Össur and OECHSLER use Carbon Technology to Produce Better Prosthetic Feet

Prosthetic limbs have come a long way in providing better comfort, fit, and performance, thanks to innovative technology like elevated vacuum systems. Using Carbon’s specialized materials and Digital Light Synthesis™ printer technology, Össur, and partner OECHSLER, were able to iterate designs quickly for their new prosthetic models. Össur’s Pro-Flex® ST Unity is a prosthetic foot featuring an active vacuum pump, which stabilizes the residual limb while improving circulation and reducing movement. The Pro-Flex® Terra offers a user-removable wedge, also produced with Carbon’s technology, allowing for customizable heel stiffness and enhanced performance on varied terrain. These advancements highlight how additive manufacturing improves the user experience in prosthetic design.

Pro-Flex ST Unity Vacuum Pump Bumper

Elevated vacuum control systems include a liner, suspension sleeve, and air evacuation pump. Residual limbs vary in volume throughout the day, so these systems help manage that volume and improve the fit of prosthetic limbs by creating a vacuum between the liner and socket wall. This vacuum can improve comfort, mobility, and transfers, as well as balance and stability. It can also reduce the risk of falls, improve gait symmetry, control volume, and reduce fluctuations.

The Pro-Flex® ST Unity is a prosthetic foot with an integrated active vacuum pump. Where the pump meets the top blade of the prosthetic foot is a pump bumper, which cushions against the top blade of the prosthetic foot with each step.

Pro Flex ST Unity prosthetic foot with integrated active vacuum pump
Figure 1. Pro-Flex ST Unity prosthetic foot with integrated active vacuum pump featuring a bumper

Pro-Flex Terra Wedge

Wedges in prosthetic feet are one tool for fine-tuning the alignment and performance of artificial limbs. They adjust the stiffness of the heel or toe, affecting how the foot responds to uneven terrain and the user’s center of gravity.

The Pro-Flex® Terra is Össur’s latest prosthetic foot offering and utilizes Carbon technology to create a user-removable wedge. The wedge increases heel stiffness and reduces plantar flexion. The high durability of Carbon’s EPU 41, combined with the flexibility of additive manufacturing, allowed Össur to fine-tune the stiffness properties, offer three different stiffness responses depending on the ankle joint motion, and add damping to the heel strike. Össur adjusted design details for assembly and usability, taking full advantage of the benefits of 3D printing. Because of Carbon’s technology, Össur could tailor the design so the wedge could be inserted by hand, but still provide good seating so it would not fall out while in use.

Pro-Flex Terra Wedge Option
Figure 2. Pro-Flex Terra Wedge Option

A Production Partnership with OECHSLER

Össur started to work with OECHSLER, a Carbon Production Network Partner, on the development of the 3D printed design. Given that OECHSLER is one of the leading companies working with Carbon technology, it was a natural choice for them to apply Carbon DLS technology to the Össur project. The challenge was to find a material that provides better damping mechanics for a more realistic walking experience. OECHSLER covered the entire development chain, including material testing and selection, lattice design, and product development. After achieving improved characteristics, Össur brought this product into series production. Following extensive development and industrialization, the product is now being manufactured in series by OECHSLER in Germany and is available in the market.

The biggest value Össur found in using the Carbon platform is the ability to quickly iterate on the materials and design as design issues emerge during testing. Össur devices undergo rigorous testing, including a full lifecycle test for more than 2 million overloading steps. The devices are also waterproof, and all the components are subjected to stringent environmental testing.

“Our goal is to prioritize user satisfaction as the central element in our design process. Therefore, user feedback plays a crucial role in driving our designs. We typically adopt an iterative approach, combining mechanical testing with clinical trials.”
Felix Starker Product designer – Feet Technology, Össur

Reducing the time to market is always a priority for Össur. Once verification testing was completed and the design was finalized, parts were rapidly manufactured and ready for assembly. This eliminated the need to wait for final tool design and manufacturing, which typically constitutes a significant portion of a development project’s timeline. Importantly, the parts tested during the design phase were identical to the production parts. The fast transition from verification to manufacturing allowed Össur more time to iterate and improve on the design.

Conclusion

The Pro-Flex® ST Unity and Pro-Flex® Terra showcase how additive manufacturing enhances functionality, fit, and user experience. By leveraging the flexibility and precision of 3D printing, Össur has been able to quickly iterate designs, ensure high-quality standards, and bring innovative solutions to market faster. This partnership highlights the potential for cutting-edge technology to transform prosthetic limb development to realize Össur’s mission of Life Without Limitations.