5 Questions-and Answers-About Off-Loading

Advances in Skin & Wound Care, Sep/Oct 2003 by Lavery, Lawrence A

Q: Why is off-loading thought to be effective in managing wounds?

A: Off-loading eliminates one of the most important causative factors leading to foot ulcerations in individuals with diabetes and neuropathy. Many of these wounds are the result of repetitive minor trauma from walking pressures on the sole of the foot. Without addressing this component of the causal pathway, the wound would continue to be reinjured and, in many instances, would remain open.

Complete immobilization allows the tissue to heal without being disturbed or traumatized by repetitive injury that can tear the wound apart. The more restrictive the off-loading modality, the less active the patient will be during the healing process. Immobilization of a wound often reduces pressure and shear forces and reduces the number of cycles of injury to which the wound is exposed. In this respect, treating neuropathic weight-bearing ulcers is similar to the immobilization of a fracture.

Most patients would prefer an off-loading device that is light and facilitates walking; however, realistically, the most effective treatment strategy requires something that will severely disrupt normal activity for 6 to 8 weeks. For example, a patient with a tibia or ankle fracture would not be allowed to walk without proper immobilization. The same holds true for a diabetic patient with neuropathy and a foot ulcer.

Q: What is the best option for off-loading?

A: Various methods are used to off-load wounds. The type of off-loading device selected depends on the wound's underlying pathology, comorbidities, and the patient's profile. The term off-loading most commonly describes treatments for weightbearing ulcers of the foot, but the concept of off-loading is equally important for pressure ulcers. Continuous protection, pressure reduction, and decreased activity provide the ideal environment to heal many foot wounds.

Total contact casts are thought to be the gold standard in treating neuropathic plantar foot ulcerations. This technique was brought to the United States by Dr Paul Brand1 and was taught to many practitioners at workshops conducted at the Gillis W. Long Hansen's Disease Center in Carville, LA. The technique is a modification of a fracture cast. Little padding is used, which allows the cast to contour the lower extremity, providing contact with the entire surface of the foot and lower leg.

Total contact casts are perhaps one of the most frequently described techniques in the medical literature to heal foot ulcers. One advantage of the total contact cast lies in the fact that the extremity is protected every minute of the day. Patients can walk with the cast, but activity is reduced. Recent work by Armstrong et al2 indicates that activity in a total contact cast is significantly less than in other devices.

However, several limitations to total contact casts exist. They are time consuming for health care providers to apply and pose a risk of iatrogenic pressure wounds from a poorly applied cast. They also require some expertise to apply, and patients complain that the casts are hot, heavy, and make walking difficult.

Q: Are there ready-made removable off-loading devices that can be used?

A: In the past few years, a number of off-the-shelf removable cast boots have been developed and marketed to off-load the diabetic foot. Products such as the DH Walker, Bledsoe Conformer Boot, and Aircast Walker have been studied in the gait laboratory and in clinical trials and compared with total contact casts. Several devices have been shown to off-load the foot as effectively as total contact casts.2-5 Custom-fabricated ankle-foot orthoses may also be used6; however, they are expensive and require several weeks to be made. In addition, if the size of the limb changes from edema or muscle atrophy, the custom product may no longer fit properly.

Custom-made and off-the-shelf healing sandals offer another off-loading option. They generally fasten with self-adhesive straps and have a foot bed made of single- or double-density viscoelastic materials to cushion the foot. They can also be made with a rocker sole or a metatarsal bar to facilitate pressure reduction on the ball of the foot. However, these devices are usually less effective than total contact casts or removable cast boots at reducing peak foot pressures.3,4

Use of padding techniques that arc glued or taped to the sole of the foot have also been reported in the medical literature. These techniques can be used with healing sandals or in removable cast boots. Although generally less effective than other off-loading modalities, inlay depth shoes and custom insoles offer an acceptable compromise when a patient is too unstable to use a more restrictive off-loading therapy. However, both techniques offer only a fraction of the pressure reduction at the site of ulceration compared with the pressure reduction provided by total contact casts or removable cast boots.4

Pressure ulcers on the heel can be accommodated with pressure-relieving ankle-foot orthoses (PRAFO). Several off-the-shelf products are available that essentially float the heel, eliminating contact with the support surface. However, pressure ulcers on other locations or in patients who are immobile or who have rigid deformities often require a combination of techniques that involve dressings, padding, support surfaces, and turning practices.