Charcot Neuroarthropathy (CN) is a distressing condition and it is often difficult to treat and possibly it may well appear to be refractory to treatment. The prospect of keeping a foot and leg inside a below knee, non weight-bearing plaster cast requires many different services and resources.
The patient would not usually be advised or permitted to be weight-bearing during the developmental and active stages of CN. The application of a total contact cast is frequently very time consuming. A total contact cast which is applied without due regard to the risks of long term close contact casting may well be the means by which the patient suffers iatrogenic harm.
The skin of patients with diabetes is easily damaged through friction and shear forces. The prospect of sustained and prolonged skin damage and associated ulceration is an ever-present possibility with diabetic patients.
The changes which accompany chronic diabetes usually dictate that the patient will be subject to substantial changes in their ability to heal. The inevitable reduction in the sensation over the foot is one other valid reason that we see these patients at very frequent intervals (often weekly) and change the cast at every visit.
Notwithstanding that the patient depicted below has had a pressing need to continue to be weight-bearing; the case illustrated and detailed a method of splint application which may well be applicable to a general use case. The method is cost efficient and it appears to be very well tolerated by the patients on which I have used the abbreviated form of cast described below.
Charcot Foot - Aetiology
Damage which we know is the result of neuropathy was first described when it was related to the condition tabes dorsalis. (Charcot, 1868) It was subsequently attributed to diabetes mellitus (Jordan, 1936) which is seen as one of the main causes of CN because of the diabetic patient's tendency to develop peripheral neuropathy. One classification of CN was devised by a research worker (Eichenholtz, 1966) who had proposed three distinct stages.
Stage I - Developmental or Acute stage.
Stage II - Coalescent or Quiescent stage.
Stage III - Consolidation or Reconstruction and Reconstitution stage.
Chantelau and Grütznerb (2014) examined the value of the Eichenholz classification. They concluded that Eichenholz's classification of a Charcot joint was unable to detect the earliest, nondeforming, X-ray-negative inflammatory stage of the acute Charcot joint; which is only visible to Magnetic Resonance Imaging techniques.
They noted that if the earliest stage is treated in time, that the healing takes place without significant arthropathy. By contrast, treatment of the disease stages proposed by the Eichenholz classification inevitably results in foot deformity and major arthropathy. These researchers proposed a classification based upon the absence or presence of cortical fractures and whether the disease process was active or inactive, based upon the absence or presence of skeletal inflammation.
The Charcot joint disease process predominantly affects the midfoot in the diabetic patient. The diabetic patient population and the midfoot site tend to be highly amenable to conservative treatment. The results for the non-operative treatment of the hindfoot or the ankle joint are not as encouraging. Non-operative treatment tends to be reserved for the cases where the joint is seen to be at the developmental or acute stage of disease progression.
Plain radiographs may be a helpful adjunct when confirming CN. Loss of the longitudinal arches in the foot indicates the descent of the midfoot which comprises the cuboid, navicular and cuneiform bones. The image below depicts a collapsed midfoot.
Conservative treatment may be used for clinically stable deformities which do not compromise soft tissues. Where the deformities do not involve infection in the soft tissues or bony infection, then conservative treatment may be chosen. Patients who have inadequate circulation, which does not have a high enough perfusion rate to support surgery, or patients who are at risk from general anaesthesia, will usually be assigned to a conservative treatment pathway.
On arrival, the new patient with a suspected case of CN is rested on a couch. They have their shoes and socks removed and they rest for 30 minutes to allow the temperature of both feet to stabilize. After 30 minutes have elapsed; infra-red skin thermometry is conducted.
The temperature measurements are taken from the skin over the listed joints on both feet and comparisons are made between each bilateral reading. An average of the ten readings for each side is calculated and compared. This assists the treating clinician to make a clear diagnosis.
It is thought that joints with active CN exhibit a raised temperature of approximately 2 °C higher than normal joints. When comparisons are being made between the right and left foot, the averaged figure for the ten readings would raise one's index of suspicion for CN if it is around 2 °C or more higher than the contralateral foot. (Najafi & Wrobel et al, 2012)
One place I have worked measured patient foot temperatures every four weeks. The multiple subtle shifts in temperature each week are unhelpful in describing clear patterns of temperature difference. Three clear reductions/normalised temperature readings were observed before it was considered that the Charcot joint had entered the coalescent phase and weight-bearing could be initiated.
It was demonstrated (Lavery & Higgins et al, 2004) that knowing the skin temperature (measured by the subjects in their own home) which was measured from six different sites, had prevented all but one out of 41 subjects from developing ulcers.
Ulcers were shown to be a predictor of amputated limbs. The control group of 44 patients (no measurements of skin temperature were taken) went on to develop seven ulcers, two charcot fractures and two infections. There were also two foot amputations within the control group.
An evidence based assessment, diagnosis and comprehensive treatment pathway was developed (Milne & Rogers et al, 2013) and encapsulates much of the current thinking and research on treating patients with acute CN. The paper utilised the generally agreed 2 °C temperature difference, between the involved foot and the contralateral foot, as one of the definitive differences in cases of CN versus the cases where CN was not established.
Clinical practice guidelines (Frykberg & Armstrong et al, 2000) have been defined but the clinical practices employed throughout the NHS (the author has worked in around 400 NHS hospitals during the last 6 years) appear uncontrolled, inconsistent and based in local belief rather than evidence.
An example record form for logging temperature measurements
The record form shown above is reproduced by kind permission of Mr James Vincent; Senior Orthopaedic Practitioner at Dorset County hospital.
