NL1010209C2 - Artificial ankle prosthesis is attached to end of artificial lower leg and has automatic hydraulic cylinder system which enables prosthesis to mimic flexing action of real ankle and foot joints - Google Patents

Abstract

When the user 'rocks back on his heel', the switch (19) operates the valve (17) allowing the hydraulic piston to push the toe end away from the heel end. Later in the step, when the toe end touches the ground, the heel end operates the switch, shutting off the valve, and driving the heel and toe ends back towards each other.

Description

Ankle prosthesis

The invention relates to an ankle prosthesis. In a known ankle prosthesis, a lower leg part is pivotally connected to a foot part. A pivoting of the foot part relative to the lower leg part activates spring means placed between the two parts, for instance an elastic ring, whereby a resilient movement as well as a damping of the movement is obtained. Insofar as with the aid of this known ankle prosthesis, a part of the kinetic energy of the user is stored during the placement of the foot, this energy becomes available at a later stage.

A drawback of this known ankle prosthesis, however, is that the release of the stored energy takes place rather uncontrollably and a natural movement course is only obtained to a limited extent.

The object of the invention is to provide an ankle prosthesis, which is further optimized compared to the existing ankle prostheses and which provides a user with a virtually natural course of motion.

For this purpose the ankle prosthesis according to the invention is characterized by a lower leg part to be connected to the lower leg of a user, a heel part which can be pivoted relative to it substantially in a median plane, a toe part which can also be pivoted relative to the lower leg part in the same plane, a connecting the heel part to the toe part and spring-loaded to each other and a locking device for allowing or preventing a mutually directed rotation of the heel part and the toe part, respectively, such that such rotation is only permitted in a forward rotation position of the lower leg part relative to the heel part.

The median plane denotes a plane parallel to a plane that divides a user's body into a left and a right half.

In a starting position, the lower leg portion has said forward rotation position relative to the 1010209 2 heel portion. The locking arrangement hereby permits the rotation of the heel part and the toe part which are directed towards each other, which are therefore rotated towards each other under the influence of the spring means. This starting position, determined by stops, applies when the user makes a forward stepping movement with the leg provided with the ankle prosthesis and this leg is above the ground. When the respective leg is put down, this takes place with the heel part and is rotated relative to the lower leg part under the influence of the body weight. As a result, the lower leg part leaves the forward rotational position relative to the heel part, and rotation of the heel part and toe part can no longer take place. Rotating the heel part and the toe part away from each other, however, is readily possible and therefore takes place. The spring means is tensioned here.

During the unwinding of the foot, the rotated position of the heel part and the toe part is maintained until, at the end of the unwinding movement, when the foot only rests with the toe part on the bottom, the lower leg part with respect to the heel part again. has been rotated forward to the forward rotational position, in which the latch is actuated to again enable rotational rotation of the heel portion and the toe portion. Since, due to the forward rotation position of the lower leg part relative to the heel part determined by the stop, a rotation of the heel part relative to the lower leg part is not possible, a rotation of the toe part relative to the lower leg part takes place, and towards the heel part add, so that the outlet is supported during the walking movement. The force required to rotate the toe portion relative to the lower part during this phase of the walking movement is caused by the spring means which is tensioned during the laying down of the heel part.

Therefore, with the aid of the ankle prosthesis according to the invention, the force generated during the deposition of the foot is used to tension the spring means, and the energy stored thereby in the spring means can only be released when the unwinding movement of the foot is almost complete. has occurred and the lower leg portion has assumed the forward rotational position relative to the heel portion.

The released energy is then used to rotate the toe part, resulting in a sustaining push off force. With the aid of the ankle prosthesis according to the invention, the user experiences a natural course of movement, whereby a great ease of use is created and less effort is required for walking.

In this context, the possibility is mentioned that the moment at which the energy is released from the spring means can be set. The same is true with regard to the rate at which the energy is released. For this purpose, delay mechanisms and / or restrictions can be applied in, for example, pipes. This depends on and can lead to an improvement in walking behavior.

Within the general scope of the invention described above, there are various possibilities for a specific embodiment of various parts of the ankle prosthesis according to the invention. Thus, it is possible that the spring means is a gas spring. When the foot is put down with the heel and the heel part is pivoted relative to the toe part, this gas spring is compressed, and energy is stored. During the closing sales movement, the gas expands and the stored energy is released again.

