Legs and Feet
Diabetes affects the lower limb in a large number of people. For a person with diabetes the lifetime risk for developing a foot ulcer is reportedly as high as 25% and it is believed that every 30 seconds somewhere in the world a lower limb is lost as a result of diabetes (1). Peripheral neuropathy combined with micro- and macrovascular disease (that is, disease of both small and large blood vessels) can lead to ulceration, deformity, infection, and ultimately amputation. Lower limb problems are a common cause of hospitalisation for people who have had diabetes for a number of years.
Up to 20% of people with a diabetic foot ulcer may ultimately require amputation, yet frighteningly, most ulcers appear to be precipitated by a potentially preventable initial event.
| Mäori and Pacific people with diabetes are at a higher risk of lower limb amputation than other people with diabetes living in New Zealand. Notably, there are some specific foot care issues and practices that are different in these cultural groups, and it is most important that these considerations are respectfully acknowledged, whilst still maintaining good practice with regards to foot care. |
What’s covered on this page
Why Legs and Feet are Affected by Diabetes
- Factors contributing to the DIABETIC FOOT
- Neuropathy contributing to foot problems and ulceration
- Large vessel disease
Vascular Disease – Peripheral Arterial Disease (PAD)
- Ankle-Brachial Pressure Index
- Intermittant Claudication (IC)
- Treatment and Medical/Surgical Procedures for PAD
- Gangrene
The ‘At Risk’ or ‘High Risk’ Foot
Specialist Foot Care Services –
Podiatry – Foot Clinics
Foot Deformities
- What is an Ulcer?
- Ulcers in People with Diabetes
- Clinical Descriptions of Ulcers – (Basic Classification)
- Treatment of Ulcers
- Infection and Ulcers
Why legs and feet are affected by diabetes
Diabetic leg and foot problems are caused by a number of independent, but often interrelated factors. Poor glycaemic control, neuropathy and disease of the large blood vessels carrying blood to the legs and feet are the main initial long-term culprits. Add to these a slight foot deformity, injury, followed by infection, and you have more than enough ingredients for a “diabetic foot“.
| Factors contributing to the DIABETIC FOOT Poor diabetes control Neuropathy Peripheral arterial disease (Atherosclerosis) Foot deformity and/or reduced joint mobility Poor footcare Persistant trauma/Injury Infection Poor wound healing |
Neuropathy
Of the factors involved in complications of the foot, neuropathy is considered to be the most significant. Neuropathy in itself is a diverse complication, and it is possibly the combination of motor neuropathy and sensory neuropathy that render a diabetic person’s foot most vulnerable for further complications. Indeed, diabetic neuropathy is said to increase the risk of ulceration 7-fold (2) .
| Neuropathy contributing to foot problems and ULCERATION Diabetic neuropathy affects numerous different types of nerve pathways – sensory, motor and autonomic nerves can all be affected (see neuropathy section for more detail). When motor nerves are affected by diabetes, muscle tissue starts to break down, posture and gait are affected, and foot deformities can result. Foot deformities all too often cause the person to walk differently to normal and the resultant different pressures on the foot makes the foot more liable to ulcerate. When sensory nerves are affected by diabetes, pain or discomfort may go unnoticed. Repetitive trauma or mechanical stress, or a single injury, may not be noticed until the damage is done and an ulcer has formed. When autonomic nerves and pathways are affected by diabetes, the ability of the feet to sweat in response to heat may be impaired. This condition is called anhidrosis. Anhidrosis can result in very dry skin, which cracks easily and is vulnerable to bacterial invasion leading to infection. Alteration of the autonomic regulation of blood flow to the surface of the foot and to the bony tissue also contribute to diabetic foot problems. >> Go to section on ULCERS |
Large vessel disease
Atherosclerosis or ‘hardening of the arteries’ in the legs leads to a reduced blood flow to the tissues that those arteries supply. Peripheral arterial disease (PAD) renders a person with diabetes vulnerable to poor wound healing and persistent infection. This condition is covered in more detail in the following section: “Vascular Disease – Peripheral Arterial Disease (PAD)”
Vascular Disease – Peripheral Arterial Disease (PAD)
Peripheral Arterial Disease (PAD) is a general term used to describe a number of disorders that are characterised by reduced blood flow to the limbs, essentially the lower legs and the feet. PAD renders a person with diabetes vulnerable to poor wound healing and at risk for persistent infection, particularly in the feet.
