Introduction
Diabetic foot ulcerations are a significant complication of diabetes and often precede minor (below the ankle) or major (above or below the knee) amputation. At least 2% of people with diabetes experience new foot ulcers annually, and of these, one in 400 undergoes amputation (Kerr, M. 2019)

Presentation:
Diabetic foot ulcerations are classed as a break in the epithelium below the malleoli. Risk factors for ulceration include neuropathy and peripheral arterial disease.

Neuropathic ulceration
Neuropathy is the common factor with 90% of patients presenting with ulceration demonstrating a degree of loss of protective sensation (Alexiadou, K. Doupis, J. 2012). The loss of feeling associated with diabetic neuropathy results in the inability to feel pain, pressure and heat resulting in patients often being unaware of the presence or severity of the ulceration. Ulceration in the neuropathic foot will tend to be located on areas of pressure such as the plantar aspect of the metatarsals or digits. The foot will be warm and well perfused with palpable pulses.

Ischaemic ulceration
Peripheral arterial disease (PAD) is more common and severe in the diabetic population with PAD 2-8 times more likely in those with diabetes (Alexiadou, K. Doupis, J. 2012). The ischaemic foot will often be cool and hairless with thin shiny skin. Foot pulses will be absent. The patient may report symptoms of intermittent claudication or rest pain. Ulcerations tend to be located around the peripheries of the foot or between the toes.

The majority of foot ulcerations will present with both neuropathy and ischaemia and are classed as neuro-ischaemic ulceration.

Assessment
Assessment of ulceration can help determine the most appropriate treatment

Neuropathy
The National Institute for Health and Care Excellence (NICE 2015) recommends the use of the 10g monofilament to assessment for loss of protective sensation. This nylon thread exerts 10g of pressure to the skin when it bends (fig 1). A patient who is unable to feel this at any site on the foot is deemed to have a loss of protective sensation.



Fig 1. Method and site of application of the 10g monofilament (Boulton, A. Lavery, L. 2008)

An alternative test not requiring an instrument is the Ipswich Touch the Toes test. This test involves touching the tips of the 1st, 3rd and 5th toes on each foot lightly and briefly with the index finger. If the patient is unable to feel two or more areas (this could be two areas on one foot, or one area or more on both) loss of protective sensation is suspected.

Touch the toes test video: https://www.youtube.com/watch?v=KbMljfRubvQ

Peripheral arterial disease
Patient history about standard cardiovascular risk factors including cerebrovascular disease, coronary heart disease and smoking history should be obtained. It is also important to determine if the patient has had any previous vascular interventions (surgical and interventional radiological procedures).

Symptoms of PAD including intermittent claudication and rest pain should be assessed and documented. Intermittent claudication is described as a cramping-like pain commonly occurring in the calves, thighs or buttocks brought on by walking. This is relieved by rest, but reoccurs when the patient starts to walk again. Rest pain is an indication of critical limb ischaemia and occurs when the patient is lying flat. The pain is described as a burning pain and is relieved only by dangling the legs off the edge of the bed. Patients with rest pain often choose to sleep in a seated position to enable them to keep their feet dependent. It is important to note that symptoms of PAD may be masked in patients with peripheral neuropathy.

Observation of the feet for signs of colour change (pale or cyanotic) atrophy of skin or the absence of hair should be undertaken. The temperature of the foot should also be assessed using the back of the hand, with the ischaemic foot often cool to touch particularly at the peripheries. Pulse palpation should include the pedal pulses as a minimum (fig 2) but also popliteal and femoral if possible. Absence of any pedal pulse could suggest PAD.

Femoral
Popliteal
Posterior Tibial
Dorsalis Pedis
Fig 2: Palpation location of femoral, popliteal, posterior tibial and dorsalis pedis pulses (Hill, D.R. Smith, R.B. 1990)

Hand-held Doppler assessment if available can be used to assess wave formation along with ankle-brachial pressure (ABPI) assessment. An ABPI of less than 0.8 is indicative of PAD.

If peripheral arterial disease is suspected, a vascular surgical opinion should be sought.

