Dennis Janisse, C. Ped.
Medical College of Wisconsin / National Pedorthic Services, Inc.
Milwaukee, Wisconsin
The charcot foot accounts for a small percent of the diabetic foot complications, but presents some of the most challenging scenarios for management. Charcot changes can occur in the forefoot, mid-foot, hind-foot and ankle. Probably some of the most significant deformities occur in the mid-foot resulting in medial and/or lateral displacement/collapse or a rocker bottom foot. These deformities can be flexible or rigid, often as a result of the management of the charcot foot during its acute and coalescent stages.
Viscoelastic polymers have been used extensively in foot orthoses for years, but they can be extremely useful for shoe modifications as well. Viscoelastic polymer is available in pre-made devices, insoles, arches, heel cups, etc., in sheet stock, or as a two part component kit to be mixed at the time of use. For shoe modifications, the technicians find the custom mix option to be the most efficient. The viscoelastic polymer can be mixed to provide unlimited densities; it adheres to most surfaces and holds its shape to varying degrees depending on the density.
Viscoelastic Polymer in softer densities can be used to fill excavations of many types in the insoles of shoes. Excavation in the insole and sole of the shoe can provide relief cushioning and protection for distal toe deformities, prominent metatarsal heads, or bony plantar prominence, often due to the charcot deformities, and also relieve or protect ulceration or fragile post ulceration sites. Providing or creating the excavation can be accomplished from the inside of the shoe or externally. Tools used include knives, drills and dremels. After determining the location of relief and removing part of the insole or sole, it can be easily filled with viscoelastic polymer.
Charcot foot deformities are often managed with custom shoes, which can be costly, time consuming and often not well accepted by the patient. Re-lasting or reshaping the insole of shoes can be an option for many (not all) feet with charcot deformity. The most common site for the relasting process is in the mid-foot area of the shoe to match the shoe shape to the foot shape. Relasting can also be accomplished, for example, in the forefoot to relieve pressure on a fixed hallux varus or laterally for a prominent base at the fifth metatarsal. After the area of reshaping is determined, the shoe is cut through the insole and sole, along the medial or lateral border of the shoe, then held open in the new shape with a firm spacer or cementing a temporary insole over the original. A firm density of viscoelastic polymer is then mixed and poured from the bottom of the shoe. After it is set up, the temporary insole in the shoe is removed and an outsole or whatever further shoe modifications that are needed are performed. The re-lasting process doesn't really change the fit of the shoe, as most of the applications are in the mid-foot where there is adjustability due to the lacing system.
As with any pedorthic modality, cautions and break-in must be discussed with your patient-especially with the charcot / diabetes patient, as they probably have less protective sensation.
These modifications can help you provide a functional, protective, ethically acceptable shoe to your at risk patients in a reasonable amount of time.
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