The degree of blood glucose control is an independent risk factor for PAD; it has been reported that with every 1% increase in glycosylated haemoglobin (this equates to HbA1c), the risk of PAD may increase by 28% (3).
Atherosclerosis or ‘hardening of the arteries‘ is a major factor when it comes to foot and leg problems in diabetes. This process is described in more detail in the sections on heart disease. Heart disease and PAD are closely linked.
| Atherosclerosis, PAD and the ISCHAEMIC FOOT In a similar way that atherosclerosis reduces oxygen supply to the heart in coronary heart disease, atherosclerotic lesions affecting arteries in both the upper and lower leg can result in reduced blood flow to the foot or lower leg. The reduced oxygen supply to tissues is referred to as ‘ischaemia‘. An ischaemic foot has a reduced blood supply that significantly complicates wound healing. Diabetes is associated with a 2-3x increased risk of accelerated atherosclerosis. >> More on atherosclerosis |
Although many patients with PAD have no symptoms, or have atypical symptoms on exercising, approximately one third will experience intermittent claudication (see below), described as aching, cramping, or numbness in the affected limb, occurring with exercise and relieved at rest.
Severe PAD leads to a condition in which the limb is starved of oxygen – critical limb ischaemia. This increases the risk of ulceration and the risk of subsequent loss – or partial loss – of the limb i.e. amputation. Severe PAD is also associated with pain even on resting.
PAD can be detected with Doppler studies and use of the ankle-brachial pressure index (ABI) – see below
NOTE: The painful symptoms of PAD may be masked by peripheral (sensory) neuropathy.
Ankle-Brachial Pressure Index (ABI, or ABPI)
A widely recommended for PAD is the ankle-brachial index (ABI), which measures the ratio of systolic blood pressure in the ankle and the arm. The ABI can be used to detect decreased blood pressure distal to (further on from) sites of artery narrowing. Blood pressure cuffs are placed around ankles and arms. The cuffs are inflated briefly above normal systolic blood pressure. Once the cuffs are deflated, blood pressure measurements are taken using a Doppler instrument. The arm and ankle systolic blood pressure measurements are recorded. Then the ankle systolic pressures are divided by the highest arm pressure to establish an ABI measurement for each leg. The ABI range that is generally considered ‘normal’ is 0.95 – 1.2.
The ABI is a simple and cheap test for PAD.
| The Anckle-Brachial Index in People with Diabetes The use of the ABI is not always straightforward in people with diabetes, as a measure of arterial stiffness – readings may be falsely low on account of increased calcification* of arteries (which makes them less pliable). The health professional should therefore also take consider other characteristics; the person who presents with cold and/or hairless lower limbs, may have PAD even if the ABI test suggests no PAD. A treadmill test is useful in determining exercise tolerance. Toe-Brachial Index (TBI) For patients with rigid ankle blood vessels, toe pressure measurements may be taken since toe arteries are rarely rigid. This examination is called a toe brachial index (TBI) and is a calculation based on the systolic blood pressures of the arm and the systolic blood pressures of the toes. The examination is similar to the ABI except that it is performed with a photoplethysmograph (PPG) infrared light sensor and a very small blood pressure cuff placed around the toe. A TBI of 0.8 or more is ‘considered normal’. Alternatively, a leg arterial ultrasound test can detect PAD if the ABI is not considered reliable. *Increased calcification of arteries in people with diabetes is not without it’s own complications … >> more on calcification of arteries |
The ABI can predict how severe a person’s atherosclerosis is, and the risk of future leg problems (such as development of future leg rest pain, poor healing of foot wounds, need for leg bypass surgery, or amputation). It can also predict the risk of future problems from atherosclerosis in other parts of the body (such as heart attack and stroke). Lower ABI values are associated with a higher risk.