Ulcer assessment
The size, depth and location of any wound should be assessed and documented. Depth of wound can be assessed using a sterile plastic or metal or alternatively a wound swab. This can be used to determine the true dimensions of the wound. The probe should be used to gently press the edges and base of the wound to locate any undermining edges or deep sinuses. The probe can then be removed and measured to establish the depth of the wound (fig 3)

Fig 3: Using a sterile wound swab to determine the depth of a wound sinus (Cooper, P. 2006)

The appearance of the wound base should also be assessed. Healthy granulation tissue is pink and is indicative of wound healing. The presence of slough (yellow or cream in colour), necrotic tissue (black or grey) or eschar (black, dry hard necrotic tissue) will prevent wound healing and harbour bacteria. This will often require debridement as part of wound management to enable the wound to heal.

Infection:
Diabetic foot infections should be identified clinically based on the local and systemic signs of infection. It is suggested that clinical diagnosis should be based on the presence of two or more signs of inflammation; redness, pain, swelling or purulent secretions (Lipsky, B,A. Aragon-Sanchez, J. 2016). Other signs that may also be present include the presence of necrotic tissue, discoloured granulation tissue and wound malodour. It is important to note that some signs and symptoms of infection will be diminished in the presence of neuropathy or peripheral arterial disease. Diabetic foot infections should be classified using a system such as by the Infectious Disease Society of America (IDSA) or International Working Group for the Diabetic Foot (IWGDF) (Fig 4)

Fig 4: Diabetic foot infection classification system IDSA/ (Wukich, D.K. Armstrong, D.G. 2013)

Tissue samples or deep wound swabs should be obtained (after the wound has been cleansed well with saline) from wounds where soft tissue infection is suspected to help identity causative microorganisms and guide antibiotic treatment.

Gangrene
Both wet and dry gangrene can occur in the diabetic foot as a result of ischaemia, infection or mechanical trauma.

Dry gangrene of the digits (fig 5) without clinical signs of infection can be managed in the community with close monitoring. These digits will often auto-amputate without surgical intervention. A vascular surgical opinion should also be sought to identify if the patient requires revascularisation.

Fig 5: Dry gangrene

Wet gangrene (fig 6) with associated with infection requires urgent medical assessment and admission for IV antibiotics and surgical debridement. A vascular surgical opinion should also be sought to identify if the patient requires revascularisation.

Fig 6: Wet gangrene

Osteomyelitis
The probe to bone test is highly predictive for osteomyelitis in infected foot ulceration (Frykberg, R.G. Wittmayer, B. 2007). This is where the bone is visible or palpable at the base of a wound. In these patient inflammatory markers, in particular erythrocyte sedimentation rate (ESR), will be markedly elevated.

Plain x-rays should be obtained of all non-superficial infected diabetic foot ulcerations to assess for bone involvement (Wukich, D.K. Armstrong, D.G. 2013). It is important to note however that bone changes are more likely to be identified in ulcerations present for more than 3 weeks as there can be a delay of 10 to 20 days before acute changes are seen on x-ray. MRI should be considered as it has a high sensitivity for detecting early osteomyelitis (Lee, Y.J. Sadigh, S. 2016).

The gold standard for diagnosis of osteomyelitis is bone biopsy sample processed for histology and culture (Cavanagh, P.R. Lipsky, B.A. 2005) however this is often impractical. Patients with suspected osteomyelitis should be referred for a surgical opinion.

Management
All diabetic foot ulcerations should be referred to the local Foot Protection team (usually Podiatry) within 24hrs, in accordance with NICE guidance of the management of the diabetic foot (NICE 2015). Some form of wound debridement is likely to be required to encourage wound healing and remove devitalised and infected tissue. This is often undertaken using sharp debridement and should only be performed by a qualified health professional, usually a podiatrist or tissue viability nurse.

Dressings
All wounds should be covered with a simple dry dressing at all times to reduce the risk of further infection. A non-adherent first layer dressing (e.g. Jelonet or Atrauman) is usually recommended to minimise pain and limit damage to the wound bed during dressing changes. A secondary dressing such as sterile gauze is recommended to absorb exudate. The dressing should be changed regularly (every day in heavily exuding wounds) to prevent wound deterioration and enable wound assessment. Dressing advice can be obtained from your local podiatry or tissue viability team.

