Key Prescription Pearls For Diabetic Orthotics

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Table 1: How To Assess The Foot Risk Categories (FRC)

FRC Protective Threshold Vascular Disease History of Ulcer Orthotic Type
0 WNL WNL WNL Prefabricated
1 Absent WNL WNL Prefabricated
2 Absent Abnormal WNL Custom
3 Absent Abnormal Positive Custom

For the rigid diabetic foot type, you should use softer materials when prescribing orthotics.
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Author(s): 
By Eric M. Feit, DPM, FACFAS and Alona Kashanian, DPM

It is typically easier to heal a diabetic foot ulcer than it is to prevent recurrence. Once you’ve healed the ulcer, the next challenge is to minimize pressure at the site of the old ulceration or the site of a boney prominence. If the patient has never had an ulcer but has a high risk for ulceration, then employing pressure off devices is essential for prevention.
Obviously, the large majority of diabetic foot ulcerations are preventable. There are several keys to prevention, which include organized treatment protocols, early detection, aggressive wound care, orthotics and appropriate shoes. For this column, let’s take a closer look at orthotic management and materials.
Initial diabetic patients should be screened for the risk of ulceration. This includes evaluating their circulation (i.e. pedal pulses, subpapillary venous plexus filling time, and ankle brachial indices if the vascular status is questionable) and their protective threshold via a 5.07 Semmes Weinstein monofilament test. In addition, be sure to check for boney prominences or sites of old ulceration.
Based on this exam, you should be able to classify the patient into a foot risk category, which will help you choose an appropriate orthotic (See Table 1 on page 16). The pre-fab orthotic can be purchased OTC or through a lab. The most common materials are Spenco with an EVA shell and ppt in the forefoot extension. Some labs have a trilaminate of plastazote (two different densities) and one layer of ppt.
Using proper orthotics and shoes will save many feet from unneccesary amputation and infection. You can employ these devices for initial treatment, but it is vital to recognize when these devices are inadequate and when there is a need for surgical intervention in the diabetic patient. It is often necessary to perform surgery first and then utilize orthotics and special shoes for long term foot/limb salvage.
The biomechanics of the foot often increase plantar pressures in the diabetic foot, more so than in the rest of the population.1 This is primarily due to peripheral neuropathy which may result in the diabetic patient being unable to feel abnormal pressure points during gait. This leads to increased motion of the affected joints and subsequently increased shear forces. In a patient with abnormal pronation, there are often higher pressures under the first metatarsal head and medial aspect of the heel, which may lead to ulceration.
The Benefits Of Custom Orthotics
There are several goals of using custom-made orthotics for the diabetic patient. When a high risk patient comes in for his or her initial office evaluation, it is vital to recommend a custom device to help prevent ulceration. Orthotics will help improve ambulation by controlling pronation and minimizing stress on the muscles of the foot and leg. The more a diabetic patient can stay active with walking and exercise, there is less chance for the possibility of other diabetic complications such as heart disease, stroke, kidney disease and eye disease. This is a direct result of improved blood glucose control.
You may also use custom orthotics to treat foot ulcers. Although it is ideal to heal the ulcer first, it may not always be the best thing for the patient. Some patients must stay active and continue to walk in shoes, depending upon their job or general health conditions. We typically recommend waiting until an ulcer is less than 1cm before using an orthotic. If you use an orthotic with an open ulcer, you can place it inside a below knee cam walker for maximal benefit. When it’s absolutely necessary, you may place the orthotic in the shoe.
In our experience, once diabetic patients stop walking, their general health and mental health quickly deteriorate. Having a foot ulceration for several months or years has a tremendous effect on their quality of life and morale. Therefore, prior to utilizing an orthotic for an open ulcer, we typically employ a total contact cast or felt to foam dressing with an aperture to offload the ulcer. Once the ulcer is healed or less than 1 cm, then we dispense the orthotic.

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