A Charcot foot is a neuro-arthropathic process with osteoporosis, fracture, acute inflammation and disorganisation of foot architecture. Suspected Charcot neuro-arthropathy of the foot is an emergency and should be referred immediately to a multidisciplinary foot team.⁴

• The Charcot foot is characterised by bone and joint degeneration which can lead to a devastating deformity. It usually presents as a hot swollen foot after minor trauma.

• Slight trauma triggers fracture of a weakened bone, which increases the load on adjacent bones, leading to gross destruction. The process is self-limiting but the persisting deformity greatly increases the risk of secondary ulceration.

• Plain X-ray may be normal but a bone scan may show a hot spot.

• Damage and developing deformity should be limited by immobilising the foot in a cast; realignment arthrodesis of the hind foot can sometimes prevent amputation.

Assessment²

For adults with diabetes, assess their risk of developing a diabetic foot problem at the following times:

• When diabetes is diagnosed and, thereafter, at least annually.

• If any foot problems arise.

• On any admission to hospital and, while in hospital, if there is any change in their status.

When examining the feet of a person with diabetes, remove their shoes, socks, bandages and dressings. Examine both feet for evidence of the following risk factors:

• Neuropathy (use a 10 g monofilament as part of a foot sensory examination).

• Limb ischaemia.

• Ulceration.

• Callus.

• Infection and/or inflammation.

• Deformity.

• Gangrene.

• Charcot arthropathy.

Assess the person's current risk of developing a diabetic foot problem or needing an amputation using the following risk stratification:

Low risk
No risk factors present except callus alone.

Moderate risk

• Deformity; or

• Neuropathy; or

• Non-critical limb ischaemia.

High risk

• Previous ulceration; or

• Previous amputation; or

• On renal replacement therapy; or

• Neuropathy and non-critical limb ischaemia together; or

• Neuropathy in combination with callus and/or deformity; or

• Non-critical limb ischaemia in combination with callus and/or deformity.

Active diabetic foot problem

• Ulceration; or

• Spreading infection; or

• Critical limb ischaemia; or

• Gangrene; or

• Suspicion of an acute Charcot arthropathy, or an unexplained hot, red, swollen foot with or without pain.

Children with diabetes who are aged under 12 years and their family members or carers should be provided with basic foot care advice. For young people with diabetes who are aged 12-17 years, the paediatric care team or the transitional care team should assess the young person's feet as part of their annual assessment and should provide information about foot care. If a diabetic foot problem is found or suspected, the paediatric care team or the transitional care team should refer the young person to an appropriate specialist.

Diabetic foot treatment²

For people who are at low risk of developing a diabetic foot problem, continue to carry out annual foot assessments, emphasise the importance of foot care and advise them that they could progress to moderate or high risk. Refer people who are at moderate or high risk of developing a diabetic foot problem to the foot protection service.

Management of the diabetic foot includes:

• Education, including the importance of routine preventative podiatry care and use of appropriate footwear. The person should check their feet every day and report any sores or cuts that do not heal, any puffiness or swelling and any skin that feels hot to the touch.

• Control of glucose, blood pressure and cholesterol; smoking cessation and weight control.

• Risk assessment.

• Mechanical foot interventions to prevent ulceration.

• Antibiotics to manage and prevent infection.

• Management of peripheral arterial disease, including bypass surgery.

• Wound management, including keeping the wound dry and debridement of dead tissue.

Patient education²

• Methods to help self-examination/monitoring; daily examination of feet for problems (colour change, swelling, breaks in the skin, pain or numbness).

• The importance of well-fitting and comfortable footwear; regular checking of footwear for areas that will cause friction or other problems; seeking help from a healthcare professional if footwear causes difficulties or problems; wearing specialist footwear if it has been prescribed/supplied.

• Hygiene (daily washing and careful drying); moisturising areas of dry skin.

• Nail care.

• Dangers associated with practices such as skin removal; dangers associated with over-the-counter preparations for foot problems.

