The estimated number of people over 16 years of age with diabetes was reported to be 3.1 million in 2010 with a projected rise to 4.6 million by 2030 (Holman et al, 2011). It is likely that diabetes-related complications will also increase rapidly to about 20–30% above present levels by 2045 (Bagust et al, 2002). Consequently, the cost of health care for people with type 2 diabetes may rise by up to 25% during this period; however, with a potentially smaller proportion of active and working age groups, the possible economic burden could be expected to increase by 40–50% (Bagust et al, 2002).
The latest statistics from Diabetes UK (2010) suggest that each year around one in 20 people with diabetes will develop a foot ulcer in 1 year and more than one in 10 foot ulcers result in the amputation of a foot or a leg.
Together with increasing longevity and other comorbidities, it is inevitable that the risk of foot-related problems will not only increase significantly, but also foot problems will become more complex in their presentation and management.
The awareness of diabetic foot complications and the potential devastating impact to patients their families, together with the health economy, has been steadily increasing over the past few years. This is, in part, due to an increase in foot presentations at educational events and published articles, but perhaps also a result of the drive for QOF indicators which included regular diabetic foot examinations (Gadsby and Chadwick, 2011). New and modified diabetic foot QOF indicators now include foot ulcer risk stratification and were introduced on 1 April 2011 (Box 1). Although this is a step in the right direction, some feel that an indicator to encourage the referral of any people found to be at risk of diabetic foot disease should also be introduced (Gadsby and Chadwick, 2011). Screening and risk stratifying will now occur nationwide in GP practices but there is no remuneration via QOF for initiating interventions or making referrals.
The foundations of good foot care in people with diabetes involve adequate monitoring and the opportunity to reinforce messages of self-care and daily foot examination (Boulton and Malik, 1998). There are some data to suggest that many older people with diabetes are unable to perform this daily task due to poor eyesight and reduced mobility, making it difficult to inspect their feet (Thomson and Masson, 1992). Regular contact between professionals and patients is important (Edmonds et al, 1996). Furthermore, in today’s changing healthcare system, targeted and appropriate use of resources, including skilled clinicians, is essential.
Regular examination of the diabetic foot by a suitably trained professional should include:
- Examination of the feet, including assessment of foot sensation using a 10 g monofilament or tuning fork, palpation of foot pulses, inspection of any foot deformity and inspection of footwear (NICE, 2004).
- Identification of any factors predisposing to foot complications to enable education and, if appropriate, intervention to be given to prevent such problems. It is an invaluable time to give advice.
- Identification of pre-existing complications that may require treatment.
- Emphasis of the importance of foot examination and teach the patient how to examine their own feet.
- Identification of more general medical problems, for example the presence of peripheral arterial disease (PAD) would indicate more general vascular pathology.
The reasons for the increased risk to feet in people with diabetes are complex but include neuropathy and PAD as well as more controversial areas such as increased susceptibility to infection.
The rationale for diabetic foot screening is to identify individuals with risk factors for ulceration or amputation and to initiate directed levels of care and education. There appears to be very little robust UK data supporting this approach, however two recent systematic reviews examined risk stratification for foot ulceration. Both concluded that due to small numbers, poor design and data quality, firm conclusions could not be drawn (Arad et al, 2011; Monteiro-Soares et al, 2011). However, evidence from a large Scottish population-based study suggests that risk stratification is highly effective in identifying and reducing foot ulceration (Leese et al, 2006).
If success is to be achieved, a structured and standardised foot screening model should be adopted consisting of:
- Checking for sensory loss.
- Checking for foot pulses.
- Soft tissue examination.
- Identifying previous ulceration or amputation.
- Ascertaining each person’s attitude to and knowledge of foot health and their ulceration risk status.
- Explaining that a basic foot screening examination should account for loss of protective sensation, presence of diabetic painful neuropathy, absent foot pulses, deformity, callus and dry skin, infection, current or previous ulceration, previous amputation, ability to bend to look at their feet, poor vision and finally attitudes, beliefs and knowledge towards foot health.
