Passive ankle-foot prosthesis and orthosis capable of automatic adaptation to sloped walking surfaces and method of use
Inventors
Hansen, Andrew H. • Sensinger, Jonathon W.
Assignees
Northwestern University • Rehabilitation Institute of Chicago • US Department of Veterans Affairs
Publication Number
US-8480760-B2
Publication Date
2013-07-09
Expiration Date
2031-04-12
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Abstract
The present invention relates to an improved system for use in rehabilitation and/or physical therapy for the treatment of injury or disease to the lower limbs or extremities. The system can enable an amputee to proceed over any inclined or declined surface without overbalancing. The system is mechanically passive in that it does not utilize motors, force generating devices, batteries, or powered sources that may add undesirable weight or mass and that may require recharging. In particular the system is self-adapting to adjust the torque moment depending upon the motion, the extent of inclination, and the surface topography. An additional advantage of the improvement is that the system can be light and may also be simple to manufacture.
Core Innovation
The invention provides improved ankle-foot prosthetic and orthotic systems that enable the gait of an individual using the device to emulate the gait of an able-bodied individual. These systems automatically adapt the gait to different terrains and slopes on each step and are mechanically passive, not requiring motors, powered devices, or batteries.
The system addresses the problem that many current prosthetic and orthotic ankle-foot devices do not allow ankle motion or only allow rotational motion about a single equilibrium point, which does not change without mechanical adjustments. This causes difficulties when walking on varied terrains or using shoes with different heel heights, as current devices cannot automatically adapt to these changing conditions.
The invention overcomes these limitations by providing a self-adapting ankle-foot device that uses stiffness-based control with two sets of springs—a neutralizing spring and a larger triceps surae spring—and a cam clutch system. This arrangement allows the device to automatically adjust the equilibrium point, enabling adaptation to surface inclinations and shoe heel height during walking, while also providing energy storage and return. Improvements include a simpler, lighter hinge activation element, an improved cam assembly nested within a main cam for compactness and durability, and in-line placement of neutralizing elements and cam clutch to reduce the ankle size.
Claims Coverage
This patent includes two independent claims that define inventive features relating to an improved adaptive ankle-foot prosthesis and its structural components.
Improved passive adaptive ankle-foot prosthesis structure
The prosthesis comprises a footplate with anterior and posterior portions, a housing pivotally connected to the footplate, a first cam connected to the footplate, and a second cam for engagement arranged as a cam clutch system with a bracket fixedly attached to the second cam and affixed to a leg attachment means. The posterior footplate includes an aperture confining at least one neutralizing element connected to a spacer and housing, and a torsion member associated with the footplate.
Integration of spring elements and cam assembly for ankle joint control
The prosthesis includes a triceps surae spring biasing the footplate toward plantarflexion, an ankle frame pivotally connected to the footplate, a neutralizing spring biasing the ankle frame to a neutral position, a main cam secured to the footplate engaging with the triceps surae spring, a pylon pivotally secured to the ankle frame with a drive cam mounted for engagement, and a hinge spring biased to disengage the drive cam from the main cam.
The independent claims cover the mechanical design of a passive adaptive ankle-foot prosthesis featuring a cam clutch system, neutralizing and triceps surae springs, and a pivotally connected housing and footplate allowing automatic adaptation to various walking conditions.
Stated Advantages
The system can automatically adapt to inclined or declined surfaces without overbalancing.
It is mechanically passive, requiring no motors, batteries, or powered sources, thereby avoiding added weight or mass and eliminating recharging needs.
The design is light and simple to manufacture compared to prior art devices.
The cam assembly is reduced in size and designed for quieter operation and more durability.
The in-line arrangement of neutralizing elements and cam clutch allows a thinner outer housing and reduced overall ankle size and thickness.
The system stores and returns energy efficiently through stiffness-based control rather than damping control, allowing a biomimetic ankle-foot rollover shape and plantarflexion at late stance.
Documented Applications
Use in rehabilitation and physical therapy for treatment of injury or disease to the lower limbs or extremities.
Ankle-foot prostheses and orthoses for persons with disabilities, improving mobility and balance on various walking surfaces.
Use with patients to automatically adapt gait to different terrain gradients and shoe heel heights.
Potential applications in walking machines, legged robots, and toys.
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