FR3051661A1 - DEVICE FOR ANKLE PROSTHESIS CONTROLLED BY A MOTORIZED KNEE PROSTHESIS SENSITIVE TO THE PESANTOR - Google Patents

Abstract

An articulated ankle prosthesis controlled by a knee prosthesis sensitive to gravity. It allows a trans-femoral amputee patient the realization of different movements: walking, climbing a staircase, getting up from a chair. The rotation of the ankle is obtained in one direction by the pull of a spring, and in the other direction by the support of the subject on his heel, without the rotation of the ankle is moved by a motor. A braking device controlled by the prosthetic knee calculator keeps the ankle in its position outside the rotational movements. The invention, by allowing to maintain a ground support on the sole of the foot reduces the torque required for the motorization of the knee prosthesis and decreases the pressurization of the socket stump-prosthesis compared to the solutions of rigid dowels.

Description

The present invention relates to an articulated ankle prosthesis for transfemoral amputee, controlled by a motorized knee prosthesis (3) responsive to the acceleration of gravity (4). Its main characteristic is the exclusive use of the weight of the subject for rotation of the joint without recourse to the torque provided by an engine.

When combined with knee prostheses for trans-femoral amputees, ankle prostheses are not traditionally articulated. They are made by a fixed device, the prosthesis foot (8) being held perpendicularly to the tibia prosthesis (5) rigidly or slightly elastically. The absence of bending of the ankle during a search for support of the subject forwards to get up from a chair or to climb a stair step - has the first consequence, to move the contact on the ground and therefore the support of the subject, towards the tip of the foot, by increasing the distance to the center of gravity and the muscular mechanical torque of the femoral stump (1) - has the second consequence of increasing the necessary torque in the knee prosthesis ( 3), - and has the third consequence of subjecting the junction between the socket (2) and the stump (1) to a high torque that can cause the pressurization of the socket (2) which is normally maintained by atmospheric depression (13).

The rotation of the prosthesis foot according to the invention overcomes these disadvantages by restoring the natural fulcrum at the level of the sole of the foot. The approach of the point of support to the ground with the center of gravity of the subject has the first effect of reducing the muscular torque of the stump (1) and that of the knee prosthesis (3). By decreasing the angle of the stump with the vertical (4), it has the second effect to thwart the pressurization of the socket (2) by the reduction of the torsional torque, but also by the increase of the component of the weight of the subject under pressure in the socket (2). Other models of ankle prostheses are articulated and use the force of a motor for the rotational movement of the ankle, but they are more particularly intended for trans-tibial amputees. Rehashed by controlling the motor of the ankle to strain gauges measuring the ground pressure, they generate a torque, without using as the present invention, the resulting torque of the weight of the subject resting on the ground. In addition, given the large mass of their motor, in relation to the power required for the movement of an ankle, they can not be used for trans-femoral amputations because their mass disrupts excessively the operation of the knee prosthesis. the trans-femoral amputee by increasing the moment of inertia around the axis of rotation of the knee prosthesis. The invention overcomes this last drawback by removing the weight of the engine in a much lighter technical solution. Instead of creating a torque at the ankle with a motor, the invention exclusively controls the exercise of the torque resulting from the weight of the subject on his heel or on the front of the foot, by means of a braking device ( 10). The algorithm of the ankle calculator, using the reference verticality (4) and the angles of the stump and tibia transmitted by the knee prosthesis (3), identifies the position of the foot and releases the braking device when the couple of weight is in a direction favorable to the movement. Conversely, the joint is blocked by the brake when the torque is applied in a direction unfavorable to the movement.

By calling Cm the pair of the weight of the subject and Crot the necessary torque for movement, the algorithm performs the following function: if (Cm * Crot)> 0 the brake is released if (Cm * Crot) <0 the brake is set

The accompanying drawings illustrate the anchor device object of the invention.

Figure 1 shows the overall device.

The release of the braking device by the algorithm of the computer, authorizes the movement of the foot towards the upper stop (FIG. 2), when the body is resting on the front of the prosthesis foot, and towards the lower stop (FIG. 3), when the body joins the right station after the recovery phase.

FIG. 4 illustrates, in the case of the movement of getting up from a chair towards the standing station, the generation of a favorable torque and its exploitation by the algorithm of the device to release the braking.

In phase A, the weight of the subject, applied in its center of gravity G, induces a torque Cm which maintains the ankle on the upper stop.