• When to seek advice from a healthcare professional: if there are any colour changes, swelling, breaks in the skin, corns or calluses, pain or numbness, or if self-care and monitoring are not possible or difficult (eg, because of reduced mobility).

• Possible consequences of neglecting the feet: potential complications and the benefits of prevention and prompt detection and treatment.

• For people at increased, or high, risk of foot ulcers; in addition to the above:
  

  • If neuropathy is present, extra care and vigilance are needed, with additional precautions to keep the feet protected.

  • The patient should not walk barefoot.

  • Seeking help to deal with potential burning of numb feet: check bath temperatures; avoid hot water bottles, electric blankets, foot spas and sitting too close to fires.

  • Additional advice about foot care on holiday: not wearing new shoes; planning adequate rest periods to avoid additional stress on the feet; the importance of walking up and down aisles when travelling by air; use of sun block on the feet; having a first aid kit and covering any sore places with a sterile dressing; seeking help if problems develop.

• For people with foot ulcers:
  

  • The importance of early detection and prompt treatment.

  • Appropriate resting of the foot/leg.

  • Reporting any changes in the ulcer or surrounding skin, discharge, foot smells, swelling or generally feeling unwell and/or poor glucose control.

Foot assessment as part of routine diabetic care²

• Effective care involves a partnership between patients and professionals. All decision making should be shared.

• Organise a recall system. Arrange recall and annual review as part of ongoing care.

• As part of annual review, trained personnel should examine patients' feet to detect risk factors for ulceration. All people with diabetes should be regularly screened to assess their risk of developing a foot ulcer.⁴

• Examination of patients' feet should include:
  

  • Testing of foot sensation, using a 10 g monofilament or vibration.

  • Palpation of foot pulses.

  • Inspection of any foot deformity and footwear.

  • Classification of foot risk as (if the patient has had any previous foot ulcer or deformity or skin changes, manage as high-risk): low current risk, moderate-risk, high-risk and active diabetic foot problem.

• Risk stratification: the Scottish Intercollegiate Guidelines Network (SIGN) guideline classifies risk as:⁴
  

  • Low: no risk factors present - eg, no loss of sensation, no signs of peripheral arterial disease and no other risk factors.

  • Moderate: one risk factor present - eg, loss of sensation, or signs of peripheral arterial disease without callus or deformity.

  • High: previous ulceration or amputation or more than one risk factor present - eg, loss of sensation, or signs of peripheral arterial disease with callus or deformity.

  • Active: presence of active ulceration, spreading infection, critical ischaemia, gangrene or unexplained hot, red, swollen foot with or without the presence of pain.

• For people who are at low risk of developing a diabetic foot problem, continue to carry out annual foot assessments, emphasise the importance of foot care and advise them that they could progress to moderate risk or high risk.

• For people at moderate or high risk of developing a diabetic foot problem, the foot protection service should:

  • Assess the feet.

  • Give advice about - and provide - skin and nail care of the feet.

  • Assess the biomechanical status of the feet, including the need to provide specialist footwear and orthoses.

  • Assess the vascular status of the lower limbs.

  • Liaise with other healthcare professionals (for example, the person's GP) about the person's diabetes management and risk of cardiovascular disease.

• Depending on the person's risk of developing a diabetic foot problem, carry out reassessments at the following intervals:

  • Annually for people who are at low risk.

  • Frequently (for example, every 3-6 months) for people who are at moderate risk.

  • More frequently (for example, every 1-2 months) for people who are at high risk, if there is no immediate concern.

  • Very frequently (for example, every 1-2 weeks) for people who are at high risk, if there is immediate concern.

  • Consider more frequent reassessments for people who are at moderate or high risk and for people who are unable to check their own feet.

Each review should include inspection of the patient's feet, including skin and nail care, consideration of the need for vascular assessment, evaluation of the patient's footwear and taking the opportunity to enhance foot care education.

