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 (see below), 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).

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

Epidemiology¹

• 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.

Aetiology

• 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.

Management^2,3

• Ensure optimum control of diabetes, including glucose, blood pressure and lipids, for all patients with Type 1 diabetes and Type 2 diabetes.
• Foot care emergency (new ulceration, swelling, discolouration):
  • Don't delay: deterioration in an ulcer is more likely if assessment and management is delayed.¹
  • Take swabs and treat with prompt antibiotics - usually staphylococcal coverage, plus wider spectrum, anaerobes, or streptococcal until sensitivities known.
  • Admit patient for systemic antibiotic therapy for significant cellulitis or bone infection. Adjust antimicrobial therapy according to culture results when available.
  • If not admitted as an emergency, refer to multidisciplinary foot care team within 24 hours. A well-organised multidisciplinary approach providing continuity of care between primary and secondary care is essential.⁴
    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. 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.⁵
    • Initiate and supervise wound management .
    • 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 (debridement) and drainage, vascular reconstruction and/or amputation (and how much) is appropriate.
      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.
      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
    • Ensure an effective means of distributing foot pressures (alleviation of the mechanical load on ulcers), e.g. specialist footwear, orthotics and casts.
      • 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.

Prognosis

• 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.¹

• 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.⁶

• 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:⁵
  • 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.

• 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