Offloading
Offloading by reducing mobilisation and redistributing pressure away from the foot ulceration is a key area of ulcer management. During hospitalisation, this can be achieved most effectively with bed rest but there are many devices available to provide protection to the wound while the patient moves around. The cheapest most widely found device is the surgical sandal (fig 7) used with crutches to limit contact of the foot with the ground. These are available with a forefoot cut out (for forefoot ulceration), rearfoot cut out (for ulcerations to the heel) and a flat sole which should be considered in the patient at high risk of falls.

Fig 7: Forefoot cut out, rearfoot cut out and flat-soled surgical sandal

The gold standard treatment is the total contact cast which should be applied by an experienced plaster technician or podiatrist. This should be considered in the absence of peripheral arterial disease in patients with ulcerations to the plantar aspect of the foot.

Involvement of physiotherapy and occupational therapy teams is recommended during admission for assessment of patients ability to non-weight bear and suitability for offloading devices. Therapy teams should also be involved in discharge planning to ensure offloading can be achieved in the patients home environment.

Antibiotic treatment 
Hospitalisation is rarely required for mild infections and these can usually be managed with oral antibiotics and regular wound dressings in the community by local podiatry teams. Moderate infections occasionally require admission, usually when the infection has not responded to outpatient treatment or is accompanied by PAD. Patients with severe infection presenting with systemic signs should always be hospitalised. A broad-spectrum empiric regimen is recommended for initial management before narrowing coverage once wound swab/deep tissue sample culture results are obtained. Discussion with microbiology regarding most suitable antibiotic regimes is also recommended.

Glycaemic control
Optimisation of diabetes control in order to aid wound healing is important and referral to the local Diabetes team during inpatient admission recommended. An HbA1c can assess their recent glycaemic control. Do bear in mind that infection can cause hyperglycaemia, therefore as they get better they may need to reduce their antihyperglycaemic agents.

Surgical opinion 
Patients presenting with moderate or severe infection of diabetic foot ulcerations may require surgical removal of devitalised soft tissue and bone, or drainage of collections in theatre. Teams undertaking this type of procedure should have experience in performing limb preservation procedures. Patients presenting with peripheral arterial disease should be assessed for opinion for revascularisation as soon as any major infection has been adequately addressed (Wukich, D.K. Armstrong, D.G. 2013)

Psychological factors
Some of these patients may have underlying psychosocial factors that reduce their abilities to engage with treatment - these need to be explored & addressed. These factors otherwise may result in repeated admissions when ulcers deteriorate on discharge. Furthermore, patient health beliefs have been demonstrated to have an impact on their adherence to good foot care practices (Vedara et al 2014) Finally, there is some evidence to suggest that increased stress levels can negatively impact of wound healing (Ebrecht et al 2004). Referral to psychology services for should, therefore, be considered for assessment.

Discharge education and planning
Careful discharge planning should be undertaken to minimise the risk of patients being readmitted with deteriorating or reoccurring wounds.

Patients with active foot ulceration should be referred on discharge to the local Foot Protection team, which in most Trusts will be the local podiatry service, either directly or via the GP (NICE 2015). Podiatry review should be arranged within a few days of discharge to ensure that discharge plans are being implemented in regards to wound dressing and offloading.

Patients should be advised to keep wounds covered and dressings dry. Offloading advice should be re-iterated to ensure that patients are clear about when and how offloading devices should be used. Patient education should also be considered, providing advice to patients and their carers about how they can best manage their diabetes and feet at home, and where and when to seek help. 

Do provide patients with this helpful leaflet from Diabetes UK: Simple Steps to Healthy Feet Patient information leaflet

Further reading and references
Alexiadou, K. Doupis, J. (2012) Management of Diabetic Foot ulcers. Diabetes Therapy, Vol 3(4) p.p. 1-15

Boulton. A.J.M. Armstrong, Lavery, L.A. Armstrong, D.G. LeMaster, J.W. Albert, S.F. Mills, J.L. Frykberg, R.G. Mueleer, M.J. Hellman, R. Sheehan, P. Kirkman, M.S.Wukich, d.K. (2008) Comprehensive foot examination and risk assessment: A report of the task force of the Foot Care Interest Group of the American Diabetes Association, with endorsement by the American Association of Clinical Endocrinologists. Diabetes Care, Vol 31(8) p.p. 1679-1685

Cavanagh, P.R. Lipsky, B.A. Bradbury, A.W, Botek, G. (2005)Treatment for diabetic foot ulcers. Lancet, Vol 366, p.p.1725-1735