Following the ABI (or TBI) year on year can help to inform whether the PAD is reasonably stable, or is getting worse, and may require surgery.
| ABI Values Normal range 0.95 – 1.2 Low result (Moderate disease) 0.40 – 0.80 Very low result (Severe disease) < 0.40 The ‘normal’ value for ABI is generally quoted as: 0.95 – 1.2 An ABI value of 0.40 – 0.80 is moderately decreased, and such patients often experience some symptoms such as pain in the legs. Attention to foot care is extremely important to prevent accidental injury or infection. Again, any evidence of PAD is associated with future risk of heart attack and/or stroke. Serious efforts to keep one’s risk factors under control are essential to keep PAD from getting worse. An ABI value of less than 0.40 indicates severe PAD. Patients should be extremely careful to avoid any foot injuries. Proper foot care may prevent development of ulcers, non-healing wounds, pain when resting, or gangrene. Usually, care from a vascular specialist is required. The specialist will evaluate the risk and benefits to improve leg blood flow through surgery or other interventions. |
Intermittant Claudication (IC)
The main symptom of PAD is pain in the calf, particularly on walking. This is known as “intermittant claudication” and is pain caused by a lack of oxygen supply to the leg. In many ways it is similar to the pain of angina suffered when there is a poor blood supply to the heart muscle.
The pain experienced with IC can significantly reduce walking speed and distance, and can lead to loss of function and effective disability in the long term.
However, not all people realise the siginificance of the pain; and some people do not experience any significant pain.
Treatment for PAD
Treatment options vary, and depend on the severity of the diagnosis, and the circumstances and exisitng prescribed medication regimen for the patient. Key factors in managing PAD include the following:
- Exercise
- Medication
- Diet
- Smoking cessation
- Diabetes management
- Blood pressure management
- Foot care
- Endovascular therapy (see box below)
- Vascular surgery (see box below)
| Medical Procedures for PAD Endovascular therapy aims to improve blood flow to a leg: Stent A medical device made of an expandable wire mesh tube that is inserted into an artery narrowed by plaque. Once inserted it can expand and hold open the artery, allowing the blood to flow through. Angioplasty Using tools that allow the specialist to work inside the artery, a tiny balloon is placed directly in the narrowed vessel. Liquid is put in the balloon; the balloon expands, and opens the blockage. The balloon is then deflated and removed. Surgical procedures re-route the blood flow around the blockage and use either a piece of synthetic material, or the patient’s own vein. |
Gangrene
Gangrene is basically the death of a significant area of body tissue. It can occur as a result of infection or injury. In people with diabetes it usually occurs with loss of vascular supply (i.e. in PAD when considering limbs) and is followed by bacterial invasion and putrefaction.
Gangrene requires urgent evaluation and treatment…
In essence, dead tissue should be removed to allow healing and prevent further infection. Depending on individual circumstances, possible treatment options may involve one or some of the following:
- An emergency operation to explore or remove dead tissue
- Amputation of the affected body part
- Repeated operations to remove dead tissue (this is termed “debridement”)
- An operation to improve blood supply to the area (see above)
| Concerned? Call your doctor if: An area of the skin on your leg or foot turns blue or black You have a fever A wound appears not to have healed There is foul-smelling discharge from an area on your leg or foot |
The ‘At Risk’ or ‘High Risk’ Foot
If you have had diabetes for some time, have neuropathy, atherosclerosis, signs of heart disease or other vasular disease, and/or have an existing foot deformity, then you are at an increased risk for ulceration.
There have been a number of ‘classification systems’ described in the medical literature, suggesting how diabetic foot risk should/could be categorised, and then, further down the line, how ulcers may be categorised… Systems and processes are important in research in terms of defining a condition, and how best to avoid it, or treat it. But with regards to complications of feet and legs in people with diabetes, the author believes that, for the patient, it is enough to comprehend level of risk, and to understand the appropriate management of that risk. See refs (6-10) if you need more detail on classification.
The ‘At Risk’ foot can further be subdivided into two types – neuropathic and neuro-ischaemic feet. Of people with diabetes presenting at foot clinics, about half have are reported to have neuropathic feet and half have neuro-ischaemic feet (11,12).
