Eczematous eruption within cast

A 42-year-old neuropathic man with type 1 diabetes of 40 years' duration was given a total-contact cast for acute Charcot's osteoarthropathy. After 3 weeks he developed an eczematous eruption of the whole area covered by cast and some areas on the other leg and arms.

He underwent patch testing by dermatologists, including testing to epoxy resins. These tests were all entirely negative, making a contact eczema rather unlikely, although it is possible that he was allergic to another component of his plaster.

Our solution was to enclose the cast, inside and out, with three layers of stockinette to reduce any possibility of direct contact of the patient's skin with any other component of the cast, and his skin condition improved.

Key points

• Eruptions beneath the cast may be due to allergy to cast components

• A cast with extra protective layers of stockinette may be useful when patients develop eruptions under the cast

• Patch testing may be helpful.

Rehabilitation programme. Once the ulcer is healed, the patient should be assessed for moulded insoles and bespoke shoes.

He should remain in the cast until the new shoes are ready.

It is helpful if the orthotist attends the casting clinic so that footwear preparations can be underway during the last weeks of healing and unnecessary delays are avoided.

When the patient has been healed for 1 month, the rehabilitation programme can commence, as follows:

• The cast should be bivalved and made removable by cutting out the front, padding the raw edges of both pieces with Elastoplast, and holding the two pieces in place with Velcro strapping or bandage. The padding should be incorporated into the cast

• The patient may walk for five steps without the cast on the first day of rehabilitation, wearing his new shoes and walking within the house. He should then replace the cast

• The foot should be checked for red marks on the following day. If all is well, the patient can walk for 10 steps without the cast

• Very gradually he can build up the amount of walking he does, within the house at first and then outside, but always wearing the special shoes and checking the foot every day for problems

• If blistering or ulceration occur he should return to the foot clinic at once

• Patients may require physiotherapy to build up wasted muscles.

Education for patients in casts. It is dangerous to enclose an insensitive leg and foot in a closed cast without careful education of the patient as follows. ' Keep your cast clean and dry. Walk as little as possible. If you go out in wet weather cover the cast with a plastic bag or cling film, but remove these as soon as you are under cover again

Scotch Cast Boot Pictures
Fig. 4.7 The Scotchcast boot.

• You can obtain a plastic cast protector for bathing and showering

• Check your cast every morning and evening for: Cracks

Soft areas Dirty areas

Stained areas (where blood or pus has come through the cast from the inside) Wet areas Bad-smelling areas

If any of these occur, please telephone the diabetic foot service immediately and come in for a cast check

• Check your temperature with a clinical thermometer every morning and evening. If it rises above 37.5°C, ring the clinic and come in for a check

• Check your blood glucose every morning and evening. If it rises above 15 mmol/L (270 mg/dL) please ring the clinic and come in for a check

• If you feel unwell, tired, hot, achy, shivery or have flulike symptoms, please ring the clinic and come in for a check

• Never poke or pour anything down your cast

• Never try to remove the cast yourself

• Do not go a long distance from home

• Do not fly as there is increased danger of deep vein thrombosis.

Not every patient is suitable for total-contact casting, and the Scotchcast boot is a useful alternative. It can also be used for patients with neuroischaemic foot or cast phobia.

It is a simple removable boot made of stockinette, cast padding, felt and fibreglass tape. Originally the fibreglass tape used was of the Scotchcast brand name: other fibre-glass casting tape can, however, also be used. The boot is effective in reducing pressure on the plantar surface and the margins of the foot. It is made as follows:

• A layer of stockinette is applied to the lower limb from mid-calf to 10 cm distal to the toes

• One piece of 7-mm felt is applied to the sole of the foot extending to the tips of the toes, 5 cm up the back of the heel and 2.5 cm up each side of the foot. Lateral borders should not be higher than the top of the foot. Triangles are cut out of the felt so that it sits snugly around the heel

• Cast padding is wrapped loosely around the foot over the felt

• Three strips of fibreglass tape are cut and overlapped longitudinally so that they cover the sole of the foot. More fibreglass tape is then wrapped around the foot over the strips, keeping well within the area covered by cast padding

• The fibreglass is trimmed away below the malleoli, round the back of the heel and along the sides of the foot below the level of the felt. The fibreglass covering the dorsum of the foot is lifted away, leaving behind as much cast padding as possible. Any sharp corners of fibreglass are rounded off

• The stockinette is folded back over the foot from each end

• The entire boot is wrapped round with Elastoplast tape. At this stage the boot cannot be removed by the patient. If a removable boot is wanted, the procedure is as follows:

• The dorsal area of the boot is cut open from toes to ankle, through all the layers of cast padding and stockinette, and the boot is removed

• The raw edges where the cut was made are sealed with Elastoplast

• A felt tongue is made as extra protection to the dorsum of the foot to avoid rubbing by the straps

• Ready-made straps or Velcro fastenings over the midfoot and high on the foot should be adjustable to accommodate oedema

• A large sock worn over the cast offers extra protection to the toes. The boot can be worn inside a cast sandal.

Removable cast walkers

There are several models of removable cast walker. We have first-hand experience with the prefabricated pneumatic walking brace called Aircast (Fig. 4.8).

The Aircast is a bivalved device and the two halves are joined together with strapping. The cast is lined with four

Pneumatic Vascular Pump
Fig. 4.8 Orthowedge shoe to off-load the forefoot.

air chambers which are inflated with a hand pump to ensure a snug fit. Care must be taken that the cast does not impinge upon the margins of the foot. The Aircast has a rocker sole.

Flat-bed insoles are supplied with the Aircast although they can be replaced by bespoke moulded insoles. Advantages of the Aircast include:

• Practitioners can view the wound and inspect the foot. This is important for practitioners who fear iatrogenic lesions or undetected infections

• Avoids the labour-intensive programme required for plaster casting

• Cast provides an immediate off-loading device

• Cast fits either foot and can be retained for future problems after one episode of ulceration is healed. Disadvantages of the Aircast include:

• It will not accommodate severe deformity

• The cast is easily removable which renders it unsuitable for some patients who may use it only intermittently

• Aircasts should not be issued to very frail and unsteady patients who might fall and injure themselves.

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