All of these findings should be recorded in a clear, concise and structured manner with any proposed interventions clearly outlined.
Physically examining feet in people with diabetes gives them a clear message that feet are important and it is imperative to explain what you are doing and why. Equally, at each subsequent visit it is useful to ask the individual why you are examining their feet and if they have any concerns.
Clinical screening tests
There are two commonly used methods for detecting sensory loss associated with foot ulcer risk in clinical practice: the 10 g monofilament and vibration perception using a 128 Hz tuning fork. The most widely used and reported is the 10 g monofilament (Mayfield and Sugarman, 2000; Miranda-Palma et al, 2005). This device is widely available, relatively cheap and reliable, with very little training or expertise required.&
Using either a 10 g monofilament or a 128 Hz tuning fork are not without their limitations or pitfalls. Most of these are related to operator error or poor technique, such as hitting the tuning fork hard so that it can be easily heard and alerts the recipient that the test is imminent, so a positive response is very likely. Asking a patient if they can feel the applied tuning fork is equally misleading as they may feel pressure, cold or vibration. A 10 g monofilament that is jabbed against the skin or wriggled will evoke coarse light touch or even pain receptors and give false positives. It is important, therefore, to be very precise in sensory testing tool methodology.
The 10 g monofilament
The 10 g monofilament was originally invented for testing for sensory loss in the hands of people with leprosy and was not made from nylon but horse hairs. Monofilaments are easy to use but there are some potential areas for incorrect use or misuse. It is important to know that not all available 10 g monofilaments deliver a 10 g force. One study suggests that those manufactured by Bailey Instruments and Owen Mumford are the most accurate devices (Booth and Young, 2000).
Which are the best sites?
The evidence is unclear regarding the number and locations of sites that are required to reliably determine foot ulcer risk status, with the literature citing between one and 14 sites per foot (Baker et al, 2005a). It is clear, however, that inability to detect light pressure stimulus is strongly associated with ulcer risk (Birke and Rolfsen, 1998; Perkins et al, 2001). International guidelines suggest the plantar surfaces of the first toe, first and fifth metatarsal heads as appropriate testing sites (International Working Group on the Diabetic Foot, 2011). It must be remembered that any callused, indurated or scarred areas should be avoided
By nature, peripheral sensory neuropathy originates distally, therefore the author suggests monofilament testing at the plantar surface of the first, third and fifth toe tips (Figure 1). Testing the heel or arch does not add any information to the screening data and, therefore, is unnecessary. If the monofilament is not detected even at one site it is safe to assume that there is a loss of sensory perception.
Monofilaments should be allowed to rest after 10 applications, renewed regularly (the author suggests every 6 months as a rough guide), stored with the monofilament straight and not be placed on hot surfaces.
How to use a 10 g monofilament
- Upon initial use or after rest it is best to buckle the monofilament a few times prior to applying to the person’s skin as this will remove any residual stiffness. If this is not done the monofilament will deliver more than 10 g of force.
- Explain what are you going to do and why. Then apply the monofilament to somewhere else on the person, for example the forearm, so that they can experience the sensation of the monofilament.
- Ask the person to close their eyes and to say “yes” every time they feel the monofilament.
- Apply the monofilament to the tips of the first, third, and fifth toes on the weight-bearing surface of each foot in any order.
- Record their ability to detect the light pressure of the monofilament.
- Re-check any sites that do not invoke a response.
- The monofilament must be placed at 90 degrees to the skin surface.
- It is applied, held and released in a controlled manner.
- It should be applied, held and released over 1–2 seconds for each test.
- When applied and held the monofilament should buckle at about 1 cm from the horizontal.
- It must not “wiggle” or slide when held in place.
Inability to detect one or more sites in each foot indicates sensory deficit and increased ulcer risk.