| NEUROPATHIC FOOT Neuropathic feet tend to be warm, numb, dry, and usually painless. Blood supply is reasonable and pulses able to be detected. The two main complications affecting ‘neuropathic feet’ are: Charcot (or neuropathic) joints, and Neuropathic ulcers (found mainly on the soles of the feet). In people with neuropathic feet, minor trauma (such as that caused by poor-fitting shoes, walking barefoot, or from a single acute injury) can precipitate a chronic ulcer. Neuropathic feet tend to be insensitive, so that continued walking on the foot causes more damage. NEURO-ISCHAEMIC FOOT Neuro-ischaemic feet are cool, blood supply is reduced and pulses are usually absent. The feet may be dry, and numb, and insensitive to pain as well. Complications of ischaemia – intermittent claudication, rest pain and gangrene may occur. However, in some cases there may be no pain in spite of notable ischaemia. Neuro-ischaemic ulcers, resulting from localised pressure damage, are found mainly at the edges of the feet. |
| PURELY ISCHAEMIC FOOT Purely ischaemic feet (no obvious signs of neuropathy present) are much less common, but are managed in the same way as neuro-ischaemic feet. |
Identification of the ‘At Risk’ Foot
People with diabetes should have their feet checked at least once a year by a health professional specially specially trained to detect diabetic foot problems. Usually this will occur during the Annual Review, which is a yearly check free of charge to people living with diabetes in New Zealand.
A lower limb check should include assessment of the following:
- Peripheral neuropathy
- Arterial/vascular disease
- Potential foot deformities
- Any existing lesions – ulceration or infection
- Review of skin and nail care
- Review of eyesight and mobility – i.e. ability to perform self-care
- Observation of gait (how you walk)
- Observation of footwear – worn footwear can reveal abnormal presure points and areas at higher risk of ulceration.
| Assessing foot risk | ||
| Neuropathic Foot | Assess presence of neuropathy |
Peripheral neuropathy commonly affects sensory
& motor nerves of the lower limbs.
Decreased sensation to touch and pain;
10g Semmes-Weinstein monofilament on plantar
surfaces (four sites on the forefoot (great toe
and the base of first, third and fifth
metatarsals));
Vibration sensation can be tested using a 128
Hz tuning fork applied on the bony prominence of
the great toe, gradually moving upwards if there
is any impairment in sensation noted. A biothesiometer is a handheld device that assesses vibration perception threshold (cut-off point for ulcer risk >25 volts); Impaired deep tendon reflexes; Reduced proprioception may occur later. |
| It is crucial to identify the presence of Charcot neuroarthropathy as this is likely to go unnoticed by the patient until a grossly deformed insensitive foot results, which is highly likely to ulcerate |
Neuropathic Joint Damage
NOTE: Painful, red,
hot, swollen foot – it is sometimes difficult to
differentiate between infection, cellulitus, acute
gout or osteomyelitis and Charcot foot. Series of X-rays may show fractures, new bone formation and/or joint disorganisation. Bone scan can confirm. >> See below for more on foot deformities | |
| Ischaemic Foot | Asess presence of vascular disease |
Are ankle pulses easily detected (“palpable”)?
If not, assess need for referral to vascular
specialist
In people with diabetes, vascular disease of
the lower limb is usually bilateral and
symmetrical;
Leg pain on resting (claudication),
ulceration and gangrene are all clinical signs
of leg ischaemia [Pain may be absent in presence of peripheral neuropathy] |
Management of the ‘At Risk’ or ‘High Risk’ Foot
Management of the diabetic foot is based on risk category.
- LOW RISK – (normal sensation, palpable pulses) – general foot care edcuation and regular (yearly) review
- AT INCREASED RISK – (neuropathy, absent pulses, or other positive risk factor) – enhanced education, frequent review (3-6 monthly), routine podiatry care.
- AT HIGH RISK -(neuropathy or absent pulses plus deformity or skin changes, or previous ulcer) – intensive education, frequent review (1-3 monthly), specialist podiatry care
- ULCERATED or INFECTED FOOT – organised and coordinated care is required from a multidisciplinary team ideally including: General Practicitioner (GP), Diabetes Specialist, Diabetes Specialist Nurse/Educator, Vascular Surgeon, Podiatrist, Orthotist, Vascular Specialist
Specialist Foot Care Services – Podiatry – Foot Clinics
Regular podiatry care should include treatment of early foot conditions such as callus, corns, ingrown toe nails and protection of high risk pressure areas (e.g. with orthotics – specialist footwear or insoles, which help balance out uneven or excessive pressures).
Structured education should also be a standard component of podiatry care for all people with diabetes. Specific, individualised foot care education should also be carefully considered.