In phase B, the weight of the subject, applied in its center of gravity G, induces a torque Cm favorable to the rotation of the ankle towards the right station. The algorithm releases the brake and simultaneously, the rotation of the ankle, under the effect of the torque of the weight, accompanies the elevation of the subject.

In phase C, the subject is in the right station, the joint has reached the lower stop and the brake is tightened again. During the entire movement, the stiffness of the femur (1) tibia (5) is ensured by the prosthesis knee motor (3)

The subject retains his equilibrium at all times since the resultant weight is always on the base of the foot support, and he controls the effort of rotation of the ankle by the intensity of the support on his heel. The favorable torque of the ankle is controlled by the natural sense of the subject's balance by means of the general position of the body (position of the arms, the shoulder line and the head). The invention therefore excludes the making of movements that require an autonomous force of impulse provided by the ankle, such as stroke or jump, but these two movements are not useful in the practical field of the invention, limited to elementary movements Usuals: walking, getting up from a chair to the right station, or climbing up and down stairs. These movements of the field of application all have the characteristic of offering mechanical couples exploitable by the algorithm for the rotation of the ankle. The invention comprises as a first feature a mechanical device for rotating two positions, high (7) and low (6), of the ankle, associated with a brake (10) controlled by a computer (3) identifying the absolute position of the foot by means of the vertical reference (4) provided by the knee prosthesis (3) via an electrical data link (12). The movement towards the high position (7) is obtained by means of a return spring (9) and that towards the low position by means of the support torque of the subject on the heel. The low position has the effect of resetting the spring tension. Whether it comes from the support torque or from the energy stored in the spring, the rotation results solely from the weight of the subject.

The release of the brake (10) controlled by the knee prosthesis (3) by means of the electrical signal, allows the passage from one position to another of the ankle. Each of the two positions is provided with a mechanical stop determining the position of the foot, which is maintained after rotation by the clamping of the brake (10). Thus, while standing the ankle is normally blocked by the brake.

In braked mode, if the subject voluntarily or involuntarily exerts a pressure on the tip of the foot which exceeds the normal braking torque, a movement is effected from one stop to the other by sliding of the brake contact parts (10). , bites or skates.

According to particular embodiments, the return spring and the braking device can be made by mechanical, pneumatic, hydraulic or electrical systems. The state in each of the two high and low positions is identified by the knee calculator by means of a position sensor.

When walking, when the foot is suspended on the back of the body, the release of the braking device by the algorithm of the computer (11), allows the movement of the foot to the high position under the effect of the recall spring (9) .When the foot is on the front of the body, following another set of de-tightening of the brake given by the computer (11), pressing on the heel causes the return to the low position (6) and the resetting of the spring (9). The device thus allows the foot to pass through the vertical position by avoiding the friction of the forefoot with the ground as it normally occurs without compensation of the pelvis with a rigid ankle prosthesis. When the foot is returned to the lower position (6), perpendicular to the tibia (5), the brake (10) is again tightened to solicit the support on the forefoot as it is necessary in a walk normal.

In a different movement of walking, for example to climb a stair step or to get up from a chair, the brake release instruction is given when the subject is looking for support on the front, allowing the ankle to bend on the high stop. The release instruction is again given to reach the right station on the low stop.

This mode of support provided by the ankle allows the subject to put his foot flat on the step, and avoids the inconvenience, as with a traditional rigid device, the support on the tip of the foot that creates a rear pair of tilting of the body, which must be compensated by a forward effort by means of a strong pull of the arms on the ramp of the staircase. At the level of the lower limbs, the angle of the femur with the vertical reduced, and the distance to the point of support ground shorter state, the torque required for movement is reduced both at the motor of the prosthesis and the residual femoral muscles.

The position of the top stop is characterized by an angle close to seventeen degrees per vertical port providing a 4 percent transfer of the weight of the subject in the socket stub connection to avoid pressurization of the link. .

The position of the bottom stop is characterized by an angle close to zero degrees from the vertical and set for a neutral equilibrium sensation of the subject standing, the verticality of the subject being measured by the computer.

The braking device is characterized in upright and upright position, by a holding torque without sliding of the braking edge allowing a difference of seven degrees forward with respect to the vertical in a normal search of equilibrium, and by a slip of rotation of the brake lobes beyond this value to the upper stop.