How to use a tuning fork
Hold the tuning fork by gripping the flat ridged area at the base of the tuning fork with your thumb and forefinger. With your thumb and forefinger press the limbs of the tuning fork together at its tip. Then pull your thumb and forefinger away sharply and let the limbs resonate.&
Place the tuning fork on a bony area away from the foot, such as, the elbow, so the individual can identify the sensation of the vibrating tuning fork. Repeat this process but now place the tuning fork plate on the tip of the individual’s big toe and ask what they can feel. There is little need to test anywhere else for the same reason outlined for 10 g monofilament use.
Note that the person’s eyes are closed during this procedure. Do not ask “can you feel anything?” as they may feel pressure, cold or vibration. It is vibration sense you are testing for.
Defining foot deformity in the context of foot ulcer risk screening should be as simple as possible and should not focus on particular conditions, such as hallux valgus. A simple working definition of deformity is the inability for a foot to be adequately accommodated in a high-street shoe. The importance of this is that an individual with neuropathy will not be able to detect the trauma for an inadequate shoe rubbing over a prominent area.
Skin and nail care
The presence of callus over weight-bearing areas of the foot in the presence of diabetic peripheral neuropathy (DPN) is a very high risk factor for ulceration, increasing risk by up to 77 times (Murray et al, 1996). The presence of bloodstained callus and DPN is highly predictive of ulceration being present in up to 80% of cases following callus removal (Rosen et al, 1985; Harkless and Dennis, 1987).
Additionally, the presence of dry skin may also increase ulcer risk as it is unable to absorb frictional and shear forces that occur during gait. Dry skin is very common in people with DPN because of reduced or absent sweating due to autonomic dysfunction or due to PAD. The daily use of urea- or glycerine-based moisturisers helps to overcome this (Loden, 1996; Miettinen et al, 1999; Baker and Rayman, 2008). Dry skin around the heels is particularly problematic and frequently leads to fissures and possible ulceration and infection.
Good nail care in people with DPN and especially PAD is essential and can be managed by carers if the nails are normal provided that clear advice is given and understood. Thickened nails should be thinned down regularly to prevent pressure sore in the nail bed.
Blisters are caused by frictional forces and, usually, identifying and removing the cause will prevent further injury. As a rule of thumb, if the blister is very tense it should be drained, otherwise covered firmly with a thin gauze dressing and monitored. Most blisters should resolve with basic woundcare without developing to ulceration provided that the cause is identified and removed. However, if there is little sign of healing within 3–5 days, referral to a specialist diabetic foot clinic should be considered.
Infections must be identified and addressed swiftly, taking a microbiological sample, antibiotics and ideally daily reviews for the first 3 days to determine a positive response to treatment. All infections must be treated very swiftly and this is an important role within primary care. Regular review of the individual’s response to antimicrobial therapy is paramount and as a guide, any infection that shows no signs of resolving with 3–5 days should be referred to the specialist foot clinic as a matter of urgency (ideally a same-day referral). A non-resolving infection should be considered for admission with intravenous antibiotics if the specialist foot clinic is not available, such as at weekends or bank holidays.
A recently published NICE (2011) guideline on the inpatient management of the diabetic foot recommends treating the infection according to local guidelines, beginning with oral antibiotics that work against gram-positive organisms for mild infections.
Fungal infections of the skin must also be treated in a similar way as secondary bacterial infection is not uncommon. It is not imperative to treat fungal nail infections.
Peripheral vascular assessment
PAD is characterised by the deposition of atheroma on the intimal lining of lower limb arteries leading to a significant reduction in blood flow and tissue vitality. Screening for the presence of significant arterial disease can be confusing and difficult. In people with diabetes, for every 1% increase in HbA1c there is a corresponding 26% increased risk of PAD (Selvin et al, 2004; Muntner et al, 2005). It is suggested to be concomitant with DPN and is the most likely cause of diabetes-related lower extremity amputations in the developed world (Chaturvedi, 2006). It also frequently co-exists in approximately 45% of people with neuropathic foot ulcers (LeMaster and Reiber, 2006).