Chandra Misra, S. Chharbar, K. Kashikar, A. Mehndiratta, A. (2017) Diabetic foot. The British Journal of Medicine. Vol 359, suppl 1. p.p. 1-7

Cooper, P. (2006) How to probe a wound during assessment to help determine treatment options. Wound Essentials Vol 1, p.p. 87-89

Ebrecht, M. Hextall, J. Kirtley, L.G. Taylor, A. Dyson, M. Weinman, J. (2004) Perceived stress and cortisol levels predict speed of wound healing in healthy male adults. Psychoneuroendocrinology, 29 (6), p.p.798-809

Edmonds, M. Foster, A. (2006) ABC of wound healing. Diabetic foot ulcers. The British Journal of Medicine. Vol 332, p.p 407-410

Frykberg, R.G. Wittmayer, B. Zgonis, T. (2007) Surgical Management of diabetic foot infections and osteomyelitis. Clinics in Podiatric Medicine and Surgery. Vol 24, p.p. 469-482

Grey, J. Enoch, s. Harding, K. (2006) ABC of wound healing. Wound Assessment. The British Journal of Medicine. Vol 332, p.p. 285-288

Hill, D.R. and Smith, R.B. (1990) Clinical Methods: The history, physical and laboratory examinations. 3rd edn. Boston: Butterworths

Ince, P. Abbas, Z. Lutale, J. Basit, A. Mansoor, S. Chohan, R. Morbach, s. Mollenbery, J. Game, F.L. Jeffcoate, W. (2008) Use of the SINBAD Classification System and Score in comparing Outcome of foot Ulcer Management on Three Continents. Diabetes Care, Vol 31, p.p. 964-967

Jeffcoate, W.J. Harding, K.G. (2003) Diabetic foot ulcers. The Lancet. Vol 361, p.p1545-1551

Jude, E. Gibbons, J. (2005) Identifying and treating intermittent claudication in people with diabetes. The Diabetic Foot. Vol 8, p.p. 84-92

Kerr, M. Barron, E. Chadwick, P. Evans, T. Kong, W.M. Rayman, G. Sutton Smith, M. Todd, g. Young, B. Jeffcoate, W.J. (2019) The cost of diabetic foot ulcers and amputations to the National Health Service. Diabetic Medicine, Vol 36, p.p. 995-1002

Lee, Y.J. Sadigh, S. Mankad, K. Kapse, N. Rajeswaran, G. (2016) The Imaging of Osteomyelitis. Quantitative Imaging in Medicine and Surgery, Vol 6(2), p.p. 184-198

Lipsky, B,A. Aragon-Sanchez, J. Diggle, M. Embil, J. Lavery, L. Senneville, E. Urbancic-Rovan, V. Can Asten, S. Peters, E.J.G. (2016) IWGDF guidance of the diagnosis and management of foot infections in persons with diabetes. Diabetes/Metabolism Research and Reviews. Vol32(Supple. 1) p.p.45-74

National Institute for Health and Care Excellence (2015) NG19 Diabetic foot problems: prevention and management. Available at https://www.nice.org.uk/guidance/ng19 (accessed: July 2020)

Vedhara, K. Dawe, K. Wetherell, M.A. Milds, J.N.V. Cullum, N. Dayan, C. Drake, N. Price, P. Tarlton, J. Weinman, J. Day, A. Campbell, R. (2014) Illness beliefs predict self care behaviours in patients with diabetic foot ulcers: A prospective study. Diabetes Research and Clinical Practice, Vol 106, p.p.67-72

Wu, S.C. Driver, V.R. Wrobel, J.S. Armstrong, D.G. (2007) Foot Ulcers in the diabetic patient, prevention and treatment. Vascular Health and Risk Management. Vol 3(1), p.p.65-76

Wukich, D.K. Armstrong, D.G. Attinger, C.E. Boulton, A.J.M. Burns, P.R. Frykbert, R.G. Hellman. R. Kim, P.J. Lipsky, B.A. Pile, J.C. Pinzur, M.S. Siminerio, L. (2013) Inpatient Management of diabetic Foot disorders. A Clinical Guide. Diabetes Care. Vol 36, p.p. 2862-2871

Written by Debbie Coleman (Diabetic Foot Co-ordinator & Podiatrist)