NL2026074B1

NL2026074B1 - A knee-ankle prosthesis

Info

Publication number: NL2026074B1
Application number: NL2026074A
Authority: NL
Inventors: Vallery Heike; Gijs Van Der Helm Simon; Smit Gerhardus
Original assignee: Univ Delft Tech
Priority date: 2020-07-16
Filing date: 2020-07-16
Publication date: 2022-03-21

Abstract

prosthesis (20) comprising an artificial knee joint (30), lower leg (40), ankle joint (50), and foot (60), and provided with a first prosthesis portion (70) to con— trol bending of the knee joint (30), and a second prosthesis portion (80) to control bending of the ankle joint (50), wherein the first prosthesis portion (70) comprises a hydraulic or pneu— matic knee actuator (l) and the second prosthesis portion (80) comprises a hydraulic or pneumatic ankle actuator (2), and that the knee actuator (l) and the ankle actuator (2) connect to and share a single hydraulic or pneumatic pressure accumulator (3) or tank.

Description

A knee-ankle prosthesis The invention relates to a knee-ankle prosthesis com- prising an artificial knee joint, lower leg, ankle joint, and foot, and provided with a first prosthesis portion to control bending of the knee joint, and a second prosthesis portion to control bending of the ankle joint.

U52015/0182354 discloses a femoral knee-ankle prosthe- sis intended for persons who are lower-limb amputees but still have a segment suitable for a femoral connection and a tibial connection connected to the femoral segment based on an artic- ulation which reproduces the movements of the knee, the said tibial segment being articulated on one foot based on an ar- ticulation reproducing the movements of the ankle. The pros- thesis has a first damper, the ends of which are joined re- spectively with the femoral and tibial segments, and another hydraulic damper of which the ends are joined respectively with the tibial and foot segment. The chamber of the first hydraulic damper is connected to the chamber of the second hy- draulic damper and the prosthesis further has means of con- trolling the first and/or second hydraulic damper depending on the phase of the walking cycle such as the stance phase or the swing phase and/or real-life situations such as stairs, slopes or standing in such a manner that the flexion of the knee al- lows the dorsiflexion of the ankle in proportion to the move- ment of the knee during the stance phase and such that the flexion of the knee results in the dorsiflexion of the ankle during the swing phase.

It is an object of the invention to provide a light prosthesis at low cost.

It is a further object of the invention to provide a passive solution for the control of the knee joint and ankle Joint.

The prosthesis of the invention is characterized by the features of one or more of the appended claims.

First and foremost the prosthesis of the invention is characterized in that the first prosthesis portion is a hy- draulic or pneumatic knee actuator and the second prosthesis portion is a hydraulic or pneumatic ankle actuator, and that 40 the knee actuator and the ankle actuator connect to and share a single hydraulic or pneumatic pressure accumulator or tank. This arranges that when going from a standing up position to a sitting down position energy can be stored, and that energy can be used as a support when standing up from a sitting down position. In this manner the load applied to the healthy limb of the user of the prosthesis will be limited. Furthermore the construction of the prosthesis of the invention obviates the requirement for additional external energy to support the standing up movement.

It is desirable that the knee actuator connects to the pressure accumulator or tank via a (solenoid or proportional) valve or valves. By controlling the (sclenoid or proportional) valve or valves, pressure from the pressure accumulator or tank can release and provide the supportive function when the user is moving from the sitting down position to the standing up position.

Preferably the knee actuator connects to the pressure accumulator or tank via a check valve or valves. The energy that can be regained when moving from the standing up position to the sitting down position and which comes available at the knee actuator, can thus be stored and maintained in the pres- sure accumulator or tank, because the check valve or valves prevents the pressure from escaping. Accordingly this prevents unwanted knee extension when the user of the prosthesis of the invention is sitting down.

The stroke and diameter of the ankle and knee actua- tors can be suitably optimized to match the natural relation between angle and torque as closely as possible. A nonlinear relation exists between the ankle angle and the required ankle torque. Thus it has been found preferable that the ankle actu- ator has a smaller stroke volume than the knee actuator, which restricts the influence of the ankle actuator on the pressure inside the system.

When a full motion from sitting down to standing up is executed, the required support can be accomplished by pressur- izing an opposite chamber of the ankle or knee actuator. In another arrangement with more components the second prosthesis portion further comprises an auxiliary ankle actuator system which comprises in combination a second ankle actuator linked 40 to a separate pressure tank. The main ankle actuator and the auxiliary ankle actuator counteracting each other ensures an equilibrium point of the ankle close to the sitting down posi- tion. It is remarked that it is also possible that the second prosthesis portion comprises a spring instead of the just- mentioned auxiliary ankle actuator system.

The invention will hereinafter be further elucidated with reference to the drawing of an exemplary embodiment of a knee-ankle prosthesis according to the invention that is not limiting as to the appended claims.