In another preferred embodiment of the ankle prosthesis according to the invention it holds that the locking provision consists of a hydraulic cylinder connecting the heel part to the toe part, the cylinder chamber of which communicates via a fluid conduit with a buffer reservoir, wherein a control valve is included in the fluid conduit for regulating the fluid flow through the fluid conduit, depending on the rotational position between the lower leg part and the heel part.

When the control valve allows unobstructed fluid flow through the fluid conduit, the chopper can move back and forth relative to the toe part. However, the control valve can also take up such a position that only such a fluid flow through the fluid conduit is possible, which arises during the rotation of the chopping part 5 and the toe part. A rotation of the heel part and the toe part directed towards each other is prevented in such a situation.

In this context it is noted that the hydraulic cylinder concerned can also have two cylinder chambers located on either side of a piston, which are connected by the relevant fluid conduit. One of the two cylinder chambers then in fact forms the buffer reservoir.

Furthermore, it is advantageous in such a case if a switch operating the control valve is located between the heel part and the lower leg part. This switch is operated by the mutual rotation position between the heel part and the lower leg part. The switch can for instance be a hydraulic multi-way valve mounted on the lower leg part, which is actuated by the heel part and which is included in the fluid line. Without wishing to be exhaustive, an electrical switch can be mentioned as another example, which controls an electromagnetically operated valve in the fluid flow.

When, as explained above, the spring means is a gas spring and the locking device consists of a hydraulic cylinder connecting the heel part to the toe part, an extremely favorable embodiment of the ankle prosthesis is characterized by the fact that the heel part and the toe part are connected by a cylinder, the cylinder housing of which is divided by a piston into two cylinder chambers, one cylinder chamber of which is filled with a gas, and the other cylinder chamber of which is the cylinder chamber which communicates via the fluid line with a buffer reservoir, the piston is connected to the heel part or toe part, and the cylinder housing is connected to the toe part or heel part. In such an embodiment of the ankle prosthesis, the gas spring and the hydraulic cylinder are structurally advantageously combined into one part, which is not only structurally advantageous, but also yields considerable weight savings. An embodiment in which the piston of the cylinder in question is connected to the heel part and the cylinder housing to the toe part is hereby kinematic as an embodiment, wherein the piston is connected to the toe part and the cylinder housing to the heel part. .

As already briefly indicated in the foregoing, a control valve which is known per se can be used for the control valve. However, an extremely simple embodiment of the ankle prosthesis according to the invention is obtained when the control valve is an on and off switchable check valve. In the switched off position of the control valve, it does not function as a non-return valve, so that a fluid flow in both directions is possible. In the engaged position, however, the control valve functions as a non-return valve, so that a fluid flow is only possible in such a direction that rotation of the heel part and the toe part is possible.

According to another favorable embodiment of the ankle prosthesis according to the invention, when the preload of the spring means, for example a gas spring, is adjustable, the ankle prosthesis can be easily adapted to personal characteristics of the specific user, such as body weight. Adjustment of the bias of the spring means, such as a gas spring, takes place in ways already known per se to a person skilled in the art, so that no further explanation can be given here.

The walking comfort obtained with the ankle prosthesis according to the invention can be further improved if damping members are used for damping the rotation of the lower leg part relative to the heel part, respectively. the toe part. As a result, impact-like movements of the heel part resp. toe part in relation to the lower leg part are prevented.

1010209 6

Finally, a variant of the ankle prosthesis according to the invention is mentioned, wherein the lower leg part is also pivotable relative to the heel part and the toe part in a direction directed substantially perpendicularly to the said median plane. This ensures that good contact between the heel part and the heel part can be maintained at all times. toe part and the base are obtained, which further promotes a natural walking feeling for a user. This pivotability can also be damped by suitable means, while energy buffering and release can also take place here.

The invention is explained in more detail below with reference to the drawing, which shows an embodiment of the ankle prosthesis according to the invention.

Figure 1 shows schematically an embodiment of the ankle prosthesis according to the invention, and

Figures 2 to 5 show successive use positions of the ankle prosthesis shown in Figure 1 on a smaller scale.