The overall length of the leg below the knee and the foot to be cast was measured and the width of the patient's limb is noted. Woodcast splint material was marked for cutting while it was being heated on the plate of the warming machine.
The splint was heated and cut to the length and width dictated by the measurements. Woodcast splinting material is far easier to cut when it is soft and warm. The splint was heated to obtain its maximum pliability before being applied to the involved limb of the patient.
The splint was applied over a bouclette stockinette, which had a layer of felt applied along the length of the anterior tibial spine. The splint was shaped and held into place with a crepe bandage for around four minutes. This permitted the splint to mimic all of the contours being cast and supported with the result that the curves in the splint remained in a fixed relationship to each of the copied contours.
Special attention was devoted to the sole of the foot and the underside of the splint. The underside of the splint formed the sole-plate of the cast. Woodcast was pressed firmly into the contours of the foot while being massaged to copy the shape accurately as the Woodcast splinting material was hardening.
The image below shows that the Woodcast splinting material is amenable to being joined. The company supply a ribbon of their splinting material which is 1mm in thickness. This was placed over the line where two short lengths of splinting material were butted together. Two longitudinal strips of ribbon were added for additional strength.
The below knee splint which is shown at various stages of construction, would normally be fashioned from a single length of Woodcast splint material. Having none of the splint material in the appropriate size (4mm x 10 x 80cm) required two smaller pieces of Woodcast splint (4mm x 10 x 40cm) to create the splint demonstrated.
The next two images show the leg covered with Lohmann-Raucher TG Soft bouclette stockinette. This was then covered with a single layer of undercast stockinette.The standard undercast stockinette prevents the Woodcast splinting material from adhering to the bouclette when it is warm. It can also be left lining the Woodcast splint to which it adheres readily when the splint is warm.
It is worth pointing out that the splint does not extend around the leg to a point perceived as halfway... that is to say where the calf and leg diameter is at its maximum. The reason was that the skin of the patient was very friable and we had spent six weeks healing three areas of skin loss which had occurred because of circulatory insufficiency.
The splint was applied to avoid those areas. It was important to provide an adequate splint without causing any further damage to the patient's already imperilled skin integrity. The splint was constructed from 4mm thick Woodcast material and it was perfectly adequate for supporting the weight of the patient, which was measured at 116 kilograms.
The use of 2mm Hapla Fleecy Web edging prevented the hard edge of the Woodcast splint from creating excess pressure on the soft tissues of the leg and foot of the patient. The use of casting pre-tape was to prevent the casting tape from sticking to the soft stockinette and felt materials.
This pre-tape use aids the removal of the soft casting tape which is used to hold the splint in place. It also facilitates and supports the re-use of the splint if it has to be re-moulded to accommodate changes in the surface anatomy of the sole of the foot and foot shape.
Update: The use of casting pre-tape is possibly not necessary. It was used initially while searching for and conducting trials of different methods of securing and removing splints. When using casting tapes that remain soft, they can be removed from the splint easily. It is not yet established as to which is the ideal method to protect the adhesive felt edging and prevent it from adhering to the softcast.
The addition of a post-operative pattern cast shoe completed the cast production. The patient can walk upon the finished cast immediately because the Woodcast material is weight-bearing as soon as it has hardened. The patient was comfortable and required a total of eight weeks for skin loss healing and the Charcot disease process to resolve.
Every individual cast (and the casting process required) was comfortable for the patient. The Woodcast splint was repurposed in the Woodcast Express oven on three separate occasions so as to accommodate any patient foot shape changes. The use of a single roll of 10cm soft casting tape, to secure the splint, was one of the factors which aided a speedy application of the cast as shown.
The time required to remove and apply the cast (once I was familiar with the casting process) was around 10 minutes. The savings in costs (with repurposed Woodcast splints) and operator time provided a huge reduction in the resources required to treat this often intractable condition.
Frequently, orthopaedic practitioners and podiatrists will find themselves involved in the removal and application of Charcot foot casts spanning at least an hour of clinic time. The splinting material has not been used in this application in conjunction with a Bohler frame.
With replicated findings, this abbreviated method of casting for a Charcot neuroarthropathy while using a Woodcast splint as the close contact medium, instead of plaster of Paris, is one way to reduce the call on the time and the resources of the busy plaster room. The increase in diabetes is sure to presage an increase in the number of Charcot joint cases.
Remember: The depicted case included weight-bearing because there was no choice for the patient. Normal Charcot joint therapy involves non weight-bearing of the involved limb.
These final images show the completed cast, which is very easily removed by the simple method of cutting along the anterior tibial spine and dorsum of the foot with a pair of cast cutting scissors. This is the area that was protected with orthopaedic felt before the soft casting tape was applied over it and pre-tape in order to hold the Woodcast splint in position.
Using soft casting tape also precludes the need to use a cast saw and thus reduces the risk of injury to the patient's fragile skin which is easily damaged and difficult to heal. I highly recommend this method of applying a cast for Charcot joint treatment to my colleagues.
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Chantelau and Grützner
Is the Eichenholz classification still valid for the diabetic Charcot foot?
Swiss Med Wkly. 2014;144:w13948
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Home Monitoring of Foot Skin Temperatures to Prevent Ulceration
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Milne & Rogers et al.
Developing an evidence-based clinical pathway for the assessment, diagnosis and management of acute Charcot Neuro-Arthropathy: a systematic review
Journal of Foot and Ankle Research 2013, 6:30
Najafi & Wrobel et al
Plantar Temperature Response to Walking in Diabetes with and without Acute Charcot: The Charcot Activity Response Test
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