Treatment for ulcers may involve debridement (removal of dead tissue), treatment of infection, and relief of weight bearing for example by plaster cast or prescription bed rest. If healing is slow, vascular re-assessment is essential, even in the absense of symptoms of PAD.
| Reduced mobility Special arrangements made be required to enable access to specialist foot care services, especially or those people with disabilities or immobility. |
Published evidence is now starting to show that a multidisciplinary foot care team can improve the speed of ulcer healing, reduce the ulcer recurrence rate, and reduce the number of subsequent amputations in people with diabetes with high risk feet insert refs. see diabetic medicine vol26.no.11. p.1082
| The Foot Care Team A foot care team might involve a doctor with a special interest in diabetes footcare, a podiatrist, a specialist nurse (preferrably with formal training in footcare), an orthotist, an infectious disease specialist and/or medical microbiologist (or ready access to these), and a vasclar surgeon and orthopaedic surgeon (or ready access to these). A social worker, and a psychologist readily (ideally) complement the footcare team. |
Ideally, a comprehensive foot care service, would provide ready access to foot pressure distribution measurements, and sophisticated vascular scanning and angiography would be available to the foot-care team.
Foot Deformities
Foot deformities add to the increased risk of ulceration in people with diabetes. Deformities may be existing, but more commonly, foot deformities arise as a result of neuropathic changes – another consequence of long-term diabetes.
Charcot Foot
Charcot neuroarthropathy affects feet with reduced sensation, but an adequate blood supply. Bone and joint tissues are effectively broken down and remodelled.
Whilst Charcot foot is not exclusive to diabetes, diabetes is currently the commonest cause of the neuropathy that contributes to Charcot’s disease. It is not a new phenomenon – the Charcot foot was recognised as a complication of diabetic neuropathy back in 1936.
Charcot foot is particularly common in people with diabetes who have a history of neuropathic ulceration. And it works the other way too – the insensitive and deformed Charcot foot is at an increased risk of ulceration.
During the acute phase, the affected foot is often inflamed, red, swollen and hot, and it may be painful.
| How does Charcot foot evolve? | |
| Neurotraumatic theory A simple theory Destruction of the bone simply results from repeated trauma or a single minor injury to an insensitive foot: | Neurovascular theory A more complex theory Destruction of the bone results from an exaggerated inflammatory response to repeated trauma: |
|
loss of pain and proprioception – as a
result of peripheral sensory neuropathy plus repetitive mechanical trauma to the foot (which often goes unnoticed) Repetitive trauma leads to multiple tiny fractures (microfractures) that are reluctant to heal. |
loss of pain and proprioception – as a
result of peripheral sensory neuropathy plus repetitive mechanical trauma to the foot (which often goes unnoticed) plus altered bone blood flow* – as a result of autonomic neuropathy – and exaggerated inflammatory response * Increased blood flow and periarticular osteopenia by activating osteoclasts (osteoclastogenesis)… Osteoclasts are bone cells that cause progressive bone destruction (osteopenia) leading to further fractures. |
| Continued weight-bearing (due to lack of perception of damage) can lead into a vicious circle. Changes to the distribution of forces on the joints and bones of the already damaged foot may lead to further damage – microfracture or dislocation. | |
| Motor neuropathy may contribute to the overall process of damage by altering muscle control, balance, and causing the stretching of ligaments. |
Management of the Charcot foot
The treatment of choice for acute Charcot foot is complete immobilisation, and nonweight bearing. This means that the foot is not moved, and the foot is not rested on.
Immobilisation
Complete immobilisation may be necessary for anything from 8 to 32 weeks. This may involve the use of casts, splints, or braces (see “Off-loading” below..
The process of “nonweight bearing” can be aided with the use of crutches, walkers, or wheelchairs. Nonweight bearing is a very important feature of the treatment. Failure to adequately remove all pressure on the foot may result in further fractures occurring, and progression of the joint deformity. A “nonplantigrade” foot may ultimately result – this is the clinical classification for a foot of which the sole doesn’t make full contact with the ground, and relates to a severe permanent foot deformity.
The ultimate goal of immobilisation therapy is to allow for the foot to ‘set’ in a shape that will eventually allow some reasonable level of mobility, with minimal risk of ulceration.
