The Diabetic Foot

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

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, which further impairs the ability to sustain pressure.
• Motor fibre abnormalities lead to undue physical stress, 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 or life-threatening.
• Detection and surveillance of diabetic neuropathy are an essential routine part of a diabetic annual review (see Managing Diabetes in General Practice).

• 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), and 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.

• The Charcot foot is characterised by bone and joint degeneration which can lead to a devastating deformity. Usually presents after minor trauma as a hot swollen foot.
• 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 and realignment arthrodesis of the hind foot can sometime prevent amputation.¹

• The results of cross-sectional community surveys in the UK showed that 5.3% (type 2) and 7.4% (type 1 and 2 combined) of people with diabetes had a history of active or previous foot ulcer.
• An annual incidence of 2.2% was found in a large community survey in UK, and up to 7.2% in patients with neuropathy.
• The incidence of major amputation is between 0.5 and 5.0 per 1000 people with diabetes.

• Ensure optimum control of diabetes, including glucose, blood pressure and lipids, for all patients with Type 1 diabetes and Type 2 diabetes.
• Don't delay: deterioration in an ulcer is more likely if assessment and management is delayed.²
• Patients with clinically significant peripheral vascular disease and limb ischaemia should be assessed by a vascular surgeon to determine the need for angioplasty, stenting, or femoro-distal bypass. Since ischaemia can delay healing, revascularisation needs to be considered at an early stage.³
• Antimicrobial therapy should be guided by culture results, and should aim to cure the infection, not to heal the wound.
• Alleviation of the mechanical load on ulcers:
  • Neuropathic ulcers typically heal in 6 weeks with total contact casting, because it effectively relieves pressure at the ulcer site and enforces patient compliance.⁴
  • The success of other approaches to off-loading also depends on the patients' adherence to the effectiveness of pressure relief.
• Surgery to heal ulcers and prevent recurrence can include tenotomy, tendon lengthening, reconstruction, or removal of bony prominences. However, these procedures may result in secondary ulceration and other complications.

• Effective care involves a partnership between patients and professionals, and all decision making should be shared.
• Organize 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.
• 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
  • Classify foot risk as (if patient has had previous foot ulcer or deformity or skin changes manage as high risk):
    • Low current risk
    • Increased risk
    • High risk
    • Ulcerated foot
• Care of people at low current risk of foot ulcers (normal sensation, palpable pulses):
  • Agree a management plan including foot care education with each person
• Care of people at increased risk of foot ulcers (neuropathy or absent pulses or other risk factor):
  • Arrange regular review, 3-6 monthly, by foot protection team.
  • At each review:
    • Inspect patient's feet
    • Consider need for vascular assessment
    • Evaluate footwear
    • Enhance foot care education
• Care of people at high risk of foot ulcers (neuropathy or absent pulses plus deformity or skin changes or previous ulcer):
  • Arrange frequent review (1-3 monthly) by foot protection team.
  • At each review:
    • Inspect patient's feet
    • Consider need for vascular assessment
    • Evaluate and ensure the appropriate provision of:
      • Intensified foot care education
      • Specialist footwear and insoles
      • Skin and nail care
    • Ensure special arrangements for those people with disabilities or immobility
• Care of people with foot care emergencies and foot ulcers
• Foot care emergency (new ulceration, swelling, discolouration):
  • Refer to multidisciplinary foot care team within 24 hours. The core specialist foot care team should usually consist of a specialist podiatrists, specialist orthotists, nurses with training in the dressing of diabetic foot wounds and diabetologists with expertise in diabetic lower limb complications.
• Expect that team, as a minimum, to:
  • Investigate and treat vascular insufficiency.
  • Initiate and supervise wound management.
  • Use dressings and debridement as indicated.
  • Use systemic antibiotic therapy for cellulitis or bone infection as indicated.
  • Ensure an effective means of distributing foot pressures, including specialist footwear, orthotics and casts.
  • Try to achieve optimal glucose levels and control of risk factors for cardiovascular disease.

• Provide emotional support for the depressing and disabling nature of the condition
• Consider initially:
  • Bed foot cradles for night-time problems
  • Simple analgesia taken in advance of diurnal symptoms
  • Contact dressings
• Consider therapeutic trials of:³
  • Tricyclic antidepressants (TCAs) should be used as first line therapy in painful diabetic neuropathy.
  • Carbamazepine is also effective.
  • Gabapentin is also recommended in painful diabetic neuropathy and is associated with fewer side effects than TCAs and older anticonvulsants.
  • Topical capsaicin should be considered for the relief of localised neuropathic pain.

Foot ulcer

• Is usually painless, punched-out ulcer in an area of thick callus ± superadded infection, pus, oedema, erythema, crepitus, mal-odour.
• Involve your local diabetes foot team without delay. A well-organised multidisciplinary approach providing continuity of care between primary and secondary care is essential.⁴
• If there is cellulitis or bone infection, admission is essential for intravenous antibiotics, often starting with benzylpenicillin and flucloxacillin and then adjusting when microbiology results are known.
• Use local measures including:
  • Debridement and trimming of callus
  • Dressings to absorb exudate
  • Bed rest and foot casts to relieve pressure
  • Surgical drainage
• Systemic and proximal measures including:
  • Intravenous or oral antibiotic therapy: usually staphylococcal coverage, plus wider spectrum, anaerobes, or streptococcal as specifically indicated.
  • Vascular referral, investigation, and reconstruction or angioplasty if indicated.
• Involve surgeons early: the degree of peripheral vascular disease, the patient's general health and the patient's age, lifestyle and views will determine whether local excision and drainage, vascular reconstruction and/or amputation (and how much) is appropriate.
• Absolute indications for surgery:
  • Abscess or deep infection
  • Spreading anaerobic infection
  • Severe ischaemia or rest pain
  • Septic arthritis
• Amputation is generally reserved for:
  • Uncontrolled pain (secondary to vascular disease)
  • Debilitating, long-term, non-healing ulceration
  • A useless and disabling infected or Charcot foot

High risk foot (neuropathy or vascular disease or previous ulcer)

Involve the local specialist diabetes foot care team and provide:

• Regular foot assessment (1-3 monthly) - make special arrangements if immobile or disabled
• Local preventative attention to callus
• Relief of pressure using foam spacers, made-to-order shoes, customized insoles
• Regular foot care education
• Vascular referral if symptoms or critical arterial supply

At risk foot (deformity or self-care problem or simple skin problem)

Provide:

• Routine foot care according to need
• Advice on appropriate footwear - never bare feet!
• Foot care education at routine visits
• Advice to carers

• Ulcer recurrence rates are high, but appropriate education for patients, regular surveillance, the provision of post-healing footwear and regular foot care can reduce rates of re-ulceration.
• Survival after amputation is poor. Perioperative mortality is 10-15% in the UK.²