Methods For Offloading Pressure On The Foot

The mainstay in the management of an active plantar foot ulcer is the effective offloading of the ulcer area. Once an ulcer is

Offloading Methods For Foot Ulcer
Figure 2.12 Lower side of insole illustrated in Figure 2.11

present, it will not heal unless the mechanical load on it is removed. Among the methods used for this purpose are complete bed rest, crutch-assisted gait, wheelchair, and prosthetics. However, these methods are impractical for the majority of patients to use for a period of several weeks while the ulcer heals. Common approaches for reducing the load on the ulcerated area include the use of a total-contact cast or other commercially-available casts, and therapeutic footwear.

TOTAL-CONTACT CAST

A total-contact cast (Figure 2.13) is a plaster of Paris cast, which extends from knee to toes. This is the method of choice for the treatment of grades 1 and 2 (according to the Meggitt-Wagner classification) diabetic foot ulcers which are located on the forefoot

Total Contact Cast For Diabetic Foot
Figure 2.13 Total-contact cast

and midfoot; the cast reduces peak plantar pressures in these areas by almost 40-80%, but is less effective with ulcers located on the hindfoot. In one study, the use of a total-contact cast resulted in almost 90% of plantar ulcers healing within an average of 6-7 weeks. This method permits walking while uniformly decreasing the pressure on the sole of the foot.

The ulcerated area should be debrided and covered with a thin dry dressing. A total-contact cast is applied with the patient in the prone position and the foot and ankle in a neutral position (i.e. with the foot flexed at a 90°-angle to the ankle). A layer of fiberglass tape is usually applied over the plaster, to strengthen the cast and allow early ambulation. A small rubber rocker is added for walking. A plywood board is inserted between the rubber rocker and the cast in order to minimize the possibility of the sole of the cast becoming cracked. The cast should be changed every 3 -7 days. The use of a total-contact cast is contraindi-cated when infection or gangrene (Meg-gitt-Wagner stages 3-5) is present. Skin atrophy and an ankle brachial index below 0.4 are considered to be relative contraindications to the use of a total-contact cast. Although a total-contact cast permits walking, patients are instructed to minimize their activity in order to reduce the pressure on their soles. Instability and the risk of falls are disadvantages of this cast. Both in- and outdoor compliance is another advantage, especially for the non-compliant patient, since this cast is not easily removed.

OTHER COMMERCIALLY-AVAILABLE CASTS

Removable Cast Walkers

Prefabricated walkers function on a similar principle to the total-contact cast and are removable, commercially available, lightweight casts (see Figure 9.11). They are not designed to provide total contact, and the addition of inflatable or adjustable pads reduces movement of the limb within the cast. A custom-molded removable insole is adjusted to reduce plantar pressure. Use of removable cast walkers allows inspection and dressing of the wound on a daily basis. They may be used in patients with infected and ischemic ulcers. In addition, patients can bathe and sleep more comfortably. The rocker shape of the outsole reduces further pressure on the forefoot while standing and walking. In addition, these casts are ideal for clinics, which do not have personnel with experience in plastering.

Scotch-Cast Boot

This is a lightweight, well-padded fiberglass cast, extending from just below the toes to the ankle, and it is worn with a cast sandal (Figure 2.14). It may be fabricated as a removable or non-removable cast. With appropriate modifications of the pads, the scotch-cast boot reduces pressure on any region of the sole when needed. Removable scotch-cast boots can be used in cases of both ischemic and infected ulcers, since drainage and wound dressings are easily applied. As with the total-contact cast, experience in plastering is required.

PRESSURE RELIEF SHOES (THERAPEUTIC FOOTWEAR)

These are temporary shoes which allow some level of ambulation, while at the same time offloading pressure on the ulcerated area. These shoes are easy to use and are of low cost and since they enable the patient to walk quite normally, they lead

Scotchcast Boot
Figure 2.14 Scotch-cast boot

to a better quality of life. A rigid rocker sole is incorporated in order to reduce the weight-bearing load in the forefoot by up to 40% during walking. The appropriate choice of insole may reduce plantar pressure by an additional 20%. Half shoes (see Figure 3.36) are indicated for ulcers located on the forefoot (almost 90% of diabetic foot ulcers are located in this area). They offload pressure on the entire forefoot, while increasing pressure on the midfoot and heel, permitting the patient to engage in limited walking activities. Instability is a problem, and the patient needs to use crutches. With the use of half shoes the mean time to ulcer healing was reported to be 7-10 weeks in two studies. Patients are instructed to walk on their heel and avoid forefoot contact with the ground at the end of the stance phase. A sole lift

Neuro Lift For Sandals
Figure 2.15 Shoe terms

on the opposite shoe may be necessary to equalize the limb length. These shoes are easily removed for dressing changes.

Heel-free shoes (see Figure 5.18) reduce peak plantar pressure on the heel by transferring pressures to the midfoot and forefoot. They have the same advantages and disadvantages as half shoes. Both half and heel-free shoes are commercially available.

Ulcers located on midfoot (mainly over bony prominences due to neuro-osteoarth-ropathy) are best treated with the use of customized insoles with windows under the ulcerated area.

Shoe terms are shown in Figure 2.15.

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Responses

  • cora
    How to offload pressure from the foot?
    7 years ago
  • adelchi
    Why plaster in a total contact cast?
    7 years ago

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