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EP-4734885-A1 - SYSTEMS AND METHODS FOR AN ARTICULATING PROSTHETIC JOINT

EP4734885A1EP 4734885 A1EP4734885 A1EP 4734885A1EP-4734885-A1

Abstract

Prosthetic joints are disclosed such as an ankle-foot prosthesis. An extendable link of a prosthetic device may lengthen or shorten to bring about flexion and extension. The extendable link may include a hydraulic cylinder configured to provide a flexion damping resistance and an extension damping resistance. The extendable link may further include a spring arranged in parallel with the hydraulic cylinder. The spring biases the rotation of the joint. The spring may be a gas spring. The spring may be inside of a piston assembly of the hydraulic cylinder and act directly on hydraulic fluid. In the context of an ankle-foot prosthesis, the spring may be configured to overcome hydraulic resistance to dorsiflexion rotation.

Inventors

  • JACOBS, GREGORY

Assignees

  • Otto Bock HealthCare, LP

Dates

Publication Date
20260506
Application Date
20240628

Claims (20)

  1. 1. An ankle-foot prosthesis, comprising an ankle assembly comprising a prosthetic adapter, an extendable link rotatably attached to the prosthetic adapter to define a first pivot point, and a base rotatably attached to the prosthetic adapter to define a second pivot point and rotatably attached to the extendable link to define a third pivot point; and a foot spring or foot spring assembly attached to the base and configured to work in series with the ankle assembly, wherein the extendable link comprises a hydraulic cylinder configured to provide a dorsiflexion damping resistance and a plantarflexion damping resistance, and a spring arranged in parallel with the hydraulic cylinder, wherein the spring is a biasing gas spring.
  2. 2. The ankle-foot prosthesis of claim 1, wherein the spring is configured to release sufficient energy during any dorsiflexion rotation of the ankle assembly to equal or exceed energy loss from the dorsiflexion damping resistance.
  3. 3. The ankle-foot prosthesis of claim 1, wherein while the foot spring or foot spring assembly is subject to a ground reaction force and the ankle assembly rotates in a dorsiflexion direction, the spring is configured to release sufficient energy to equal or exceed energy loss from the dorsiflexion damping resistance.
  4. 4. The ankle-foot prosthesis of claim 1, wherein the prosthetic adapter, the hydraulic cylinder, and the base define a force triangle that defines an axis of rotation of the foot spring or foot spring assembly about the prosthetic adapter, wherein the spring creates a dorsiflexion biasing moment about the axis of rotation.
  5. 5. The ankle-foot prosthesis of claim 4, wherein the dorsiflexion biasing moment from the spring is always at least 3 Nm.
  6. 6. The ankle-foot prosthesis of claim 1, wherein the spring comprises a gas cavity containing one or more gases at a minimum pressure of 200-1000 psi.
  7. 7. The ankle-foot prosthesis of claim 1, wherein the dorsiflexion biasing moment from the spring at a standing position is 0.05-0.20 Nm/kg body weight.
  8. 8. The ankle-foot prosthesis of claim 1, wherein the dorsiflexion biasing moment at 12° of plantarflexion is 0.15-0.28 Nm/kg body weight.
  9. 9. The ankle-foot prosthesis of claim 1, wherein the prosthetic adapter, the hydraulic cylinder, and the base define a force triangle that defines an axis of rotation of the spring assembly and base about the prosthetic adapter, wherein the axis of rotation is positioned below and in line with a center of mass of a user when the user is in a standing position.
  10. 10. The ankle-foot prosthesis of claim 1, wherein the base defines a foot pivot axis, wherein the hydraulic cylinder defines a hydraulic cylinder axis between the first pivot point and the third pivot point, wherein a moment arm distance between the hydraulic cylinder axis and the foot pivot axis is greater than 25 millimeters (mm).
  11. 11. The ankle-foot prosthesis of claim 1, wherein the spring is arranged to be compressed by hydraulic fluid of the hydraulic cylinder during plantarflexion.
  12. 12. The ankle-foot prosthesis of claim 1, wherein piston displacement of the spring is different than piston displacement of the hydraulic cylinder.
  13. 13. The ankle-foot prosthesis of claim 1 , further comprising a dorsiflexion stop, wherein the dorsiflexion stop is engaged at a standing ankle position.
  14. 14. The ankle-foot prosthesis of claim 1, wherein the hydraulic cylinder comprises a first piston assembly, and wherein the spring is positioned inside the first piston assembly.
  15. 15. The ankle-foot prosthesis of claim 14, wherein the first piston assembly includes a first piston and first piston shaft, wherein the spring is positioned at least partly inside the first piston shaft.
  16. 16. The ankle-foot prosthesis of claim 2, wherein while the foot spring or foot spring assembly is subject to a ground reaction force and the ankle assembly rotates in a dorsiflexion direction, the spring is configured to release sufficient energy to equal or exceed energy loss from the dorsiflexion damping resistance.
  17. 17. The ankle-foot prosthesis of claim 16, wherein the prosthetic adapter, the hydraulic cylinder, and the base define a force triangle that defines an axis of rotation of the foot spring or foot spring assembly about the prosthetic adapter, wherein the spring creates a dorsiflexion biasing moment about the axis of rotation.
  18. 18. The ankle-foot prosthesis of claim 17, wherein the dorsiflexion biasing moment from the spring is always at least 3 Nm.
  19. 19. The ankle-foot prosthesis of claim 18, wherein the spring comprises a gas cavity containing one or more gases at a minimum pressure of 200-1000 psi.
  20. 20. The ankle-foot prosthesis of claim 19, wherein the dorsiflexion biasing moment from the spring at a standing position is 0.05-0.20 Nm/kg body weight.

