WHAT IS THE CHARCOT FOOT ?
It is a problem which can affect the foot in people with neuropathy (nerve damage with
numbness). The bones of the foot become very fragile and can start to break or dislocate
in response to very minor forces – even in response to the forces which occur with simply
standing or walking. The commonest cause of the Charcot foot is diabetes, but it can
occur in people who have a different cause of nerve damage. It is rare – and affects only
about 1% of people with neuropathy in diabetes. When, however, it occurs, it can lead to
gross deformity or ulceration of the foot and may even result in amputation of the lower
part of the leg.
Why is it called “Charcot foot” ?
It is named after the French Physician/Neurologist who first described these changes in
detail in two classic papers, published in 1868 and 1883. His name was Jean-Martin
Charcot (pronounced “Shark-o”).
Figure 1 Jean-Martin Charcot
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What is a Charcot foot, and what does it look like ?
It starts as an episode of inflammation (warmth, redness and swelling). There may be
some aching discomfort, or it may be painless. Sometimes it is brought on by a minor
injury (such as tripping over something on the floor), but it often just starts for no
obvious reason. Unfortunately, many doctors are unaware of the significance of the
Charcot foot and if a person with diabetic neuropathy who has got inflammation like this
goes to their family doctor or to someone in the emergency room, they may be told that
they simply have an infection, or have a sprained their ankle.
Figure 2: The acute Charcot foot starts with an episode of
inflammation which may look like a sprain, or like infection
The message for any person who has diabetes and with neuropathy and who gets
inflammation of the foot is:
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Take the weight off it as much as you can
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Seek the advice of an expert in diabetes, or a specialist podiatrist, and ask if it
could be a Charcot foot.
Why is it important to take the weight off the foot ?
The reason is that the bones of the inflamed foot are very fragile, and may break or
dislocate if the foot is exposed to any force at all – even just standing and walking.
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Indeed, there may already be fractures or dislocations at the time that the inflammation
starts, and these may be obvious on a simple X-ray. The fractures may ache but there is
little real pain because pain sensation is reduced by the neuropathy. Once again, the best
treatment is simply to immobilise the foot in a fibreglass cast and to rest it.
Some experts in some countries believe that an early operation to stabilise the bones of
the foot will help, but the majority currently avoid surgery. If a patient with an inflamed
Charcot is advised to have an operation, he should ensure that the surgeon is an expert in
the management of this condition. Surgery should not be undertaken without expert
knowledge and skill, and should not be undertaken by a general orthopaedic surgeon or
(in the US) a non-specialist podiatrist.
What happens if weight is not taken off the foot ?
It depends. In some people, the disease seems to be mild and does not result in too much
Figure 3: A typical “rocker bottom” foot caused by
fracture and dislocation of bones in the midfoot
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damage. In others, however, it is severe and the downward forces exerted during standing
and walking cause progressive damage to the shape of the foot – especially if the area of
inflammation is in the middle or back part of the foot, rather than in the forefoot. As the
bones break and dislocate, a bulge can develop on the bottom of the instep (called a
“rocker-bottom” foot). Sometimes, the whole foot bends outwards and there is
dislocation of the ankle. Once these deformities occur, they will never get better without
surgery. Such surgery is usually not undertaken until the whole process has died down
and the inflammation has gone, although some experts (see above) will try to correct the
abnormalities while the foot is still inflamed.
Figure 4: If the skin is not protected, ulceration
can occur over the bone deformities
Unfortunately, the skin which overlies the bone deformities can break down and an ulcer
then develops. Once the skin is broken, infection can enter the foot. If the infection
involves the bone (osteomyelitis), it can be impossible to cure.
In some cases the distortion caused by the process is so bad that the only option is to lose
the lower leg (below-knee amputation).
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Figure 5: The result of continued weight bearing in a
very severe case. The ankle joint has dislocated completely
How is the early Charcot foot managed in a specialist unit ?
The expert physician, surgeon or podiatrist will do an X-ray. If there are obvious changes
to the bones or joints, he/she may do no more by way of investigation. If there are no
obvious changes on the X-ray, they may ask for an MRI (magnetic resonance imaging)
scan. This investigation takes 45-60 minutes and involves the foot being placed in a
strong magnetic field. It cannot be done if there is metal in the foot (from previous
surgery, for example). The MRI scan will show areas of inflammation within the bone
and these are the earliest signs of the condition.
Once the diagnosis is made, the expert will arrange for the foot to be immediately
immobilised in a light-weight fibreglass plaster cast which covers the lower leg and foot,
or some equivalent device. Some people have tried to use removable casts (which can be
taken off in bed, or when the person has a shower, for example), but experience is that
they do not support the foot sufficiently well and the cast which cannot be removed is
better.
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Some centres now also give people a bisphosphonate. Bisphosphonates are medicines
which are used to stabilise or strengthen the bones in osteoporosis and in certain other
medical conditions. Some give a bisphosphonate called pamidronate by a single
intravenous infusion. Others prescribe a tablet - either alendronate or risedronate. Many,
however, give neither because there is no good evidence that they improve the long term
outlook.
Whether or not a bisphosphonate is given, the mainstay of management lies in the use of
the fibreglass cast to protect the foot and to limit and tendency to distortion. The cast will
need to be replaced at regular intervals: usually weekly or every other week.
Does it get better ?
Yes. But it can take a long time. No-one knows what causes the Charcot foot, but it is a
condition which persists for several months (sometimes a year or more) before it
eventually settles, and the bones regain their original strength. It is, however, very
difficult to decide when the process has settled and the only clue lies in comparing the
warmth of the skin of the two feet. There are no other tests which can be used. When it
does eventually settle, the person can go back to wearing shoes again and to normal
weight bearing. The shoes may, however, need to be specially made if the foot has
changed shape. If it has changed shape, it will never go back again – unless a decision is
made to improve the shape of the foot with late surgery. The changed shape will cause
added pressure on the skin which overlies bony prominences. This pressure will lead to a
build of hard skin (called “callus”), and if this is not prevented by wearing fitted shoes, or
is not removed regularly by a podiatrist (chiropodist), it can break down and form an
ulcer.
Does it come back ?
Almost never on the same side, we think. It sometimes flares up again within in a year or
so of apparent healing, but this may be because it was never properly healed in the first
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place. On the other hand, the process may affect the other foot, and is thought to do in
about 20% cases (ie one person in five).
Figure 6: Stable, quiescent disease affecting both feet. The abnormal shape
of the feet is causing the build up of hard skin at points of increased pressure,
and these will break down into ulcers unless the person has regular chiropody
and/or is provided with fitted footwear.
Why does the Charcot foot start in someone with neuropathy, and why is it so rare
when neuropathy is quite common ?
Nobody actually knows, but latest theories have drawn attention to the importance of
inflammation. It has been suggested that anything which can lead to local inflammation
in the foot may trigger the onset of the process in a person who is at risk. This
inflammation might be triggered by an injury, or a previous ulcer or infection, or even an
operation. Sometimes it is not clear.
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Who is at risk ?
Again, there is no way of knowing, but the condition seems to occur most often in those
who have quite bad neuropathy (with loss of sensation in the feet), and yet good overall
blood supply. It is thought that people with hardening of the arteries and poor blood
supply do not get it because they cannot increase the blood flow to the foot sufficiently to
cause the inflammation, and it is the inflammation which is the reason why the bones
become fragile and liable to facture.
Professor William Jeffcoate and Dr Fran Game
Foot Ulcer Trials Unit, Department of Diabetes and Endocrinology,
Nottingham University Hospitals Trust, City Hospital Campus,
Nottingham NG5 1PB
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