Further improvements to ankle-foot prosthesis and orthosis capable of automatic adaptation to sloped walking surfaces

Inventors

Hansen, Andrew H. • Nickel, Eric A.

Assignees

US Department of Veterans Affairs

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 an improved ankle-foot prosthetic and orthotic system that is capable of automatic adaptation to sloped walking surfaces without the need for powered devices, motors, or batteries. This system mechanically adapts the torque moment based on motion, inclination extent, and surface topography through a passive mechanism. It features self-adapting ankle units combined with other mechanical elements that emulate the gait of able-bodied individuals and automatically adjust to different terrains and slopes on every step. The system uses stiffness-based control and few or no sensing devices, enabling energy storage and release properties, which offer efficient walking dynamics similar to a natural ankle-foot system.

The problem being solved addresses the limitations of current prosthetic and orthotic ankle-foot devices, which either lack ankle motion or maintain a constant equilibrium point that does not adapt automatically to different terrains or heel heights. Existing devices typically rely on damping control, which dissipates energy, or require user adjustments and do not adapt instantaneously to rapidly changing slopes. Some available adaptive devices use sensors and motors but suffer from delayed adaptation timing, incremental adjustments over multiple steps, complexity, weight, or cost. Hence, there remains a need for a passive, lightweight, mechanically simple device that can biomimetically adapt the ankle-foot roll-over shape and equilibrium point at each step without energy loss common to damping-based designs.

This invention introduces a system comprising first and second torsion means (stiffness elements), an engagement means such as a clutch, and an arrangement where these elements are in series or parallel combinations that allow switching between low and high stiffness states during gait. The system includes bumpers of differing stiffness to modulate resistance during plantarflexion and dorsiflexion, an engagement mechanism that engages upon loading (e.g., a wrap spring clutch operated via a shock-absorbing pylon and linkage), and disengages upon unloading, thereby adjusting the effective ankle stiffness and equilibrium point according to surface slope with every step. The design enables a plantarflexion-dorsiflexion range from approximately 80° plantarflexion to 45° dorsiflexion and supports energy-efficient gait that closely approximates biomimetic ankle function.

Claims Coverage

The independent claims cover two main inventive features regarding passive, self-adapting ankle-foot prosthetic and orthotic systems with specific structural and functional components.

The claims define a passive ankle-foot prosthetic and orthotic system that uses load-responsive engagement of a spring clutch mechanism and differential stiffness bumpers arranged between distinct structural elements to provide automatic adaptation to surface slopes by modulating ankle dorsiflexion resistance and restoring foot neutral position when unloaded.

Stated Advantages

Documented Applications