With reference to FIG. 1, the invention can be realized by means of articulated parts on a rotation shaft, equipped with a brake with bites or with a shoe (10) actuated by an electric power device controlled by the computer (11). ) from a reference of verticality data communicated by the prosthesis calculator via a data link (12).

A contactor or a photoelectric cell or a hall effect sensor communicates the information of one or the other of the two positions to the computer (11) in order to verify the correct execution of the rotation following the release of the brake (10).

The angular adjustment of the stops can be achieved by means of a set of removable metal wedges held by screws.

The ankle device according to the invention is particularly intended for elderly amputees or double amputees who can not be equipped with traditional prostheses.

Ankle device for trans-femoral amputee controlled by a knee prosthesis (3) characterized in that it comprises a two-position high and low rotation device, limited by stops (6X?)

Ankle device according to claim 1 characterized in that the braking device (10) comprises jaws configured to exert a holding torque without slipping rotation of the ankle for a deflection of the subject relative to the upright standing below seven degrees forward and for a rotation slip beyond this value.

Ankle device according to claim 1 characterized in that the rotation device comprises a spring (9) for returning the mechanism to the up position (7) and that the return to the lower position (6), which puts the spring in tension , is obtained without other means than the mechanical torque created by the support of the subject on his heel.

Ankle device according to Claim 1, characterized in that the rotation device comprises an upper stop (7) placed at an angle close to seventeen degrees with respect to the vertical allowing a transfer of four per cent of the weight of the subject into the stub (1) socket (2) counteracting the pressurization of this link (13), and by a low stop (6) placed at an angle close to zero to allow the right station in equilibrium.

Ankle device according to claims 3 and 4, characterized in that the rotation device comprises a sensor which identifies one or the other of the two positions of the rotation mechanism, said positions being transmitted by an electrical signal to the computer.

Claims (9)

1) Device for impregnated amputee femoral ankle controlled by a knee prosthesis (3) characterized in that it comprises a two-position rotation device, high and low, limited by stops (6) (7), and a braking device (10) which, when released by a computer (11) identifying the position of the foot (8) by means of the vertical reference (4) provided by the knee prosthesis (3), allows the rotation from one position to another under the sole effect of the weight of the subject without transmitting the force of an engine. 2) Ankle device according to claim 1 characterized in that the braking device (10) comprises jaws configured to exa-cer a holding torque without sliding of rotation of the ankle for a deviation of the subject from the vertical in standing up less than seven degrees forward and for a rotational slip beyond that value. 3) Anchor device according to claim 1 characterized in that the rotation device comprises a spring (9) for returning the mechanism to the upper position (7) and the return to the lower position (6), which puts the spring in tension, is obtained without other means than the mechanical torque created by the support of the subject on his heel. 4) A peg device according to claim 1 characterized in that the rotation device comprises a high stop (7) placed at an angle close to seventeen degrees with respect to the vertical permitting a transfer of four percent of the weight of the subject in the stub connection (1) socket (2) counteracting the pressurization of this connection (13), and by a low abutment (6) placed at an angle close to zero to allow the right station in equilibrium. 5) Anchor device according to claims 1 and 2, characterized in that the braking device (10) is actuated by an electrical device (11) which, at rest, maintains the rotation mechanism in one or the other of the two positions and which, when actuated releases the rotation of the ankle, under the effect of either the return spring (9) when the foot does not rest on the ground, or the support when the foot is in contact with the ground. 6) Anchor device according to claims 3 and 4, characterized in that the rotation device comprises a sensor which identifies one or other of the two positions of the rotation mechanism, said positions being transmitted by an electrical signal to the calculator . 7) Anchor device according to any one of the preceding claims characterized in that the action on the brake is transmitted by the computer (11) to the braking device by means of an electrical signal. 8) Ankle device according to any preceding claim characterized in that when walking, the computer (11) incorporating an algorithm is configured to release the brazing device and allow movement of the foot to the up position (7), when the foot is suspended on the back of the body, and to the lower position (6), when the foot is on the front of the body resting on the heel. 9) Ankle device according to any one of claims 1 to 7 characterized in that when elevated on a step or a chair, the calculator (11) incorporating an algorithm is configured to Ubérer the device braking and allow the movement of the foot to the upper stop (7), when the body is resting on the front of the prosthesis foot, and to the lower stop (6), when the body joins the right station.