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Options for Off-Loading the Diabetic Foot

Lavery, Lawrence A. DPM, MPH; Baranoski, Sharon MSN, RN, CWOCN, APN, FAAN; Ayello, Elizabeth A. PhD, RN, APRN,BC, CWOCN, FAAN

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Advances in Skin & Wound Care: May 2004 - Volume 17 - Issue 4 - p 181-186

Reduction of pressure and shear forces on the foot may be the single most important—and most neglected—aspect of treating neuropathic ulceration. Off-loading therapy is a key part of the treatment plan for diabetic foot ulcers. The goal is to off-load (reduce) the pressure at the ulcer while keeping the patient ambulatory. 1-3

Calhoun and colleagues 4 have defined off-loading as “any measure to eliminate abnormal pressure points to promote healing or prevent recurrence of diabetic foot ulcers.” Several methods are available to protect the foot from abnormal pressures (Table 1). Off-loading strategies must be tailored to the age, strength, activity, and home environment of the patient. In general, however, more restrictive off-loading approaches will result in less activity and better wound healing.

Table 1
Table 1:
OFF-LOADING MODALITIES AND WOUND HEALING

Education is critical to improve adherence to off-loading. The patient must understand that the wound is a result of repetitive pressure, and that every unprotected step is literally tearing the wound apart.

OFF-LOADING TECHNIQUES

Methods of off-loading the foot include total contact casting (TCC), removable walking boots, healing sandals, half-shoes, and ankle-foot orthoses.

Total contact casting

Considered the gold standard for off-loading the foot, TCC reduces pressure at the ulcer site while allowing the patient to remain ambulatory. 3,4 A skilled clinician is required to apply the molded plaster cast to ensure a proper fit. A TCC is a modification of a traditional fracture cast with minimum cast padding and a covering to protect the toes. The cast is molded to the contour of the foot and leg so that the foot and leg cannot move within the cast (Figure 1). TCCs are generally changed every 1 to 2 weeks, but in patients with edema or other concerns, the cast may need to be replaced more frequently.

Figure 1
Figure 1:
APPLYING A TOTAL CONTACT CAST

TCC is one of the most effective ways of treating plantar neuropathic foot ulcers described in the medical literature. 3,6 Studies 5-12 have shown that TCC can heal these ulcers in 6 to 8 weeks.The proportion of wounds that heal in descriptive and randomized clinical trials with TCC is consistently much higher than those using topical growth factors, bioengineered tissue, or special dressings. 13-16

One of the main advantages of using a TCC is that it forces the patient to adhere to off-loading. The ulcer is protected with every step the patient takes, around the clock. Using TCC to facilitate wound healing is analogous to using a fracture cast to heal a fracture—in both cases, healing is facilitated by rest and immobilization. TCC reduces the patient’s activity level, 9 decreases stride length and cadence, and significantly reduces pressure at the ulcer site. 3,6 The main disadvantages for patients are the same as their complaints with a fracture cast—the cast is heavy and hot, and makes bathing, walking, and sleeping difficult.

Removable walkers

A number of removable walking boots are available to help protect and heal foot wounds in patients with diabetes, including the DH Pressure Relief Walker, the Conformer Boot, and the AirCast Pneumatic Walker. Removable walking boots offer several advantages over TCCs: They are relatively inexpensive, they have a protective inner sole that can be easily replaced if it shows signs of wear, they do not require special training for correct and safe application, and they can be easily removed to assess and debride the wound. 6,9

The DH Pressure Relief Walker has been shown to be identical to TCCs in pressure reduction at the site of ulcerations on the sole. 6 The disadvantage to these boots is that patients can remove them, so the element of forced adherence that makes the TCC attractive is lost.

Healing sandals and half-shoes

These products are designed to reduce pressure on the forefoot. They are useful for patients who cannot tolerate a TCC or for those who need a transitional device after removal of a TCC while awaiting therapeutic shoes and insoles. The DH Healing Sandal is a convenient product with hook-and-loop closures, a conforming cover for the forefoot, and a patented pressure-reducing insole. Other types of healing sandals require a pressure-reducing insole added in the office.

Half-shoes, such as the OrthoWedge or Darco products, were originally designed to protect the forefoot after elective surgery. The OrthoWedge shoe has a 1½-inch (4-cm) heel wedge at a 10-degree dorsiflexion angle, so that weight is removed from the forefoot area. Studies by Needleman 17 and Lair 18 provide support for its role in postoperative patients following surgery on the forefoot. However, these types of shoes are not well accepted by patients because they are difficult to walk in. They typically cause pain in the contralateral extremity, and patients with postural instability cannot safely use them.

In a randomized clinical trial that compared TCCs with healing sandals and removable cast boots, patients in the healing sandal group used the device during walking significantly less often than subjects in the TCC group. 9,19

Ankle-foot orthoses

Custom-made ankle-foot orthoses can be used for lower-extremity pathology, including Charcot fractures, tendon injuries, and neuropathic ulcers. The Charcot Restraint Orthotic Walker (CROW), for example, was initially described to treat patients with neuropathic fractures. It provides protection to the neuropathic foot and aids in controlling lower-extremity edema. This device looks like a ski boot; it has a rigid polypropylene shell with a rocker bottom sole. 19

The primary drawback to custom-made devices is cost, typically about $1000. If the structure of the foot changes or local edema resolves, the device can no longer be used. Because a number of less expensive, off-the-shelf products are now available to treat neuropathic wounds, custom ankle-foot orthoses are used less frequently. Off-the-shelf devices should be replaced at regular intervals because the materials in the insoles will lose their effectiveness over time. 20

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