Even today there is still a great deal of uncertainty about the causes leading to the establishment of Charcot foot; what we do know for certain is that it is always accompanied by the presence of diabetic neuropathy.
Charcot foot is a foot in which a pathology of the bone and joints of the foot is established: as a consequence of this the bones fragment and become deformed to the extent of losing normal connections between joints.
The structure of the foot is thus greatly compromised: the end result will therefore be a serious deformity of the foot.
If this affliction is not diagnosed and therefore not treated at its onset (referred to as acute Charcot), it evolves into pictures of deformity capable of causing ulcers which are difficult to cure or recurring ulcers which may ultimately even lead to amputation of the limb.
Documented epidemiological data is very scarce and inconsistent: this is because little is known about this pathology which is often underestimated.

Acute Charcot
The acute onset of Charcot foot is characterised by signs of acute inflammation: reddening, pain and increased temperature of the foot; minor fractures are also possible ( Figure 20), which may even be missed on the X-ray examination.
The problem of correctly diagnosing Charcot in its acute phase results from the fact that presence of pain, oedema and reddening of the foot may be interpreted as symptoms of sprain, phlebitis, infection of the soft tissues or other problems ( Figure 21); in this case the patient continues to walk, aggravating the disease.
Evaluating the temperature of the foot, which is raised by at least two degrees in comparison with the foot on the other side ( Figure 22), and an X-ray, to be repeated 15 days after the first one and then at subsequent points in order to monitor development, are essential for correct diagnosis in the acute phase.
If an intervention is carried out at the onset of Charcot, this can halt or at least slow down the process of bone degeneration by attempting to prevent the foot from becoming deformed.
Treatment in the acute phase of Charcot consists of immobilisation using a rigid ankle boot (different from the off-bearing apparatus used to treat neuropathic ulcers); it is absolutely essential in this phase for the foot not to be incorrectly supported on the ground because the load worsens bone disruption.
This ankle boot must be worn for many months (at least three/four); generally combined with medical treatment using diphosphonates.
Once the clinical picture has stabilised, it is essential to prescribe an orthesis with a made-to-measure shoe and arch support cast which holds the foot and ankle perfectly ensuring that it is stabilised as much as possible when the patient is walking.

Chronic Charcot
If the acute phase is not correctly diagnosed and treated and the patient continues to walk with ordinary shoes, progressively the relations between the various bones in the foot change, normal relations between the joints are lost, fragmentation and local detachment occur.
All these anomalies increase in time and lead to increasingly serious clinical pictures of deformity ( Figure 23) until it is impossible to distinguish the bones from each other (on the X-ray the foot looks like a bag of bone fragments).
As it is logical to expect, the more deformed a foot becomes the more likely it is for ulcers to form, and the more serious the deformity the more difficult it is to cure these ulcers.
The gravity of Charcot is closely associated with the original position of the part of the foot involved in the process: if the front of the foot is involved there is a low risk of amputation, the risk is higher when the middle of the foot is involved (cuneiform, cuboid and scaphoid joints) and is a very high if the ankle is affected.
A serious problem comes into play if the Charcot presents an ulcer; in this case carrying out a differential diagnosis between Charcot without osteomyelitis and Charcot with osteomyelitis is essential in order to define treatment measures.
Often a standard X-ray alone is not sufficient but more sophisticated examinations must be taken into consideration, such as a CAT scan and NMR.
Treatment for chronic Charcot deformities is associated with whether or not an ulcer is present and with the danger that there may be a bone infection under the ulcer.
If infection is present, it is essential to remove the infected bone or bones; hence the need to proceed to carry out major amputation, that is located above the top of the ankle, if the bones at the back of the foot, the calcaneus (heel bone) and astragalus (ankle bone) are involved in the osteomyelitis.
If no osteomyelitis is present it is possible to consider a surgical intervention to correct the deformities; it is essential for the surgical intervention to be carried out once stabilisation can be shown from the clinical picture and from X-rays, even if some American authors have carried out interventions in the acute phase.
The type and site of the intervention depend on the bone deformity.
Sometimes it is possible to carry out simple interventions involving decompressive osteotomy (removal of the part of bone which is causing pathological pressure on the tissues - refer to the section entitled Clinical Cases - clinical case 8 in this respect).
In the case of Chalcot of the middle of the foot it is possible to carry out realignment osteotomies and to use methods of synthesis such as wires or screws ( Figure 24) which can guarantee better stability of the foot.
In the case of Chalcot of the ankle, stabilisation can be achieved using a tibial intramedullary nail.
However you should be aware that although it is fairly simple to carry out an osteotomy intervention, interventions involving realignment and stabilisation are extremely complex and do not always produce a favourable outcome; in any event they always require a long period of treatment after the intervention and made-to-measure shoes to hold the foot and the ankle.
In conclusion we can say that Charcot osteoarthropathy is a pathology which is very serious in itself and this seriousness is further accentuated by an inadequate evaluation; this underevaluation is the result of a failure to diagnose the acute phase and delay in carrying out a surgical intervention in the chronic phase.
However, even if diagnosis and treatment is carried out at exactly the right time this is a pathology which sets a difficult challenge for both the doctor and the patient.