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Orthotic Shell Materials

At the heart of every custom orthotic is the orthotic shell! Shells are the primary factor in deciding not only an orthotic's comfort level, but the level of support and correction as well.

The most common materials used in making orthotic shells are thermoplastics and elastomers. These materials are preferred for their versatility, ease of customization, and durability.

  • Thermoplastics: Materials like Polypropylene, Nylon and HMW plastics are used in orthotics due to their rigidity and moldability. Orthotics made from these materials are relatively lightweight, have good mechanical control properties, and provide good support for various foot conditions.

  • Elastomers: EVA, Poron and Cork are rubber/foam-like materials often used as an alternative to thermoplastics. They offer excellent shock absorption, flexibility, and cushioning properties, making them suitable for orthotics designed to address comfort and pressure relief.

Orthotic shells made from these materials can be easily customized and molded to fit the patient's foot anatomy, offering proper support and correcting bio-mechanical issues. We'll be going over the most popular material of each type.

Polypropylene (PP):

Polypropylene is the most widely used thermoplastic material. It is relatively rigid, providing excellent support for the foot and helping to control excessive motion or pronation. Heating and molding polypropylene to the patient's foot shape is an easy process, allowing for a highly personalized fit and correction of specific bio-mechanical problems.

Orthotic devices made from polypropylene are generally lightweight, making them comfortable for everyday use. It’s a very sturdy material, ensuring the orthotics can withstand regular wear and tear.

A disadvantage of polypropylene orthotics is that they can be somewhat bulkier, which may not be ideal for certain footwear styles. This material is thick throughout the entire orthotic and doesn’t provide much shock absorption without adding other padding materials like Poron. Finally, Polypropylene also tends to flatten and is prone to cracking which has led to it falling out of favor with many podiatrists.

Ethylene-Vinyl Acetate (EVA):

EVA is an elastomer material known for its exceptional shock absorption and cushioning properties. It is lighter and more flexible than polypropylene and meant to provide added comfort to the wearer.

Orthotics made with EVA are suitable for use in various shoe types, including athletic and dress shoes. While not as rigid, EVA still offers adequate support and can help alleviate pain while addressing certain foot conditions.

The main disadvantage of EVA is that it wears out faster due to its softer nature, especially in high-impact situations. EVA orthotics also tend to collapse under the foot over time which decreases its effectiveness in controlling severe pronation or providing substantial arch support.

Performance RX®:

Forward Motion Medical's founding goal was to create a slim, sturdy device that fits any shoe and can be molded to the patient's foot. The result is our standout product: Performance RX® orthotic shells. Made of a proprietary blend of Engineered Nylon, PRX shells are strong and heat-moldable.

Custom orthotics made with PRX shells are five times stronger than polypropylene and made in a special way that varies its thickness. This allows the orthotics to be thick in areas like the arch and only 1.7mm thin in contact point areas.

Every orthotic made with a PRX shell comes with a lifetime guarantee to never break, change shape or flatten (unlike polypropylene). Shells come in 4 different rigidities for doctors to choose from so that you can provide the maximum benefit and comfort for your patients while still being thinner, lighter, and more controlled than other orthotic materials.

PRX Graphite®

PRX Graphite® is a free upgrade we offer that combines our engineered nylon with carbon fiber for extra rigidity and firmness. Our patented manufacturing process allows the carbon to be molded and shaped as a whole within the shell (similar to how rebar is put in cement). This strengthens the shells without compromising its structure and becoming brittle like other graphites on the market that use carbon fragments.

Forward Motion PRX Graphite shells allow orthotics easily fit into any type of shoe while still providing a high strength-to-weight ratio. PRX Graphite is recommended for high-impact sports like running and great for high-performance patients and athletes. It's unique design is what sets our custom orthotics apart from the rest of the industry.


Whatever material you want for your patients, or whatever they need in a custom orthotic, we got them covered at Forward Motion Medical! If you have any questions, please feel free to contact us. We make orthotics that your parents will love to wear!

Give our Performance RX™ custom orthotics a try today. We don't charge any extra to make any materials.

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