The ankle prosthesis shown in Fig. 1 is attached to the lower leg of a user with the aid of a lower leg part 1, in a manner not shown in more detail. A heel part 2 is pivotally connected to the lower leg part 1 by means of a hinge 3. Similarly, a toe part 4 is connected to the lower leg part 1 via a hinge 5. Stops 6 and 7 determine the extreme positions of the heel part 2 and the toe part 4 relative to the lower leg part 1. Coatings are not shown to provide the prosthesis with a natural appearance.

The heel part 2 and the toe part 4 are connected to each other by means of a cylinder 8. The cylinder housing 9 is pivotally coupled to the chopping part 2 via a hinge 10, while the piston 11 and the piston rod 12 connecting thereto are connected to the toe part 4 via a hinge 13.

The piston 11 defines two cylinder chambers 14 and 15 within the cylinder housing 9. In the cylinder chamber 14 there is a hydraulic fluid, for instance oil. The cylinder chamber 14 communicates with a buffer reservoir 18 via a fluid conduit 16, in which a control valve 17 to be described hereinafter, is included. The other cylinder chamber 15 contains a gas, for example nitrogen. This cylinder chamber 15 is sealed with respect to the environment by means not further indicated.

The ankle prosthesis according to the invention furthermore comprises a switch 19 arranged on the lower leg part 1 and cooperating with the heel part 2, which connection is connected to the control valve 17 via a control line 20.

The possibility of movement of the heel part 2 relative to the lower leg part 1 (rotation about hinge 3) is schematically represented by arrow 21. The corresponding possibility of movement (rotation about hinge 5) is indicated with regard to the toe part 4 by arrow 22. Finally arrow 23 indicates the possibility of movement of the control valve 17, which will be explained in more detail later.

The position of the ankle prosthesis shown in Fig. 1 corresponds to a starting position or rest position. The heel part 2 and the toe part 4 are rotated as far as possible under the influence of the gas pressure in the cylinder chamber 15, the extreme position being determined by the stops 6 and 7. The switch 19 is activated by a stop 24 on the the chopping part 2. As a result of this activation, a signal is supplied via the control line 20 to the control valve 17, so that it is in the position shown in Fig. 1. Here, the fluid flow through the fluid conduit 16 is allowed in both directions (i.e. towards and away from the buffer reservoir 18).

The operation of the ankle prosthesis will now be explained in more detail with reference to Figures 2 to 5.

Fig. 2 shows the situation when the ankle prosthesis is placed on the ground with the heel part 2. Due to the force exerted (due to the weight of the user), the heel part 2 rotates about the hinge 3 relative to the lower leg part 1 in a median plane, ie a plane parallel to a plane 1010209 8 that the body of the user in left and right halves. As a result of the rotation of the chopping part 2, the distance between the hinges 10 and 13 increases, and since the toe part 4 is stopped by the stop 7, the piston 11 has to counter the gas pressure in the cylinder chamber 15. move to the right relative to the cylinder housing 9. The gas in the cylinder chamber 15 is compressed here.

Also, as a result of the rotation of the heel-10 part 2 relative to the lower leg part 1, the switch 19 has come out of engagement with the stop 24, as a result of which a signal is delivered via the control line 20 to the control valve 17, so that it moves to the position shown in fig. 2 is moved. In this position, the cylinder chamber 14 (or the fluid conduit 16 connecting thereto) is connected to the buffer reservoir 18 via a non-return valve 25, which allows only an oil flow from the buffer reservoir 18 to the cylinder chamber 14, and not vice versa. In this position of the control valve 17, the piston 11 can therefore move to the right, but not to the left. The energy stored in the compressed gas in the cylinder chamber 15 is therefore maintained until the control valve 17 returns to its position shown in Fig. 1 at a later time.

During the next phase of walking, the ankle prosthesis tilts forward about the point of contact between heel part 2 and the ground, so that the toe part 4 also rests on the ground. This situation is shown in Fig. 3. Depending on the applied load, the piston 11 in the cylinder housing 9 can move even further to the right. However, this is not necessary. However, a movement of the piston 11 to the left is not possible, as explained above.

In Fig. 4 a next phase is shown; the user has moved his body weight further forward, so that the lower leg part 1 is tilted forward. The full body weight now rests on the toe part 4, while the heel part 2 is released from the bottom. The lower leg part 1 pivots so far forward, until the stop 6 engages the heel part 2 and the switch 19 also comes into contact with the stop 24. This activates the control valve and repositions it in the position shown in Fig. 1. Now, under the influence of the gas pressure prevailing in the cylinder chamber 15, the piston 11, as seen in Fig. 4, can be moved to the left, oil being displaced from the cylinder chamber 14 and reaching the buffer reservoir 18 via the fluid line 16 and the control valve 17. .