In the drawing: ~figure 1 shows the knee and ankle torque during a sit-to-stand transition, as published in ref. [2]; “figure 2 shows schematically selected features of the prosthesis of the invention; and ~figure 3 shows a pneumatic system intended to form part of the prosthesis of figure 2.

Whenever in the figures the same reference numerals are applied, these numerals refer to the same parts. A sit-to-stand transition consists of three phases: trunk flexion, momentum transfer and extension, see ref. [1]. Fig. 1 shows the joint torque of knee and ankle during the transition. In the trunk flexion phase the trunk flexes and the ankle dorsiflexes. In the momentum transfer phase, the an- kle dorsiflexes further. To accommodate ankle dorsiflexion, the ankle plantarflexion torque is low during the first two phases of the transition. In the extension phase the knee ex- tends and the ankle plantarflexes. A high torque is required at the knee and ankle to accommodate this.

It is an object of this invention to support transfem- oral amputees during the sit-to-stand and stand-to-sit transi- tions. The energy required for the support is stored during the stand-to-sit transition and released during the sit-to- stand transition. To achieve one thing and another a knee- ankle prosthesis is proposed as will be further elucidated hereinafter with reference to figures 2 and 3 in combination. A schematic drawing of the prosthesis of the invention without details is shown in Fig. 2. In Fig. 3 the pneumatic system of the prosthesis of figure 2 is shown.

The knee-ankle prosthesis 20 of the invention compris- 40 es an artificial knee joint 30, lower leg 40, ankle joint 50,

and foot 60, which is provided with a first prosthesis portion 70 to control bending of the knee joint 30, and a second pros- thesis portion 80 to control bending of the ankle joint 50, wherein the first prosthesis portion 70 comprises a hydraulic or pneumatic knee actuator 1 and the second prosthesis portion 80 comprises a hydraulic or pneumatic ankle actuator 2. The knee actuator 1 and the ankle actuator 2 connect to and share a single hydraulic or pneumatic pressure accumulator 3 or tank.

For energy storage and release, preferably pneumatic actuators are selected, because of their high energy density. The energy is stored in said pressure accumulator 3 or tank in the form of pressurized air or a compressible liquid.

A main pneumatic circuit of the knee-ankle prosthesis comprises two actuation cylinders 1, 2, a pressure tank 3, two check valves 5, 6 and a (solenoid or proportional) valve

4. During a stand-to-sit transition an air volume in the knee actuating cylinder 1 will decrease, which will increase the pressure through the check valve 5 in the pneumatic system, 20 particularly in the pressure accumulator 3 or tank. When the stand-to-sit transition is completed, the air cannot flow out of the pressure accumulator 3 or tank back to the knee actuat- ing cylinder 1, which prevents unwanted knee extension while the user is seated.

Opening the (solenoid or proportional) valve 4 allows the air to flow back from the pressure tank 3 to the knee ac- tuating cylinder 1, to provide an extension torque in the knee during a sit-to-stand transition. The ankle actuating cylinder 2 is connected directly to the pressure accumulator 3 or tank.

Preferably the ankle actuating cylinder 2 has a smaller diame- ter and a smaller stroke than the knee actuating cylinder 1, so as to arrange that the movement of this ankle actuating cylinder 2 has a limited influence on the pressure in the main pneumatic circuit.

As the ankle torque graph in Fig. lb shows, the ankle torque has a non-linear relationship with the ankle angle, passing through the same angle twice with a different torque. To make this possible, the ankle actuating cylinder 2 has to remain connected to the knee actuating cylinder 1. However 40 this poses a problem as high ankle torque values do not occur simultaneous with high knee torque values. Since the knee and ankle actuating cylinders 1, 2 share the connection with the pressure accumulator 3 or tank, the pressure is the same in both knee- and ankle actuating cylinders 1, 2. Consequently 5 high actuator forces, and thus high joint torques, will occur simultaneous in the prosthesis, if no further measures would be taken. In connection therewith the second prosthesis por- tion 80 further comprises an auxiliary ankle actuator system 90 which comprises in combination a second ankle actuator 9 linked to a separate pressure tank 10.

The ankle actuating cylinder 2 is not disconnected from the pressure accumulator 3 or tank while seated, because the sec- ond (auxiliary) ankle actuating cylinder 9 ensures an equilib- rium point that is close to the seated ankle position.

As just explained the second (auxiliary) ankle actuat- ing cylinder 9 is added to counter the effect of the simulta- neous occurrence of high actuator forces and high joint tor- ques. The second (auxiliary) ankle actuating cylinder 2 is connected directly to a separate pressure tank 10. The second (auxiliary) ankle actuating cylinder 9 supplies a high ankle plantarflexion torque at the end of the cycle. The primary an- kle actuating cylinder 2 supplies a dorsiflexion torque to counter the plantarflexion torque at the start of the transi- tion. It is remarked that the second (auxiliary) ankle actuat- ing cylinder 9 may in some embodiments be dispensed with, par- ticularly when a chamber of the primary ankle actuating cylin- der 2 opposite to the piston of the ankle actuating cylinder 2 is pressurized.

