Diabetic foot disease is one of the most common, serious, feared and costly complications of diabetes. Patients with diabetes are at a 15- to 40-fold higher risk of a lower limb amputation than patients without the condition. Eighty per cent of lower limb amputations in diabetes are preceded by the development of a foot ulcer and it is estimated that the annual incidence of lower limb ulceration in patients with diabetes varies between 2.2-7%.¹

International studies and guidelines show that targeted foot care and proper screening of risk cases can result in a reduction in the incidence of foot ulcers in patients with diabetes.^2,3,4,5 According to The National Model of Care for the Diabetic Foot, a patient with diabetes must have their feet examined by a podiatrist or other healthcare professional specialising in diabetes care at least once a year.

Causes of foot complications in diabetes

Persistent high blood glucose levels, poorly controlled over an extended period of time, can have detrimental effects on the feet. The combination of peripheral arterial disease (PAD) and peripheral neuropathy (PN) results in an increased risk of diabetes-related foot problems. 

PAD is a highly prevalent atherosclerotic syndrome that is associated with high mortality and morbidity.⁶ It results in the extremities not receiving sufficient blood supply for normal function. Patients may suffer with pain in the back of the calf when walking, known as intermittent claudication. 

PAD leads to progression of infection, and increases tissue breakdown and insufficient delivery of oxygen, nutrition and antibiotics. All these factors further contribute to a potential foot amputation.⁷ In severe cases of PAD, pain may be present even at rest, limbs may show gangrenous changes or tissue loss; which is known as critical limb ischaemia.

PN refers to a dysfunction in the intricate system that connects the brain to the spinal cord, muscle and skin. The presence of diabetic peripheral neuropathy, even with trivial trauma, is the initiating factor of the development of foot ulceration in patients with diabetes. It has been reported that the risk for diabetic foot ulceration increases by seven-fold in patients with peripheral diabetic neuropathy.⁸

Symptoms include burning, tingling, numbness and reduced sensation, which over time results in irreparable nerve damage. Changes in foot shape, loss of balance, loss of muscle tone in the feet and an increase in the frequency of sores and blisters occur. Furthermore, diabetes reduces the ability of wounds to heal, opening the gate for infection.

Presentation in practice (examples)

Distal bilateral symmetrical neuropathy is the most common type of neuropathy associated with diabetes. As nerve dysfunction increases it progresses from distally to proximally. The general term is ‘glove and stocking neuropathy’. The majority of patients who present with a diabetic foot ulcer are asymptomatic with no history of nerve irregularities. Podiatrists can diagnose the type of ulcer: neuropathic, ischaemic, neuroischaemic, with simple testing during a diabetes assessment.

As the disease progresses, muscle weakness becomes more generalised affecting small muscles in both feet and hands. This muscle wasting can result in altering the normal foot dynamics and pressure distribution. Wasting and atrophy of small muscles in the foot lead to loss of joint stability and the development of foot deformities. Foot deformities may take several forms such as equinus or varus deformity, hammer toes, claw toes or a pes planus foot type. These changes lead to pressure distribution disturbance, increased shear stress and friction, ultimately leading to foot ulceration.⁹

Patients presenting with dry and flaky skin as a consequence of sudomotor dysfunction and unexplained foot oedema, which proved unresponsive to diuretics, are associated with diabetic autonomic neuropathy (DAN). 

Anhydrotic heels with excess friction can cause fissures that can act as a portal for bacteria; left undiagnosed these can result in ulceration.

Toenails become brittle, often leading to fungal infections caused by dermatophytes (Tricophyton rubrum) that feed on keratinocytes. This combined with reduced blood flow stunts nail growth. Hair loss begins to occur on toes, feet and legs, lower extremities become pallor in presentation.

Advice to give to patients on footcare

• Ensure diabetes is controlled to prevent damage to the blood vessels and nerve endings in the feet. Increasing activity levels help to stimulate sufficient blood flow
• Checking feet daily, paying particular attention to in between the toes, heels and areas where you suffer from corns or a build-up of callus. If you are unable to bend down, use a mirror or ask someone to check for you 
• Always check for pebbles or stones in shoes and break down of the heel counter before wearing them 
• Wash feet daily in a basin of lukewarm water. For therapeutic effect one can add a cup of Epsom salts (this should be avoided if fissures are evident in the skin). Ensure to check water temperature with your elbow before submerging the feet. Dry feet thoroughly with a soft towel or kitchen roll as the fibres are smaller and more absorbent
• Diabetes can result in dry and flaky skin. Using an emollient daily that contains urea will maintain the moisture level and flexibility in your skin. Do not apply emollient between the toes as this will increase moisture levels and may result in tinea pedis (athlete’s foot)
• Correct footwear is extremely important to protect and support your feet when walking and carrying out activities: wear a shoe with sufficient cushioning, room around the toebox – particularly for those suffering with bunions, hammer/claw toes – and made of long-lasting materials like leather. Ensure your feet are measured correctly before purchasing.

The HSE supports three structured education programmes that educate and enable their patients to look after their diabetes, X-PERT, DESMOND and CODE. They have been shown to improve people’s diabetes control and knowledge, increase the skills needed to look after diabetes overall, and improve health. Patient education and empowerment play a vital role in patients’ overall management of their condition.