Claw Toes, Hammer Toes, Mallet Toes
Hammer, claw, and mallet toes are toes that do not have the right shape. The muscles that control the toes are affected by motor neuropathy and the resultant muscle wasting causes the toe to effectively bend into an odd position at one or more joints. These toe problems usually occur in the four smaller toes, but not so much in the big toe. PAD and peripheral neuropathy also contribute to the development of these toe deformities.
- A hammer toe is a toe that bends down toward the floor at the middle toe joint. It usually happens in the second toe. This causes the middle toe joint to rise up. Hammer toes often occur with bunions.
- Claw toe often happens in the four smaller toes at the same time. The toes bend up at the joints where the toes and the foot meet. They bend down at both the middle joints and at the joints nearest the tip of the toes. This causes the toes to curl down toward the floor.
- A mallet toe often happens in the second toe, but it may happen in the other toes as well. The toe bends down at the joint closest to the tip of the toe.
| Footwear is important for people with diabetes Tight shoes are the most common cause of hammer, claw, and mallet toes. Wearing tight shoes can cause the toe muscles to effectively get out of balance. Two muscles work together to straighten and bend the toes. If a shoe forces a toe to stay in a bent position for too long, the muscles tighten and the tendons contract. This makes it harder to straighten the toe again. After a time, the toe muscles cannot straighten the toe, even if you are not wearing the shoes. >> see “Footwear” subsection, below |
Misshapen feet in people with diabetes are at high risk of ulceration and need extra care. Make sure that you get the specialist foot care and advice you need. Ask questions if you are unsure of something.
Callus, Corns & Bunions
A callus is an particularly tough area of skin on the fot which has become thick and hard as a response to repeated contact or pressure. The formation of calloused skin is and is an attempt by the body to protect the foot. The dead skin effectively forms a padding over the vulnerable tissue when exposed to repeated pressure.
A corn (heloma) is form of callus commonly resulting from wearing poorly-fitted (tight) shoes. Any underlying foot deformities may additionally encourage such formation of callus. Corns may be painful, but not always in people with diabetes with reduced feeling in their toes or feet.
Callus can predispose to ulceration, especially if the foot is not very sensitive – i.e. in the presence of neuropathy.
To avoid callus developing, always get a
proper shoe fit for each foot; wear good socks for sports
activities and walking
| SEE YOUR PODIATRIST FOR TREATMENT OF A CALLUS OR A CORN. If you are not registered with a podiatrist then see your GP or practice nurse and ask for a referral. |
A bunion is a deformity at the joint of the base of a toe (usually the big toe, sometimes the little toe). Bunions may occur when the joint becomes abnormally stressed over a period of time. Misaligned big toe joints which can become swollen and tender. Often, the first joint of the big toe starts to slant outwards, and the second jointstarts to to angle towards the other toes. Women who wear high-heeled or pointed-toe shoes are at high risk of developing bunions in later life, although the tendancy for deformity does also tend to run in families.
The vulnerable place between the bones near the base of your big toe grows big may become red, sore, and infected. Once infected – if you have diabetes – the ultimate risk of amputation increases.
Bunions can be removed surgically – see your podiatrist or GP.
Ulcers
About 5% of people with diabetes develop a foot ulcer each year.
What is an Ulcer?
An ulcer is a wound or open sore that will not heal, or which persistently keeps returning. An area of skin is broken down and the underlying tissue can be seen. A foot ulcer can be a shallow red crater that involves just the surface skin. Or it can be very deep, extending through the full thickness of the skin, possibly through to tendons or bone tisssue.
Ulcers in People with Diabetes
People with diabetes are at high risk of developing leg and/or foot ulcers as a result of the knock-on effects of having various forms of neuropathy and/or peripheral vascular disease. Other factors adding to the mix include having a compromised immune system and reduced wound-healing ability.
Normally, the healthy foot has the ability to distribute high forces that are applied on the plantar surface and therefore avoid the development of high foot pressures in one particular area of the foot. However, this ability is greatly impaired in long-term diabetes, – foot changes are related to motor neuropathy and to the restriction of joint mobility. The pressures on certain areas of the foot can be considerably high and lead to injury, even on walking only short distances. Thus, an initiating injury may be from acute mechanical or thermal trauma, or from repetitively or continuously applied mechanical stress. Often the precipitant factor is unnoticed and accidental – for example abrasive rubbing from ill-fitting footwear, or from stepping on a sharp (or not-so-sharp) object whilst walking barefoot. In the presence of sensory neuropathy, the person with diabetes is often unaware of the injury if no pain or discomfort is felt.