The distribution of arterial occlusive lesions is commonly described as multi-segmental, affecting the femoral arteries and tibio-peroneal trunk and crural arteries. Interestingly, the foot vessels are very often spared. Aneurysms of the aorta, iliac and popliteal arteries are not uncommon and can often be felt as a wide very pulsatile artery mass.
Palpating foot arteries
The most commonly used and accepted method for determining the possibility of PAD is by palpation of the pedal pulses. The two significant arteries entering the foot are the dorsalis pedis and posterior tibial vessels. It is not uncommon for the dorsalis pedis artery to be misplaced anatomically or absent. Inability to detect both of these in either foot may signify PAD (Norgren et al, 2007). A very common cause for the inability to palpate pedal pulses is the presence of marked lower limb oedema, which can also mask the true character of Doppler signals. So if the skin looks healthy, pink and is warm, PAD is unlikely to be present.
It is useful to feel the individual’s radial pulse, or your own, when examining foot pulses to ensure that it is not your own finger pulse you are feeling. This is especially true when clinical presentation leads you to suspect PAD. The clinical signs and symptoms of PAD are discussed more fully by Baker et al (2005b) but a summary is given below.
In addition to pulse palpation, some clinical features and symptoms that may help in screening for PAD include the presence of:
- Thin, hard, glassy callus.
- Very dry skin.
- Thin atrophic or thickened dystrophic nails with dark red or very pale nail beds.
- Lesser toes that look like “beef chipolatas”.
- No hair growth in the lower leg or the foot or both.
- A loss of substance to the plantar surface of the foot.
- Pale, sunset red, deep red or purple colouration to the skin.
Do not to forget to ask if the individual suffers from intermittent claudication or rest pain. If they do, then determine how far they can walk before claudication, the recovery time and level of claudication (foot, calf, thigh or buttock).
Any individual with open or previous ulceration, PAD or history of cardiovascular disease may significantly benefit from anti-platelets and statin therapy (Young et al, 2008). A working group for NICE is currently working on national guidance for PAD, due to be published in 2012
Peripheral sensory neuropathy
DPN is reportedly the most common (approximately 50%) and familiar complication that affects the feet of people with diabetes (Kumar et al, 1994). To clarify the differences between DPN and PAD, Table 1 compares the symptoms of both conditions. Prevalence of neuropathy has been shown to increase with diabetes duration (Kumar et al, 1994). There are a variety of manifestations of diabetic neuropathy but most pertinent to the diabetic foot is DPN.
DPN is a reduction or total inability to determine certain stimuli such as light touch, vibration, hot or cold, and pain, for example a sharp sensation. Its pattern is distal and symmetrical, and is often described as having a glove and stocking distribution pattern, where DPN is characteristically observed affecting the lower limb initially in the forefoot but can extend to the mid-thigh and also the hands to wrist level when nerve damage is severe. Additionally, people sometimes describe pins and needles, numbness in their feet or toes or cold feet even when they are warm to the touch.
The inability to feel protective pain sensations and retract is so reduced or absent that injuries such as burns, cuts, blisters and shoe rubs often go unnoticed until they have deteriorated to ulceration or become infected. It is this loss of pain sensation that has been clearly implicated as a major causal factor in foot ulcer development with up to 85% of amputations preceded by foot ulceration (Pecoraro et al, 1990). Significantly, DPN is implicated in 50–75% of nontraumatic amputations (Vinik et al, 2000), so preventing ulceration is critical. It is the inability to feel stimuli that is associated with ulcer risk and is of paramount importance. Identifying this is a cornerstone of ulcer and amputation prevention.