Description

SYSTEMS AND METHODS FOR AN ARTICULATING PROSTHETIC JOINT TECHNICAL FIELD The present disclosure relates generally to prosthetic devices, and, more particularly, prosthetic devices such as but not limited to prosthetic ankles and other prosthetic joints. BACKGROUND Amputees are typically fitted with prosthetic devices that meet specific criteria for that particular amputee. For example, the size, shape, stiffness, and other properties of a prosthetic device are selected and tuned to match the size, shape, strength, and other physical properties and functionality of the given amputee. Changes in these properties of a given amputee may influence whether or not a particular prosthetic device will perform properly and according to expectations for the amputee. It is common for an amputee to change his/her prosthetic device when, for example, the amputee grows in height, weight, strength, or balance capability. Opportunities exist for providing prosthetic devices for amputees that account for changes in the amputee’s body and capabilities. There are available to amputees three general categories of prosthetic ankle-foot prosthesis designs which articulate during stance phase. One category is known as a single axis foot. This type of design has an ankle rotation axis and ankle rotation is resisted by elastomer bumpers. Elastomers exhibit creep over time, and therefore the ankle behavior is not consistent over time. The second category is hydraulic ankles. Hydraulic ankles, like single axis feet, are passive prosthetics. Hydraulic ankles suffer the drawback of energy dissipation during the gait cycle. In fact, energy loss is widely considered the largest design deficiency in hydraulic ankles on the market to date. The third category is powered ankles, such as the Ottobock® Empower. Unfortunately, powered ankles are very expensive, complex, and heavy. The various drawbacks to each of these categories create an ongoing need for new alternatives for prosthetic articulating ankles and other prosthetic joints. SUMMARY An aspect of the present disclosure involves prostheses and their components which provide articulation similar to the substituted biological joint without the energy losses associated with hydraulic-only joints. In the context of ankle-foot protheses, exemplary embodiments provide ankle articulation similar to a human ankle without the energy loss associated with hydraulic ankles. Energy is stored and then returned by one or more springs as the gait cycle progresses. In some embodiments, an exemplary spring for this purpose is an air spring. The air spring may be arranged to exert a force directly on the hydraulic fluid belonging to a dampening subsystem. Return of energy from the air spring may provide propulsion which is adjustable to the individual user. The propulsion effect is exhibited during the stance phase, in particular during dorsiflexion rotation that occurs during the stance phase. Even more particularly, the propulsion effect may be most notable during the mid-stance phase. Exemplary embodiments also permit adjustment of the hydraulic resistance. Accordingly, exemplary prostheses with such features are able to provide whatever resistance and/or propulsion a user desires using only passive (non-powered) components. Relatively high hydraulic resistance settings permit an exemplary prosthesis assembly to act much like a traditional hydraulic ankle. Utilizing relatively lower hydraulic resistance results in the ankle returning energy absorbed during heel strike and increasing the rate of tibial progression compared to a hydraulic-only ankle by creating a joint moment large enough to counteract a user’s applied body weight. According to an aspect of some embodiments, an articulating prosthetic foot is included which collects much of the heel impact energy (e.g., during initial contact and loading response subphases of the stance phase of the gait cycle) and returns it back to the user during tibial progression via a charged spring, e.g., a charged gas spring. Such configuration minimizes the otherwise significant energy loss associated with hydraulic-only fully mechanical articulating prosthetic feet. The spring may be charged by using hydraulic fluid (e.g., oil) displacement which occurs when the hydraulic piston is displaced in a closed hydraulic chamber. A further aspect of the present disclosure relates to an ankle assembly. The ankle assembly includes a base configured to be attached to a foot spring or foot spring assembly, an extendable link rotatably attached to the base and configured to control rotation of the ankle assembly, and a prosthetic adapter portion rotatably attached to the base and the extendable link and configured to be attached to a prosthetic worn by the user. The base, the extendable link, and the prosthetic adapter portion define a force triangle that defines an axis of rotation of the ankle assembly. The axis of rotation is positioned below and in line with the ce