Ankle-foot prosthesis for automatic adaptation to sloped walking surfaces
Inventors
Hansen, Andrew H. • Nickel, Eric A.
Assignees
US Department of Veterans Affairs • University of Minnesota System
Publication Number
US-10376388-B2
Publication Date
2019-08-13
Expiration Date
2033-09-10
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Abstract
An ankle-foot prosthesis includes a foot plate, an ankle frame attached to the foot plate, a yoke pivotally connected to the ankle frame and including a member for attaching to a leg, a damper having a first end connected to the yoke and a second end connected to the ankle frame, and a control mechanism for switching the damper between low and high settings.
Core Innovation
The invention is directed to an ankle-foot prosthesis that automatically adapts to level as well as sloped walking surfaces, allowing lower limb amputees to walk over various sloped terrain more easily and safely, while also providing more stability during standing and swaying tasks. The prosthesis includes a foot plate, an ankle frame attached to the foot plate, a yoke pivotally connected to the ankle frame with a member for attaching to a leg, a damper connected between the yoke and the ankle frame, and a control mechanism for switching the damper between low and high settings.
The background identifies the problem that most currently available prosthetic ankle devices operate about one equilibrium point and struggle to provide stable walking on sloped surfaces, often causing instabilities. Existing systems using hydraulic dampers, microprocessor controls, or powered motors either lose energy, require multiple steps to adapt, need large power sources, or are expensive and impractical for many users. There is a need for a prosthesis that can adapt to different sloped surfaces on each step without heavy power demands or complex systems.
The invention solves this by providing a prosthesis whose damper has switchable damping levels controlled by a microprocessor or mechanically, which maintains a high extension damping during foot flat and rolling over to achieve a biomimetic ankle-foot roll-over shape, then switches to low extension damping to allow the ankle to return to neutral during swing phase, enabling adaptation on every step. It also features a stable mode with high damping for standing tasks and includes a neutralizing spring in parallel to the damper. Various embodiments of the fluid control circuit for controlling the damper's compression and extension and different configurations of the ankle frame, yoke, damper, and stiffness members are disclosed.
Claims Coverage
The patent presents one independent claim encompassing the main inventive features of the ankle-foot prosthesis.
Hydraulic ankle-foot prosthesis structure
An ankle-foot prosthesis comprising a foot plate with rear and forward deflectable portions, an ankle frame with anterior, posterior, and apex portions, a yoke pivotally connected to the apex, and a hydraulic damper pivotally connected between the front end of the yoke and posterior portion of the ankle frame.
Inclusion of a stiffness member in parallel with the damper
A stiffness member, such as a spring or elastic member, is disposed in parallel to the hydraulic damper to provide elastic response and contribute to ankle mechanics.
Fluid control circuit for damper control
A fluid control circuit is provided to control extension and compression of the hydraulic damper. It includes cutoff valves and may have check valves and variable fluid-flow resistors to adjust hydraulic fluid resistance particularly in plantarflexion.
Roll-over surface limiting dorsiflexion
The anterior portion of the ankle frame has a curved, upwardly inclined surface forming a roll-over surface that limits dorsiflexion deflection of the forward portion of the foot plate by direct engagement.
These inventive features collectively provide an ankle-foot prosthesis that automatically adapts to sloped walking surfaces by controlling damping dynamically, improving gait stability and comfort, and offering configurations facilitating customization and efficient biomechanical performance.
Stated Advantages
Allows for more natural, comfortable gait for users.
Improves energy efficiency during walking and other gait activities.
Simple design with fewer components leading to low maintenance requirements.
Compact and durable construction reduces rate of failure compared to more complex systems.
Prevents undesirable backward swing to avoid imbalance or injury.
Quieter, lightweight, and less clumsy, enhancing user-friendliness.
Automatically adapts to different sloped walking surfaces on each step.
Switches to a stable mode for standing or swaying tasks, improving stability.
Documented Applications
Use by lower limb amputees for walking on level and sloped surfaces with improved stability and confidence.
Use during standing and swaying tasks such as washing dishes, where a stable mode is beneficial.
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