Once the skin is broken, many things complicate defective wound healing, including bacterial infection, ischaemia (because of poor blood supply), continuing trauma, and poor management (health care services and self care).
If an infection occurs in an ulcer, which is not treated immediately, it can lead to the formation of an abscess (a confinement of pus), a spreading infection of the skin and underlying fat (cellulitis), a bone infection (osteomyelitis) and/or gangrene (an area of dead, darkened body tissue caused by poor blood flow – see section in “PAD”, above).
Among people with diabetes, a foot ulcer precedes approximately 85% of severe foot infections that ultimately require some part of the toe, foot or lower leg to be amputated.
Clinical Descriptions of Ulcers (Basic Classification)
Ulcers are typically defined by the appearance of the ulcer, the ulcer location, and the way the borders and surrounding skin of the ulcer look. The appearance at the base of the ulcer gives health professionals important clues as to the type and root cause of the ulcer.
Ischaemic (“Arterial”) Ulcers
Ischaemic ulcers are usually located on the feet and often occur on the heels, tips of toes, between the toes where the toes rub against one another or anywhere the bones may protrude and rub against bed sheets, socks or shoes. They also occur commonly in the nail bed, especially if the toenail cuts into the skin (e.g. ingrown toenail or harsh nail trimming practice).
The base of an ischemic ulcer usually does not usually bleed, and may be yellow, brown, gray, or blue-black in colour. There may be swelling and redness around the base of the ulcer. There may also be a redness covering the whole foot when the leg is ‘dangled’, but this may turn pale (almost yellow-ish) if the leg is then raised.
Ischaemic ulcers may be painful at nighttime. You may instinctively feel inclined to dangle the foot over the side of the bed in order to relive discomfort.
Neuropathic Ulcers
Neuropathic ulcers are usually located at increased pressure points on the bottom of the foot. The appearance of the base of the ulcer is variable, depending on the level of vascular disease. It may appear pink/red if circulation is good, or blue/brown/black if the circulation is impaired due to vascular disease. The skin surrounding the ulcer may be calloused.
| Classification of Ulcers Ulcers may be more formally classified using any of a variety of grading systems published in the medical literature. The Wagner-Meggitt classification defines wounds by the depth of ulceration (how deep the hole is) and the extent of gangrene (how much dead tissue) The University of Texas system grades wounds by depth and then stages them by the presence or absence of infection and/or ischaemia. The PEDIS classification grades the ulcer based on measures of Perfusion, Extent, Depth, Infection and Sensitivity. |
Treatment of ulcers
Therapy is generally guided by the extent of ulceration referred to as the “grade” of the ulcer (see section on “Classification of Ulcers“, above)
DRESSING
Initially an ulcer is usually covered with a protective dressing, which will be inspected and re-dressed regularly by a member of the foot-care team – usually your practise nurse, visiting community nurse or podiatrist.
| Dressings for Non-infected Foot Ulcers In many cases, diabetic foot ulcers are not infected, and require only protective bandaging. The characteristics of a good dressing are that it should: perform well in the closed environment of the shoe not take up too much space be capable of absorbing large quantities of exudate without plugging the wound and preventing drainage withstand the pressures and shear forces of walking without failing not cause side effects be easily lifted or removed for regular inspection without adversely affecting the wound Taking the above into account, wound dressings should be chosen with consideration of clinical experience, cost, patient preference and the site of the wound. |
DEBRIDEMENT
A podiatrist may need to remove any hard or dead skin or local tissue that is preventing the ulcer from healing. This is referred to as “debridement”. Surgical debridement using sharp instruments such as a scalpel blade is usually considered the best method. All of the dead and yucky tissue needs to be removed, right down to a healthy bleeding ulcer bed with saucer-like wound edges that suggest the wound is good for healing.
If vasular disease is evident and the arteries in the legs have become narrowed through atherosclerosis then blood flow to the feet and lower legs may be significantly reduced. In such cases, an ulcer may precipitate action from the vascular sugeon in order to save the limb. An operation to bypass, or widen, the blocked arteries may be necessary (also, see “Treatment for PAD” above).
