Choosing the right material for a custom foot orthotic depends on a few key factors, including the patient’s condition, activity level, footwear, and personal comfort preferences.The basic structure of a custom foot orthotic device is referred to as the “frame”or alternatively “shell”. Frames can vary by rigidity, thickness, depth, width and material. The effectiveness of your orthotic therapy will be enhanced by pairing the proper frame material with the objective of treatment. A general guideline is to use a softer material for a rigid foot, and a more rigid material for a flexible foot. Of course, there are many exceptions to this guideline, and you should consider every case as unique unto itself.
The listing of frame material choices can be found in the configurator in the Foot ID Pro app, or at the top of the KevinRoot Medical website home page. A summary of the choices follows:
- Polypropylene - this is the workhorse material used in the manufacture of foot orthotics. Initially used to replace plexiglass (Rohadur) in the early days of Root type orthotic devices. A very durable and easily adjusted material, can be made in many configurations suitable for a wide variety of applications. Very few times it wouldn't be a good choice, in some form, for a frame material.
- Subortholene - like Polypro, but generally softer and susceptible to distortion over time. Generally to be used when flexibility and comfort are to be emphasized. Can be used to reinforce an accommodative device in a patient who cannot tolerate much motion control.
- Carbon (XT) and Carbon Graphite (TL-2100)- High tech material used indicated when space inside the shoe or boot is limited. XT is a good choice for women’s dress shoes, slip on shoes, but can give too much in heavier patients. TL-2100 is used in rigid boot applications such as ski boots and skates. Always inspect devices periodically for cracking or fatigue.
- EVA - available in a variety of rigidity properties and thicknesses. Great choice if shock absorption is a priority such as a rigid cavus foot type.
Alternative materials may be available such as thermocork, leather, celucyte, or HDPE, if preferred. Frame material selection is crucial in determining the effectiveness of your orthotic devices. When in doubt, Polypro is often a good choice due to its versatility and durability.
Generally speaking, in flat feet/overpronation conditions a rigid or semi-rigid material (like carbon fiber or polypropylene) will provide strong motion control and arch support. In a case of high arches/supination, softer, more accommodative materials (like EVA or cork) to offer shock absorption and pressure redistribution. In diabetes/neuropathy, soft, multi-layered materials (e.g., plastazote, poron) are indicated to reduce pressure and prevent ulceration.
When treating athletes and active individuals durable and slightly flexible materials like polypropylene or carbon composites, often combined with shock-absorbing top covers, will work the best. In sedentary and elderly patients, comfort-focused materials, such as cork and leather, soft EVA or plastazote, with full contact and pressure relief.
Considering footwear type, in dress shoes for both men and women, slim, low-profile materials like thin polypropylene or graphite are advisable. Athletic shoes or boots with removable inserts can accommodate thicker, multi-layered full length orthotic devices. Sandals and open shoes: require special design considerations, carbon graphite, heat-molded EVA or cork-based materials for aesthetic blending.
In summary, it is always crucial to consider durability vs. comfort. More durable materials are: polypropylene, subortholene, carbon fiber, graphite offering long-lasting, enhanced support.
More Comfortable materials are: EVA, plastazote, and cork offering better cushioning but may wear faster.