Referral²

If a person has a limb-threatening or life-threatening diabetic foot problem, refer them immediately to acute services and inform the multidisciplinary foot care service. Examples of limb-threatening and life-threatening diabetic foot problems include:

• Ulceration with fever or any signs of sepsis.

• Ulceration with limb ischaemia.

• Clinical concern that there is a deep-seated soft tissue or bone infection (with or without ulceration).

• Gangrene (with or without ulceration).

For all other active diabetic foot problems, refer the person within one working day to the multidisciplinary foot care service or foot protection service (according to local protocols and pathways) for triage within one further working day.

Suspect acute Charcot arthropathy if there is redness, warmth, swelling or deformity (in particular, when the skin is intact), especially in the presence of peripheral neuropathy or chronic kidney disease. Think about acute Charcot arthropathy even when deformity is not present or pain is not reported. To confirm the diagnosis of acute Charcot arthropathy, refer the person within one working day to the multidisciplinary foot care service for triage within one further working day. Offer non-weight-bearing treatment until definitive treatment can be started by the multidisciplinary foot care service.

Diabetic foot ulcer^{2 6}

Diabetic foot ulcers are associated with significant morbidity and mortality and can lead to hospitalisation and lower-limb amputation if not recognised and treated in a timely manner.

If a person has a diabetic foot ulcer, assess and document the size, depth and position of the ulcer. Use a standardised system to document the severity of the foot ulcer, such as the SINBAD (Site, Ischaemia, Neuropathy, Bacterial infection, Area and Depth) or the University of Texas classification system. Do not use the Wagner classification system to assess the severity of a diabetic foot ulcer.

Offer 1 or more of the following as standard care for treating diabetic foot ulcers:

• Offloading.

• Control of foot infection.

• Control of ischaemia.

• Wound debridement.

• Wound dressings.

Offer non-removable casting to offload plantar neuropathic, non-ischaemic, uninfected forefoot and midfoot diabetic ulcers. Offer an alternative offloading device until casting can be provided. In line with the NICE guideline on pressure ulcers, use pressure-redistributing devices and strategies to minimise the risk of pressure ulcers developing. When treating diabetic foot ulcers, debridement in the community should only be done by healthcare professionals with the relevant training and skills, continuing the care described in the person's treatment plan.

Consider negative pressure wound therapy after surgical debridement for diabetic foot ulcers, on the advice of the multidisciplinary foot care service. When deciding about wound dressings and offloading when treating diabetic foot ulcers, take into account the clinical assessment of the wound and the person's preference, and use devices and dressings with the lowest acquisition cost appropriate to the clinical circumstances. Consider dermal or skin substitutes as an adjunct to standard care when treating diabetic foot ulcers, only when healing has not progressed and on the advice of the multidisciplinary foot care service.

Do not offer the following to treat diabetic foot ulcers, unless as part of a clinical trial:

• Electrical stimulation therapy, autologous platelet-rich plasma gel, regenerative wound matrices and dalteparin.

• Growth factors: granulocyte colony-stimulating factor (G-CSF), platelet-derived growth factor (PDGF), epidermal growth factor (EGF) and transforming growth factor beta (TGF-β).

• Hyperbaric oxygen therapy.

When deciding the frequency of follow-up as part of the treatment plan, take into account the overall health of the person with diabetes, how healing has progressed and any deterioration. Ensure that the frequency of monitoring set out in the person's individualised treatment plan is maintained whether the person with diabetes is being treated in hospital or in the community.

3C Patch®⁷

3C Patch® is a single-use medical device that is used as part of wound care for foot ulcers in people with diabetes. 3C Patch® is used in combination with the 3CP centrifuge. Together the device and the centrifuge are referred to as the 3C Patch® system. The system is used to make an individual, biological patch from a person's own blood. The patch is a disc-shaped layered matrix of fibrin, leukocytes and platelets and acts as a concentrated source of cells, growth factors and signalling molecules, which are thought to promote wound healing.