Although DPN is generally thought to be a reduction or loss of sensory perception, up to 16–26% of people with diabetes can develop painful peripheral neuropathy – the differing rates reflect variation in the criteria used to diagnose neuropathic pain (Daousi et al, 2004; Davies et al, 2006). Paradoxically, it can coexist as painless and painful neuropathy, which is the existence of both sensory loss and some of the symptoms of painful neuropathy. Generally in this situation the painful symptoms are those of burning, electric shock type and stabbing pains. This can be very difficult for patients to accept: “How can I have lost feeling but have so much pain!”.
Painful neuropathy may be divided into acute or chronic form. The acute form commonly occurs following a sudden and significant improvement in glycaemic control, and as the terms suggest it is relatively short-lived and usually resolves in 12 months. The chronic form, however, has no clear aetiological pattern, does not resolve and may become progressive. It is a condition that is considered to be under-reported as individuals are likely to only complain of moderate to severe symptoms. Additionally, it could also be that healthcare professionals may not ask patients if they are experiencing any symptoms. This condition is difficult to diagnose and treat. A simple screening tool has been developed to help healthcare professionals screen for DPN (Malik et al, 2011a). This tool is a very simple and quick questionnaire that can be completed by patients in a few minutes and was designed for use in primary care (Figure 2).
Symptoms of painful neuropathy are varied but commonly described as burning, shooting, electric shocks, stabbing pains, or intense pins and needles. Additionally other forms include hypersensitivity to light touch or an over-exaggerated response to a mild noxious stimulus. These symptoms are frequently described as being worse or more intense at night, but in contrast to critical limb ischaemia, are relieved by exercise. It is important to determine whether painful neuropathy is due to diabetes or other causes, such as cancer, HIV, herpes or alcoholism.
Management of neuropathic pain is complex and NICE (2010) recommends duloxetine first-line at 60 mg per day with upward titration to the maximum tolerated dose of no higher than 120 mg. If duloxetine is contraindicated, oral amitriptyline should be offered at a dose of 10 mg per day with gradual titration to an effective dose or the person’s maximum tolerated dose (no higher than 75 mg per day). Consider referral to a specialist pain service (NICE, 2010).
Screening for foot ulcer risk is important, however it is meaningless if the results are not translated into risk status and then acted upon to provide appropriate interventions where required. A study by Leese et al (2006) showed that, compared with those identified as low risk, ulceration was 83 times more common in people at high risk and six times more common in people at moderate risk. The criteria for these categories are outlined in Table 2.
Suggested care plan
Those people with no risk factors for foot ulceration should be rescreened annually. All those identified with risk factors should be referred to a community foot protection team. Tables 3 and 4 summarise care pathways and appropriate referrals for various diabetic foot conditions. The plan below is based upon the model from Leese et al (2006).
- Low risk (foot health education; encourage safe self foot care; reinforce danger signs and method of emergency service access).
- Moderate risk (repeat specific education; podiatry according to risk need; reinforce danger signs and method of emergency service access; provision of special footwear or insoles if required; regular reviews for new risk factors).
- High-risk (as above, plus more frequent podiatry and reviews by diabetes specialist podiatrists; a direct unhindered access to the specialist multidisciplinary foot team).
- All active foot ulceration should be referred to a multidisciplinary foot team within one working day (24 hours).
Once a person has lost sensation it is futile to continually test for it, however PAD should always be reviewed as this has the greater potential for deterioration.
The International Consensus guidelines (International Working Group on the Diabetic Foot, 2011) and NICE (2004) also describes risk-scoring systems that have very similar criteria for each level of risk, however these are not validated by clinical research. This does not mean they are any less useful or reliable and are worthwhile examining.
Screening and risk stratification for foot ulcer risk in people with diabetes is fairly easy to undertake without the need for extensive training. This is provided that clear guidance is given and there is an integrated care pathway with established education and good communication between primary and secondary care. There is of course a need for clinical governance and ongoing updating of knowledge and skills. This CPD module should be a resource to help facilitate effective diabetic foot screening.
To complete the CPD module, click here.