Diabetic foot ulcers: why do they happen and how are they treated?

In his second article on issues surrounding diabetes, Dr Bobby Huda, consultant in diabetes and metabolism at St Bartholomew’s and Royal London Hospitals, discusses a common complication of diabetes

[DIABETIC FOOT ULCERATION affects between 1-2% of people with diabetes each year and is estimated to take up 1% of the total NHS budget. The lifetime risk of developing a diabetic foot ulcer can be between 10-25%.

An ulceration is defined as a break in the skin. People with diabetes are more likely to have peripheral nerve damage (neuropathy) due to longstanding diabetes and/or peripheral vascular disease. Both complications affect the feet disproportionately due to the relative distance from the heart and spinal cord.

This is defined as the presence of symptoms and/or signs of peripheral nerve dysfunction in people with diabetes after the exclusion of other causes. Other less common causes of peripheral neuropathy include vitamin B12 deficiency, thyroid dysfunction, infections, HIV and trauma.

The person with diabetes may experience numbness or pain in the feet. Pain is typically stabbing, burning, worse at night and is usually bilateral. The distribution of neuropathy is usually in a ‘glove and stocking’ fashion, with the feet being affected primarily. Less common are damage to specific nerves or nerve roots (entrapment neuropathies, mononeuritis multiplex). However, many people with diabetic neuropathy can have no symptoms at all. Early neuropathy can be identified at the diabetes annual review, where the feet are tested for sensation with a 10g monofilament for light touch and vibration with a tuning fork.

Peripheral arterial disease (PAD) is defined as atherosclerotic occlusive disease of the lower extremities. It is associated with an increased risk of lower extremity amputation and cardiovascular, cerebrovascular and renovascular disease. Prevalence in people with diabetes ranges between 20-30% but is higher in the presence of a foot ulcer. The presence of PAD is detected by symptoms (intermittent claudication or rest pain) or signs (absent foot pulses, pallor).

People with a significant foot ulcer invariably have neuropathy and around 50% will have PAD. Ulcers can lead to infection very rapidly, particularly with poor glucose control. Ulcer healing is predicted by a number of factors, including control of infection, optimising blood supply and pressure offloading. Optimising those factors needs careful coordination within a diabetes foot multidisciplinary team. This traditionally includes a diabetologist, a vascular surgeon, an orthopaedic surgeon, podiatrist, microbiologist, and an orthotics specialist, with support from diabetes/vascular specialist nurses.

Care is delivered within a diabetes foot MDT clinic, which is podiatry led but with ready access to the MDT. Most diabetes foot ulcers can be managed with regular outpatient appointments and often ulcer healing can take several months. Admission to hospital is indicated in the presence of significant cellulitis, ischaemia, likely presence of osteomyelitis (bone infection), pain and signs of systemic sepsis or hyperglycaemia.

The presence of neuropathy, ischaemia, poor glucose control and abnormal foot pressures can all lead to increased risk of foot ulceration. The presence of risk factors should be identified in the diabetes annual review, which usually takes place within primary care. Foot examination is one of the eight care processes that is measured in the National Diabetes Audit and GP practices are often incentivised to ensure that is carried out. Identification of risks should lead to basic footcare advice and either signposting or onward referral to a community podiatry team.

Previous foot ulceration, callus build up, abnormal foot architecture, for example in the case of Charcot’s neuroarthropathy – which will be covered in detail in a future issue – can significantly increase the chance of foot ulceration, and referral to orthotics for custom-made, pressure offloading footwear is often needed.

People with diabetes foot ulceration often have poor engagement with healthcare professionals, regularly missing appointments to optimise glucose control and identify complications. There is also an increased prevalence of mental health disorders, including depression. They often self-neglect and seek help late when developing foot ulceration.

Primary care and emergency department healthcare professionals, being non-specialists, are often slow to pick up on the significance of a diabetes foot ulcer and treatment with antibiotics, offloading and referral to a diabetes foot clinic can all be delayed. This is crucial, as a person with poor glucose control, neuropathy and ischaemia, if untreated can progress from a superficial ulceration to a major amputation – above knee or below knee – within a week.

The prognosis for people with diabetes foot ulceration is extremely poor. The risks of amputation are high and can vary between 12% and 87% depending on the degree of ulceration at presentation. Scoring systems such as Wagner or SINBAD can be useful in objectively predicting risk. Mortality is also high and up to 50% at five years after an amputation, which is a worse survival rate than many cancers.

Claims are often made around failure to identify significant diabetes foot ulceration and delay in onward referral to specialists: NICE guidelines (NG19) recommend referral within 24 hours. Hence, claims tend to centre around primary care or emergency departments.

Inappropriate footwear, particularly if mandated by the nature of work, can also give rise to claims if ulceration follows. As people with diabetes foot ulcers invariably have poor glucose control and are often poor engagers, defence will often focus on the inevitability of foot ulceration and amputation regardless of the incident episode. q • To contact Dr Huda call 020 3594 6058 / 07919 924925, email bobby.huda1@nhs.net alternatively visit londondiabetes.com or clevelandcliniclondon.uk