Neuropathic Foot

• Foot complications of diabetes are common and include arterial insufficiency and peripheral neuropathy, which can readily lead to ulceration

• Foot ulcers may be associated with deep infection and put the patient at risk of osteomyelitis and systemic sepsis

• Maintaining foot health demands a proactive approach involving regular checks and patient education, which should be part of routine surveillance

• Development of an 'at risk' foot justifies more frequent assessment

• Conservative measures include removal of callus, desloughing, pressure relief casts, surgical debridement, abscess drainage, and revascularisation

• Local care pathways for managing foot complications should be well understood to ensure prompt action and reduce the need for amputation

Introduction

Foot complications are a serious threat to patients with diabetes (Figure 14.1) and must always be treated energetically. Three major factors are vascular disease, peripheral neuropathy and raised risk of infection. These may threaten not only the limb in question but also the life of the individual, and regular surveillance and early intervention (particularly when infection intervenes) are essential. Around 50% of non-traumatic foot amputations are carried out on people with diabetes. Foot problems are perhaps the most preventable complication of diabetes, but require coordinated teamwork, including education of the patient and carers.

The three risk factors Vascular insufficiency

Peripheral vascular disease is often asymptomatic until a well-established stage. Ischaemia reduces the immunological response to infection, delays healing and raises the likelihood of anaerobic infection in the deeper tissues.

Neuropathy

Peripheral neuropathy reduces light touch sensation putting the foot at risk of unnoticed trauma, and also impairs proprioception, leading to deformity and swelling of the joints. These problems can mask deeper foot sepsis, which should always be suspected when apparently superficial infection fails to heal. Neuropathy is extremely common (up to 50% of type 2 patients), but in many of these it produces no symptoms and can only be excluded through physical examination. Autonomic neuropathy is less common, but may cause reduction in sweating with dryness of the skin, promoting fissuring and ulceration.

Infection

Infection may be obvious superficially, or may be deeper, where it can invade bone, form abscesses, promote gangrene and produce systemic sepsis.

''While mild infections are relatively easily treated, moderate infections may be limb threatening, and severe infections may be life threatening"

International Diabetes Federation Consensus Guidelines on the Management and Prevention of the Diabetic Foot, 2003

Ischemia Necroticulcer
Figure 14.1 Necrotic ulcer on the second toe with proximal erythema and swelling (photograph courtesy of Mr G Deogan, University Hospital, Coventry).

Patterns of presentation

Whilst the factors often co-exist, two major patterns are seen (all photographs courtsey of Mr G Deogan, University Hospital, Coventry).

The neuropathic foot

Where neuropathy predominates the problems tend to occur at the pressure areas on the plantar surfaces, and ulcers are usually pre-cededby callus formation on the sole. Neuropathic feet (Figures 14.2 and 14.3) are typically warm with easily palpable pulses due to reduction of sympathetic tone on the arteries, but reduced sensation is present on microfilament testing. Distortion and swelling of the joints (Charcot's joints) may be present. Occasionally, severe neuropathy may cause oedema of the feet and lower legs.

The ischaemic or neuro-ischaemic foot

Where arterial insufficiency is the major factor the foot is often cool to touch and pulses are reduced or absent. Hair growth

Figure 14.2 Deep heel ulceration in a neuropathic foot.
Neuropathic Foot

Figure 14.3 Pressure from tight footwear on insensitive toes has caused calluses now ulcerating superficially.

Figure 14.4 Gangrenous ulceration in a neuro-ischaemic foot.

Figure 14.3 Pressure from tight footwear on insensitive toes has caused calluses now ulcerating superficially.

Figure 14.4 Gangrenous ulceration in a neuro-ischaemic foot.

may be reduced although this sign is rather non-specific in older patients. If ischaemia becomes critical, the foot is typically pink and painful and urgent action is then required. Ischaemic ulcers are usually distal and on the margins of the feet rather than the soles (Figure 14.4). They are not necessarily related to callosities, in contrast to purely neuropathic ulcers. But frequently, neuropathy and ischaemia co-exist (the 'neuro-ischaemic foot', Figure 14.4), complicating assessment and this overlap should always be borne in mind.

Regular surveillance

All patients with diabetes should have a thorough foot examination at least annually, and in those with signs of complications or 'at-risk' features this frequency should be increased. The examination should include, as a minimum, the following:

• Inspection of the general health of the feet. Signs of deformity, hair loss, loss of skin integrity, loss of sweating, swelling of joints, callosities, nail health, fungal infection between the toes and in the nails. Deformity or swelling may suggest an underlying Charcot's joint (see Figure 14.6). Callosities suggest abnormal distribution of weight over the sole, which may indicate peripheral neuropathy

• Assessment of vascular sufficiency. Temperature of the skin, detection of dorsalis pedis and posterior tibial pulses, capillary return at the toes

• Assessment of neurological integrity. Light touch sensation using a 10 g nylon microfilament device at all of the 'at risk' areas (see Figure 14.5) and vibration sense at the great toe and ankle. Achilles tendon reflex

Problems identified during a surveillance examination should be actioned accordingly (Boxes 14.1 and 14.2). Ulceration, however small, requires immediate active management. It is estimated that 4-10% of the population with diabetes has a foot ulcer. Eighty-five per cent of foot amputations in people with diabetes occur following the development of an ulcer.

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