The Intrepid Dynamic Exoskeletal Orthosis (IDEO) aids in the return to high function after severe lower-limb injuries. Its design incorporates a carbon fiber footplate, a dynamic posterior strut, and a proximal cuff that work to transfer energy around the foot/ankle/lower limb during gait. The IDEO’s design ensures that the ankle and midfoot are maintained in a comfortable, weight bearing position, enabling users to engage in their activities (including running) without discomfort. The IDEO reduces peak pressures on the forefoot by up to 60 percent, allowing active and retired servicemembers to resume high-level activities after limb salvage operations. The IDEO heel wedge is crucial for improving rollover characteristics by adjusting the footplate, strut stiffness, and heel cushions.
A key component to IDEO treatment success is tuning heel cushion stiffness to manage the transition from swing to stance. This has traditionally been done with Kingsley foam, but the production of this foam has been discontinued. To address the pressing need to find a replacement, my colleagues and I evaluated different types of FlexFoam for stiffness and durability.
The FlexFoam system from Smooth-On is a two-part solution that is nontoxic and can easily be poured and cured into the desired shape. Our objective was to find a replacement foam that could replicate the specific characteristics of the Kingsley Heel Cushion Material (Kingsley Manufacturing Co., Costa Mesa, CA), both in its soft (durometer=44, stiffness=5 N/mm) and firm (durometer=78, stiffness=59 N/mm) wedge forms.
Our findings revealed that the FlexFoam-iT IV Tuff Stuff (durometer=53, stiffness=5.1 N/mm) and FlexFoam-iT 15 Tuff Stuff (durometer=51, stiffness=6.0 N/mm) were suitable replacements for the Kingsley Soft heel cushion foam.
When subjected to 80,000 cycles in a cyclic testing machine to simulate gait, the FlexFoam solutions exhibited less deformation than the Kingsley foams. As a result, the FlexFoam IV Tuff Stuff will be used to replace the Kingsley soft foam. Additionally, we used the data we collected from the testing to select a medium foam, which will be made of the FlexFoam-iT 17 (durometer=64.52, stiffness=18.70 N/mm). However, we could not identify a suitable replacement for the firm foam. Further research and testing will be necessary to find a comparable alternative for this specific type of foam.
Our future work will focus on finding a suitable alternative to Kingsley Firm foam and improving the manufacturing process of FlexFoam heel wedges within our prosthetic clinic. The FlexFoam line from Smooth-On is an option that can be easily shaped into a heel wedge using standard equipment found in O&P fabrication facilities. With this solution, we can continue IDEO treatments when a medium or soft heel wedge is needed while we look for other solutions for the firmer foams.
Julia Marielle Castrucci is a researcher at the Center for the Intrepid, Extremity Trauma and Amputation Center of Excellence, and the Oak Ridge Institute for Science and Education. She can be contacted at [email protected].
Disclaimer: The views expressed herein reflect the results of research conducted by the author and do not reflect the official policy or position of the Brooke Army Medical Center, the Defense Health Agency, the Department of Defense, or any agencies under the US government.