Sometimes such vascular procedures are necessary before debridement can reveal a wound bed that is ready to heal.
OFF-LOADING
In addition, the site of the ulcer may need to be protected from further injury using padding or other measures to relieve pressure from that particular area. This is referred to as “offloading“. Special shoes or shoe inserts (‘orthotics‘) or a plaster cast may be necessary.
| PLASTER CASTS Total Contact Casting (TCC) A specially moulded plaster cast is made; it has a heel for walking and is designed to reditribute pressures evenly through the entire foot. TCC is considered the most effective way of off-loading in order to optimise wound healing in diabetic foot ulcers. Total Contact Casting Advantages Disadvantages Your foot is permanently inaccessible and you have no option but to “comply” with this treatment! You are not immobilised – you can get around with the plaster cast on, although because of the weight and bulk of the cast mobility is somewhat hindered. It works! Specialist training in casting technique is required and application takes time. The cast may cause irritation to the skin. Activities are limited because of the weight and bulk of the cast The wound is not visible or available for inspection*. *A new techinique – Instant TCC uses a semi-permanent removable cast that the health professional can remove easily when required. TCC is not suitable for infected ulcers or if there is significant peripheral arterial disease. |
Unfortunately, on account of the disadvantages noted above, total contact casting is not always the treatment of choice for clinicians; commercial devices such as the half-shoe and short leg walker are more commonly used as alternatives. These are less effective in terms of reducing pressure in the key area, and they are not permanent fixtures so can be removed by the patient.
ANTIBIOTICS
If there is any evidence of infection, then antibiotics may be prescribed. A minor operation may be required to drain pus and clear dead tissue if the infection is severe. Intravenous antibiotics (given directly into a vein) are needed in the presence of cellulitis or osteomyelitis, and prompt referral to hospital is usually necessary. (Also, see “Infection and Ulcers” below)
Many foot ulcers DO heal with the above measures, although the healing process can take some considerable time.
Infection and Ulcers
Infection is rarely the direct cause of an ulcer, but, once an ulcer becomes infected, the risk of amputation is greatly increased.
| Factors that increase the risk of wound infection Ulcer > 30 days Ulcer reoccurrence Size and depth of ulcer Peripheral arterial disease (PAD) present |
Infection can be divided into superficial and local, soft tissue and spreading (cellulitis), and osteomyelitis (where the infection has spread to the bone). Typically, more than one type of organism is involved, including Gram-positive, Gram-negative, aerobic, and anaerobic species. Staphylococcus aureus is the most common pathogen in osteomyelitis.
The initial diagnosis of infection is usually based on clinical appearance of the ulcer, relying on signs such as erythema (redness), edema (swelling), pain, tenderness, and warmth. Differential diagnosis of the infection can then be verified using various diagnostic methods, including cultures, and radiographs, or more advanced imaging techniques.
| MRSA – methicillin-resistant Staphylococcus aureus |
Treatment for infection
Treatment of an infected diabetic foot ulcer should be started off with a broad spectrum antibiotic regime, along with appropriate debridement and dressing (see above). Later, the antibiotic regime can be modified depending on the swab culture (which determines which organisms have invaded your ulcer) and sensitivity results (how the organisms respond to given antibiotics, i.e. whether they are resistant or not). In the diabetic foot, the bacteria most likely responsible for non-limb-threatening infections are staphylococcus and streptococci, while limb-threatening infections are generally the consequence of a polymicrobial infection.
Since foot ulcers in people with diabetes are often colonised by a mixture of organisms, so routine swabs may be of limited value.
Seemingly no single broad spectrum antibiotic regimen has been shown to be more effective for diabetic foot ulcers.
Even if the ulcer has itself not fully healed, antibiotics can be stopped once the infection is cleared. Two weeks of antibiotic therapy is the usual guideline, although recalcitrant infections sometimes require longer to resolve.
Unfortunately, sometimes the infected ulcer may still worsen, and fail to heal, in spite of the very best intervention. Sometimes infection spreads to nearby bones or joints which can be difficult to clear, even with a long course of antibiotics. Sometimes the tissue in parts of the foot just cannot survive. In such cases, the solution is usually to amputate the affected part, before the situation becomes life-threatening.