Care in podiatry service

A podiatrist utilises The National Model of Care for the Diabetic Foot, which incorporates the low-, the moderate- and the high-risk patients offering different advice while assessing patient’s risk for developing foot complications. They offer diabetes assessments to each group at least once a year for the low-risk group and as frequently as required for the high-risk or active foot disease patient group.

An examination involves: 

• Assessing for any structural changes
• Assessing skin and nail changes
• Palpation of pulses or checking pulses by using a Doppler
• Assessing temperature gradient
• Cutaneous pressure perception testing using a 10g monofilament
• Vibration perception testing (128Hz tuning fork)
• Assessing signs of diabetic autonomic neuropathy (DAN). 

The prevalence of DAN varies from 1-90% in patients with type 1 diabetes and from 20-73% in patients with type 2 diabetes.¹⁰ Signs and symptoms include gastroparesis, change in gut motility, faecal incontinence, bladder and erectile dysfunction, central dysregulation of breathing, sweating abnormalities and dry, pallor skin. Results from the assessment will allow the podiatrist to categorise the patient into a risk group and treat accordingly. The HSE Model of Care for the Diabetic Foot states that all active foot disease patients should be referred to a specialist podiatrist in a grade 4 hospital service within 24 hours. 

Podiatrists can treat wounds by optimising the local wound environment utilising aseptic techniques, correct dressing application and provide sufficient offloading with the use of padding and if needed, a custom silicone device and wound offloading shoes. 

Temporary offloading is required before the patient is referred on to receive the gold standard of treatment for offloading wounds, a total contact cast. 

Patient compliance and vascular status are key factors to be aware of when considering total contact casting (TCC). Infection and poor vascular supply (TCC restricts blood flow) is a contraindication to TCC. 

Primarily, the goals of offloading wound patients are to reduce tissue motion, accommodate osseous deformities or protrusions, provide maximum shock absorption, and reduce the amount of time the foot is on the ground.¹⁰

Key ‘foot’ messages

If you are working with diabetes patients, whether they are considered to be low risk, medium risk or high risk, ensure you have a podiatry contact that you can refer to when necessary. 

To be able to provide an effective plan for diabetic foot syndrome prevention and treatment, a multidisciplinary team approach is required. A podiatrist offers a vital role by guiding the patient on how to prevent diabetic foot lesions and by providing treatment when they occur. Podiatrists are exposed to an array of foot lesions and diseases on a daily basis and have a wealth of experience on the diagnosis and treatment of such. 

If a patient appears to have poor balance, consider their footwear and the structural shape of their foot. Could they benefit from custom orthotics? Or are they simply wearing incorrect footwear? Patients are often misguided by fashion trends, eg. memory foam shoes which over time will flatten and wear down easily in areas of high pressure. If this is left unnoticed, wearing such shoes can result in a breakdown of tissues and eventual ulceration. 

A custom orthotic with long-lasting materials with the addition of cushioning to areas in shoes that often break down can greatly reduce risk of ulceration.

When and if carrying out diabetes assessments, ensure to always check the feet. Look, compare, palpate, assess. If you are unsure what certain abnormalities in the feet mean, contact a podiatrist.

Regardless of the severity of diabetes, patients should avoid the use of corn plasters at all times. The high content of acid can macerate, irritate and often cause an infection which could have been simply avoided with a routine treatment from a podiatrist.

References

1. Hse.ie. URL: https://www.hse.ie/eng/services/list/2/primarycare/east-coast-diabetes-service/management-of-type-2-diabetes/foot-care/model-of-care-diabetic-foot.pdf 
2. Patout CA, Birke JA, Horswell R, Williams D, Cerise FP. (2000). Effectiveness of a comprehensive diabetes lower extremity amputation prevention program in a predominantly low-income African-American population. Diabetes Care, 2000; 23(9): 1339-42
3. Dargis V, Pantelejeva O, Jonushaite A, Vileikyte L, Boulton AJ. (1999). Benefits of a multidisciplinary approach in the management of recurrent diabetic foot ulceration in Lithuania: a prospective study. Diabetes Care, 1999; 22(9): 1428-31
4. McIntosh A, Peters J, Young R, Hutchinson A, Chiverton R, Clarkson S, Foster A, Gadsby R, O Connor M, Rayman G, Feder G, Home PD. (2003). Prevention and management of foot problems in type 2 diabetes: clinical guidelines and evidence. Sheffield University: Sheffield
5. SIGN Scottish Intercollegiate Guidelines Network. (2010). Management of diabetes, a national clinical guideline. NHS Quality Improvement Scotland
6. Akbari CM, Macsata R, Smith BM, Sidawy AN. Overview of the diabetic foot. Semin Vasc Surg. 2003; 16: 3-11
7. Katsilambros N. Who is the patient at risk for foot ulceration. In: Katsilambros N, Dounis E, Tsapogas P and Tentolouris N Atlas of the diabetic foot, editors. Chichester; Hoboken, NJ: Wiley; 2003; pp: 1-21
8. Reiber GE, Vileikyte L, Boyko EJ, del Aguila M, Smith DG, Lavery LA, Boulton AJ. Causal pathways for incident lower-extremity ulcers in patients with diabetes from two settings. Diabetes Care. 1999;22:157-162
9. Vučković-Rebrina, S., Barada, A. and Smirčić-Duvnjak, L. (2013). Diabetic Autonomic Neuropathy. Diabetologia Croatica,2013; 42(3): p.73
10. Boulton A. Peripheral neuropathy and the diabetic foot. The Foot. 1992; 2: 67-72