Adaptable Ankle-Foot Prosthesis
INVENTION: The Adaptable Ankle-Foot Prosthesis automatically adapts to different surface slopes and to shoes of different heel heights. Current prosthetic ankle-foot mechanisms cannot automatically adapt to these conditions on the first step. Unlike current prosthetic ankle-foot mechanisms, the Adaptable Ankle-Foot Prosthesis:
Automatically adapts to changing slopes on the first step
Automatically adapts to different heel heights
Mimics the able-bodied ankle-foot mechanism in the period from opposite heel contact to toe off
May enable faster walking and reduce the amount of energy needed for walking Current prosthetic and orthotic ankle-foot mechanisms allow rotational motion about a single equilibrium point that does not change without mechanical adjustments. This single and fixed equilibrium point can result in good function on level ground and when using shoes of one particular heel height. However, problems can arise when walking on different slopes or when using shoes of different heel height. The heel height problem can be fixed using a change in the alignment of the prosthesis. However, this adjustment does not happen automatically in current devices.
The Adaptable Ankle-Foot Prosthesis utilizes stiffness properties that mimic the natural behavior of an able-bodied foot and ankle. It more closely mimics the able-bodied foot and ankle in the period from opposite heel contact to toe off because it automatically plantarflexes beyond a neutral position during this unloading phase of gait. The Adaptable Ankle-Foot Prosthesis also brings the ankle back into a neutral or slightly dorsiflexed position just after toe off to provide toe clearance during the swing phase. The plantarflexion beyond neutral position at late stance may reduce the amount of energy needed for walking for individuals using the devices by increasing the return of stored energy to the leg. This feature may in turn help prosthesis and orthosis users to walk at consistently faster speeds.
Three prototypes have been designed and constructed. The prototypes are simple in design; no electrical or active components are utilized.
Northwestern University seeks a licensing partner to commercialize this invention. A patent application has been filed.
Andrew Hansen, Steven Gard, Dudley Childress, Brian Ruhe, Ryan Williams
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