Due to the displacement of the piston 11 relative to the cylinder housing 9 to the left, since the heel part 2 already rests against the stop 6, the toe part 4 is pulled towards the lower leg part 1. Hereby a pushing force is exerted on the ground by means of the toe part 4, which supports the user in the walking movement. This finally achieves the position of the ankle prosthesis shown in Fig. 5.

The foot is then lifted, again taking the starting position shown in Fig. 1. After this, the described process repeats itself with the respective leg during each step.

The gas-filled cylinder chamber 15 functions as an energy buffer. Of course, a mechanical spring means could also be used, such as a compression spring. The cylinder chamber 14 filled with oil 25, in combination with the control valve 17, functions as a locking device to temporarily block the movement of the piston 11 in one direction. Instead of such a locking device, mechanical locking devices can also be used, which are activated and deactivated under the influence of the relative position between the heel part 2 and the lower leg part 1. After all, the release of the stored energy only has to take place when a mutual position of the heel part 2, toe part 4 and lower leg part 1 corresponding substantially to fig. 4 is reached.

This is a position in which the lower leg part 1 has a forward rotational position relative to the heel part 2.

1010209 10

Not shown are damping members, if used, at the location of the hinges 3 and 5. These can prevent the rotation of the lower leg part 1 relative to the heel part 2, respectively. mute toe section 4. It is also possible that the lower leg part 1 can perform a limited rotational movement with respect to the heel part and the toe part in a direction substantially perpendicular to the said median plane. This ensures that at all times an engagement distributed over a large area between the chopping part or.

10 toe part and the substrate takes place.

By using a pneumatic spring in the form of a cylinder chamber 15 which is filled with gas, a pre-tension can be adjusted in a simple manner by choosing an appropriate initial pressure. In addition, a suitable initial volume and a suitable surface of the piston 11 can be selected, in order to adjust the spring characteristic of the gas spring obtained thereby as required.

The invention is not limited to the embodiment described above, which can be varied in many ways within the scope of the invention defined by the claims.

1010209

Claims (9)

Ankle prosthesis, characterized by a lower leg part to be connected to the lower leg of a user, a heel part which can be pivoted relative to it substantially in a median plane, a toe part which can also be pivoted in the same plane with respect to the lower leg part, spring part connecting to and against the toe part and loading spring loaded against each other and a locking provision for permitting or preventing a mutually directed rotation of the heel part and the toe part, respectively, such that such a rotation is only permitted in a forward rotation position of the lower leg part relative to the heel part. Ankle prosthesis according to claim 1, characterized in that the spring means is a gas spring. Ankle prosthesis according to claim 1 or 2, characterized in that the locking provision consists of a hydraulic cylinder connecting the heel part to the toe part, the cylinder chamber of which communicates via a fluid line with a buffer reservoir, wherein a control valve in the fluid line is included for controlling the flow of fluid through the fluid conduit, depending on the rotational position between the lower leg portion and the heel portion. Ankle prosthesis according to claim 3, characterized in that a switch operating the control valve is located between the heel part and the lower leg part. Ankle prosthesis according to claim 3 or 4 and claim 2, characterized in that the heel part and the toe part are connected by a cylinder, the cylinder housing of which is divided by a piston into two cylinder chambers, the one cylinder chamber of which is filled with a gas, the other cylinder chamber of which is the cylinder chamber which communicates via the fluid conduit with a buffer reservoir, the piston being connected to the chopping part or toe part, and the cylinder housing to the toe part or chopping part. 1010209 Ankle prosthesis according to any one of claims 3-5, characterized in that the control valve is a check valve that can be switched on and off. Ankle prosthesis according to any one of the preceding claims, characterized in that the preload of the spring means is adjustable. Ankle prosthesis according to any one of the preceding claims, characterized in that damping members are used for damping the rotation of the lower leg part relative to the heel part or the toe part, respectively. Ankle prosthesis according to any one of the preceding claims, characterized in that the lower leg part is also pivotable relative to the heel part and the toe part in a direction substantially perpendicular to said median plane. 1010209