The pre-pressure in both pressure accumulators or tanks 3 and 10, as well as the volume of the pressure tank 3 in the main pneumatic circuit can be adjusted to account for the body weight and the torque that is required for the user. The pre-pressure in both circuits is set by supplying pres- sured air to inlet check valves 6 and 11 connected to the pressure tanks 3 and 10.

Although the invention has been discussed in the fore- going with reference to an exemplary embodiment of the pros- thesis of the invention, the invention is not restricted to this particular embodiment which can be varied in many ways 40 without departing from the invention. The discussed exemplary embodiment shall therefore not be used to construe the append- ed claims strictly in accordance therewith. On the contrary the embodiment is merely intended to explain the wording of the appended claims without intent to limit the claims to this exemplary embodiment. The scope of protection of the invention shall therefore be construed in accordance with the appended claims only, wherein a possible ambiguity in the wording of the claims shall be resolved using this exemplary embodiment.

REFERENCES

[1] M. Schenkman, R. A. Berger, P. 0. Riley, R. W. Mann, and W. A. Hodge, “Whole Body Movements During Rising to Standing from Sitting,” Physical Therapy, vol. 70, no. 10, pp. 638-651,

1990.

[2] C. A. M. Doorenbosch, J. Harlaar, M. E. Roebroeck, and G.

J. Lankhorst, “Two Strategies of Transferring from Sit-To- Stand; The Activation of Monoarticular and Biarticular Mus- cles,” Journal of Biomechanics, vol. 27, no. 11, pp. 1299- 1307, 1994.

Aspects of the invention are itemized in the following section.

1. A knee-ankle prosthesis (20) comprising an artifi- cial knee joint (30), lower leg (40), ankle joint (50), and foot (60), and provided with a first prosthesis portion (70) to control bending of the knee joint (30), and a second pros- thesis portion (80) to control bending of the ankle joint (50), characterized in that the first prosthesis portion (70) comprises a hydraulic or pneumatic knee actuator (1) and the second prosthesis portion (80) comprises a hydraulic or pneu- matic ankle actuator (2), and that the knee actuator (1) and the ankle actuator (2) connect to and share a single hydraulic or pneumatic pressure accumulator (3) or tank.

2. The knee-ankle prosthesis according to claim 1, characterized in that the knee actuator (1) connects to the pressure accumulator (3) or tank via a valve (4) or valves.

3. The knee-ankle prosthesis according to claim 1 or 2, characterized in that the knee actuator (1) connects to the pressure accumulator (3) or tank via a check valve (5) or valves.

4, The knee-ankle prosthesis according to any one of 40 claims 1 — 3, characterized in that the ankle actuator (2) has a smaller stroke volume than the knee actuator (1).

5. The knee-ankle prosthesis according to any one of claims 1 — 4, characterized in that the ankle actuator (2) connects to the single pressure accumulator (3) or tank with- out restriction, such as a valve.

6. The knee-ankle prosthesis according to any one of claims 1 - 5, characterized in that the second prosthesis por- tion (80) further comprises an auxiliary ankle actuator system (90) which comprises in combination a second ankle actuator (9) linked to a separate pressure tank (10).

7. The knee-ankle prosthesis according to any one of claims 1 - 5, characterized in that the second prosthesis por- tion (80) further comprises a spring.

Claims

CONCLUSIONS

A knee-ankle prosthesis (20) comprising an artificial knee joint (30), lower leg (40), ankle joint (50) and foot (60), and having a first prosthetic member (70) to control flexion of the knee joint (30) and a second prosthesis part (80) for controlling the bending of the ankle joint (50), characterized in that the first prosthesis part (70) comprises a hydraulic or pneumatic knee actuator (1) and the second prosthesis part (80) comprises a hydraulic or pneumatic single actuator (2), and that the knee actuator (1) and the single actuator (2) are connected to and share a single hydraulic or pneumatic pressure accumulator (3) or tank.

Knee-ankle prosthesis according to Claim 1, characterized in that the knee actuator (1) is connected to the pressure accumulator (3) or tank via a valve (4) or valves.

Knee-ankle prosthesis according to Claim 1 or 2, characterized in that the knee actuator (1) is connected to the pressure accumulator (3) or tank via a non-return valve (5) or valves.

Knee-ankle prosthesis according to one of Claims 1 to 3, characterized in that the ankle actuator (2) has a smaller stroke volume than the knee actuator (1).

Knee-ankle prosthesis according to one of Claims 1 to 4, characterized in that the ankle actuator (2) is connected to the single pressure accumulator (3) or tank without flow restriction, such as a valve.

A knee-ankle prosthesis according to any one of claims 1 to 5, characterized in that the second prosthesis part (80) further comprises an additional ankle actuator system (90) which in combination comprises a second ankle actuator (9) coupled to a separate pressure tank (10). includes.

A knee-ankle prosthesis according to any one of claims 1 to 5, characterized in that the second prosthesis part (80) further comprises a spring.