US-20260124048-A1 - METHOD FOR CONTROLLING A TRANSTIBIAL PROSTHESIS AND TRANSTIBIAL PROSTHESIS

US20260124048A1US 20260124048 A1US20260124048 A1US 20260124048A1US-20260124048-A1

Abstract

Inventors

Andreas Bohland
Alexander Pappe
Martin Seyr

Assignees

OTTO BOCK HEALTHCARE PRODUCTS GMBH

Dates

Publication Date: 20260507
Application Date: 20231005
Priority Date: 20221010

Claims (9)

1 . A method for controlling a lower leg prosthesis comprising a foot element, a lower leg element pivotably arranged thereon and an adjustable resistance device for applying a resistance against a swivelling of the foot element relative to the lower leg element, wherein a first switching angle is defined as a predetermined ankle angle value between the lower leg element and the foot element, a second switching angle is defined as a predetermined lower leg angle value of the absolute angle of the lower leg, the method comprising the steps: determining, at least also on the basis of a height difference between the position of the foot element in a step cycle and the position of the foot element in the previous step cycle, whether the wearer of the lower leg prosthesis is walking downhill, and increasing the resistance of the resistance device to a predetermined resistance value when a block criterion is met, wherein the block criterion is met if it has been determined that the wearer is not walking downhill and the second switching angle is reached, or if it has been determined that the wearer is walking downhill and the switching angle reached later in the step cycle is reached.
2 . The method according to claim 1 , characterized in that the predetermined resistance value is big enough to prevent a further swivelling of the foot element relative to the lower leg element.
3 . The method according to claim 1 , characterized in that the height difference between the position of the foot element in the stance phase of the two step cycles is determined.
4 . The method according to claim 1 , characterized in that a pitch angle, which is determined from the height difference and a length difference between the positions of the foot element, is used to determine whether the wearer of the lower leg prosthesis is walking downhill.
5 . The method according to claim 4 , characterized in that the wearer is deemed to be walking downhill if the pitch angle is smaller than a limit angle, which is preferably between 0° and −10° and particularly preferably is −3°.
6 . The method according to claim 1 , characterized in that the predetermined ankle angle value is between 80° and 100°, preferably 90°.
7 . The method according to claim 1 , characterized in that the predetermined lower leg angle value is between 80° and 100°, preferably 90°.
8 . A lower leg prosthesis with a foot element, a lower leg element pivotably arranged thereon and an adjustable resistance device for applying a resistance against a swivelling of the foot element relative to the lower leg element, wherein the lower leg prosthesis comprises at least one sensor for determining a height difference, at least one sensor for determining an ankle angle, at least one sensor for determining the absolute angle of the lower leg, and an electrical control unit that is configured to conduct a method according to one claim 1 .
9 . The lower leg prosthesis according to claim 8 , characterized in that the at least one sensor for determining the ankle angle comprises an absolute angle sensor for determining the absolute angle of the lower leg element and an absolute angle sensor for determining the absolute angle of the foot element.

Description

The invention relates to a method for controlling a lower leg prosthesis comprising a foot element, a lower leg element pivotably arranged thereon and an adjustable resistance device for applying a resistance against a swivelling of the foot element relative to the lower leg element. The invention also relates to a lower leg prosthesis that can be controlled using such a method. Lower leg prostheses of the type described above can generate different resistances against a swivelling of the foot element relative to the lower leg element during a step cycle via the adjustable resistance device. This has been used in the prior art for many years to imitate the natural gait. Generally, it is important that the resistance is significantly increased approximately in the middle of the stance phase of a step cycle. This often goes so far that further swivelling of the foot element relative to the lower leg element is no longer possible from this point onwards. The stance phase of a step cycle is defined by the foot element being in contact with the ground. From the moment the resistance is increased, a further swivelling of the foot element relative to the lower leg element is not possible or only possible with difficulty. The foot then rolls over the forefoot, which is essentially formed by the toes. This changes the lever length over which rolling takes place. From the prior art, it is known to make the point at which the resistance is increased dependent on the gradient of the surface. For example, if the wearer walks up a ramp, the switching point at which resistance is increased should be postponed, i.e. shifted to a later point in time, within the step cycle. In the process, a foot element and/or a lower leg element is often used that is equipped with an absolute angle sensor with which the inclination of the foot element during the stance phase of the step cycle can be determined. This renders it easy to identify, for example, whether the wearer is walking up or down a slanted plane, such as a ramp. However, this method cannot be applied if, for example, it is to be determined whether the wearer of the lower leg prosthesis is walking up or down stairs. The angle of inclination of the foot element is the same regardless of the movement of direction as the step is horizontal. In addition, the method described reaches its limits when the terrain on which the wearer of the lower leg prosthesis is moving does not form an even surface. If the surface is uneven, the inclination of the foot element cannot or at least cannot always be used to reliably determine the gradient of the surface and when the switching point should occur. As such, it is known from DE 10 2012 125 256 A1 to define two switching angles. The first switching angle is defined as a predetermined ankle angle value between the lower leg element and the foot element. Therefore, as soon as the ankle angle that is detected to control the lower leg prosthesis reaches said predetermined ankle angle value, the first switching angle is deemed to have been reached. The second switching angle is defined as a predetermined lower leg angle value of the absolute angle of the lower leg. Regardless of the value of the ankle angle between the lower leg element and the foot element, the second switching angle is deemed reached when the absolute angle of the lower leg reaches the predetermined lower leg angle value. In order to now control the lower leg prosthesis, it must be determined which of the two defined switching angles is to be the angle at which the resistance of the resistance device should be increased. The prior art suggests always using the switching angle that occurs first within the respective step cycle, regardless of a detected position of the foot element in the stance phase. This is a good choice in many situations, but in some situations it does lead to problems. For example, the switching angle may be defined as a right angle, i.e. a 90° angle. This means that there is a right angle between the lower leg element and the foot element, for example the contact surface that comes into contact with the ground, when the first switching angle is defined. The second switching angle may also be defined as a 90° angle. This means that the second angle is reached when the lower leg element is perpendicular, i.e. extends parallel to the acting force of gravity. These definitions of the two switching angles mean that the second switching angle is reached first when walking downwards along a ramp. Consequently, the resistance is increased when the lower leg element is vertical, which leads to a more stable stance, but results in an unnatural gait. However, this definition of the two switching angles means that the first switching angle is reached first when walking up the ramp. This, however, is too early when walking upwards and leads to a premature increase in the resistance applied by the resistance device. The invention thus aims to further develop a metho