3C Patch® is not recommended by the National Institute for Health and Care Excellence (NICE) as a cost-saving option for diabetic foot ulcers.

Diabetic foot infection²

If a diabetic foot infection is suspected and a wound is present, send a soft tissue or bone sample from the base of the debrided wound for microbiological examination. If this cannot be obtained, take a deep swab because it may provide useful information on the choice of antibiotic treatment.

Consider an X-ray of the person's affected foot (or feet) to determine the extent of the diabetic foot problem. Think about osteomyelitis if the person with diabetes has a local infection, a deep foot wound or a chronic foot wound. Osteomyelitis may be present in a person with diabetes despite normal inflammatory markers, X-rays or probe-to-bone testing.
If osteomyelitis is suspected in a person with diabetes but is not confirmed by initial X-ray, consider an MRI to confirm the diagnosis.

All hospital, primary care and community settings should have antibiotic guidelines, covering the care pathway for managing diabetic foot infections, that take into account local patterns of resistance. Do not offer antibiotics to prevent diabetic foot infections.

Start antibiotic treatment for suspected diabetic foot infection as soon as possible. Take cultures and samples before, or as close as possible to, the start of antibiotic treatment. Choose the antibiotic treatment based on the severity of the diabetic foot infection, the care setting and the person's preferences, clinical situation and medical history. Decide the targeted antibiotic regimen for diabetic foot infections, based on the clinical response to antibiotics and the results of the microbiological examination. Do not offer tigecycline to treat diabetic foot infections unless other antibiotics are not suitable.

For mild diabetic foot infections, initially offer oral antibiotics with activity against Gram-positive organisms. Do not use prolonged antibiotic treatment (more than 14 days) for the treatment of mild soft tissue diabetic foot infections. For moderate and severe diabetic foot infections, initially offer antibiotics with activity against Gram-positive and Gram-negative organisms, including anaerobic bacteria, as follows:

• Moderate infections: base the route of administration on the clinical situation and the choice of antibiotic.

• Severe infections: start with intravenous antibiotics and then reassess, based on the clinical situation.

Offer prolonged antibiotic treatment (usually six weeks) to people with diabetes and osteomyelitis, according to local protocols.

Treatment of painful neuropathy

See also the separate Neuropathic Pain and its Management article.

• Provide emotional support for the depressing and disabling nature of the condition.

• Consider initially:
  

  • Bed foot cradles for problems at night.

  • Simple analgesia taken in advance of diurnal symptoms.

  • Contact dressings.

• Consider therapeutic trials of:⁴
  

  • Tricyclic antidepressants (TCAs), which should be used as first-line therapy in painful diabetic neuropathy.

  • Carbamazepine, which is also effective.

  • Gabapentin, which is also recommended in painful diabetic neuropathy and is associated with fewer side-effects than TCAs and older anticonvulsants.

  • Topical capsaicin, which should be considered for the relief of localised neuropathic pain.

Prognosis

Mortality rates after diabetic foot ulceration and amputation are high, with up to 70% of people dying within five years of having an amputation and around 50% dying within five years of developing a diabetic foot ulcer. This high mortality rate is believed to be associated with cardiovascular disease, and emphasises the importance of good diabetic and cardiovascular risk management.²

• Foot ulcers in people with diabetes have a high risk of necessitating amputation.

• Ulcer recurrence rates are high; however, appropriate education for patients, regular surveillance, the provision of post-healing footwear and regular foot care can reduce rates of re-ulceration.

• Early detection and effective management of diabetic foot ulcers can reduce complications, including preventable amputations and possible mortality.⁸

• Even when healed, diabetic foot should be regarded as a lifelong condition and treated accordingly to prevent recurrence.⁹

• Long-term efforts have reduced amputation rates by 37-75% in different European countries over 10-15 years.⁹

• Survival after amputation is poor. Peri-operative mortality is 10-15% in the UK.