ORLANDO, Fla. — Materials, reinforcement technique and heat treatment impact the mechanical properties of solid ankle foot orthoses, according to a preliminary report presented by Thranhardt Lecture finalists Gary Bedard, CO, FAAOP and Fan Gao, PhD, at the American Academy of Orthotists and Prosthetists Annual Meeting and Scientific Symposium, here.

Bedard said although polypropylene has been the go-to material for constructing solid ankle foot orthoses (SAFOs) for 50 years, little has been done to enhance it.

Their study examined copolymer polypropylene, homopolymer polypropylene and carbon-infused polypropylene in fashioning a variety of eight SAFOs.

Carbon-infused polypropylene is a proprietary material, Bedard said.

Gary Bedard


“It takes discontinuous fibers and embeds it as a discrete core within polypropylene. All the pre-pregs we have available at this point use continuous fibers. The discontinuous fibers give it the element to be able to mold and fold like a sheet material. That is the advent for use in this field. It will take pretty much any shape you want.

“Adding carbon fiber to it in this discontinuous form makes it what the FDA likes to call predicated material. We know carbon fiber, we know polypropylene, put it together and it gives you a predictable outcome,” Bedard said.

Bedard and Foo also used annealing, or cold tooling, to craft their SAFOs.

“That shock stops the reformation of the materials. You ramp up your temperature, monitor it with a direct thermocouple going inside the oven, heating it to plateau and then ramping it down. This is a multi-hour process.”  

Study results showed carbon infused homopolymer polypropylene outperformed the other two popularly used polypropylenes. Results also showed stiffness at prescribed resistance torque and on both loading and unloading curves.

Compcore reinforcement technique was more favored than corrugated reinforcement technique, Foo said, while annealing showed promising effects on improving the mechanical properties of homopolymer polypropylene SAFOs.

For more information:

Bedard G. Paper TL4. Presented at: American Academy of Orthotists and Prosthetists Annual Meeting and Scientific Symposium. Feb. 20-23, 2013. Orlando, Fla.

Disclosure: Bedard and Foo have no relevant financial disclosures.

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