DE10237373A1 - Artificial joint - Google Patents

Abstract

The invention relates to an artificial joint (1), in particular an artificial hand, consisting of several articulated links (2, 3). The individual links (2, 3) are connected to one another by means of an elastic connecting element (4) so as to be pivotable about several axes, so that in each case a tensile force introduced by means of a traction means (8, 9) for bending and stretching the respective link (2, 3) is provided. In order to be able to implement both a high load capacity for the transmission of large forces and a large number of degrees of freedom for different gripping functions regardless of the respective joint position, the joint gap (7) between the adjacent joint surfaces (5, 6) is used by means of the traction means (8, 9) if necessary reduced in such a way that the desired number of degrees of freedom can be set and at the same time a stiffening of the joint (1) can be achieved.

Description

The invention relates to an artificial Joint, especially an artificial one Hand, consisting of several articulated links, where in each case at least one movable by means of an actuator Traction means for bending and stretching the limb is provided.

Such an artificial joint is, for example, by DE-AS 22 45 503 known. It already describes the use of tension bands, which are fixed at the ends of the limb tips, an actuating device for bending and a further actuating device for stretching and thus for resetting the link against the bending movement being provided in each case. In addition, this hand has an angled drawstring through which the thumb can be brought to a base support in different angular positions. A special arrangement is intended to ensure that the thumb can be moved in three swivel positions, so that the tip of the thumb can be brought into contact with every single finger or fingertip and very different gripping positions can be achieved.

Also shows the US 50 80 682 already an artificial hand that can be used as a prosthesis. The traction devices intended for bending and stretching the links are fixed at the tips of the outer links and are tightened by guides.

The EP 01 58 659 also discloses the use of elastic materials in an artificial hand, wherein additional guides of the traction means are connected to spring elements.

Through the DE-OS-15 66 311 an artificial hand for prostheses with bioelectric control is also known, which can also be used for manipulators and has elastic transmission rods. The actuators assigned to the respective links are controlled by a performance potential tapped from the cut muscle.

More artificial joints are through the US 25 53 827 . US 42 46 661 . US 46 23 354 . US 49 55 918 and the DE-OS 21 43 850 known.

All known joints have however, the common disadvantage that they have the two main objectives, on the one hand with regard to the desired Mobility with a variety of degrees of freedom in healthy limbs the dexterity ensures and the one you want high resilience for transmission greater forces only in very limited Measurements with each other can reconcile. Those known for natural limbs So far, however, properties have not been achieved by artificial joints. The restrictions that of the carrier of such a prosthesis are therefore considerable and limit thereby the executions manual activity clearly one.

Object of the present invention it is therefore an artificial one Execute joint of the type mentioned in such a way that both a high Resilience for transmission greater Forces than also a variety of degrees of freedom for different gripping functions is feasible.

This object is achieved with a artificial Joint according to the characteristics of claim 1 solved. The subclaims concern particularly useful further training the invention.

According to the invention is therefore an artificial joint provided in which the individual links by an elastic Connecting element are connected to each other in such a way that a joint gap between the limbs by introducing a tensile force in at least one of the traction means of the link can be reduced. This will the respective degrees of freedom, which the mobility of the limbs determine, not unchangeable specified, but are determined by the introduction of the tractive force. This allows with a small, for example largely weak bend of the link introduced a large number of degrees of freedom by means of of the connecting element can be realized, which is not only serves the realization of a multi-joint, but through its elastic properties also a torsion about the longitudinal axis of the Limbs and a viscoelastic stretching of the joint (extension) in the direction of, for example, the fingertip. As soon as comparatively large tensile forces, for example, for holding heavy loads at the same time the joint gap and thereby the number of degrees of freedom are reduced, which stiffens the joint. This allows you to limited Agility great Loads are held. The properties of the artificial that can be achieved in this way Joint, which is primarily intended for prostheses, however in principle also for technical applications is suitable, therefore unite in previously unknown Dimensions both a high level of Mobility through a variety of degrees of freedom, as well high resilience depending from the tensile forces introduced.

An embodiment of the present invention proves to be particularly promising in which the joint gap can be fixed independently of a bent or extended position of the link. The movement into the flexed or the extended position is basically initiated in that the tensile forces assigned to the movement differ from one another. A desired position of the link can therefore be set by both large and low tensile forces, provided that they are in equilibrium. By adjusting this level of equilibrium, therefore, the position of the limb does not, but it does the joint gap and thus the stiffness and the number of degrees of freedom, regardless of the joint position and the relative position of the links to each other, changed.

Basically, the gap width of the joint gap determines the number of degrees of freedom. Especially Cheap it is, however, also when the joint with decreasing gap width the joint gap also a reduced number of degrees of freedom having. This leads a reduced gap width, the initiation of an increased tensile force is achieved, at the same time a gradual reduction in the number degrees of freedom and an increase in rigidity.

As particularly promising also shows a modification of the invention, in which the Joint gap reduced to zero when a predetermined tensile force is reached is, with adjacent articular surfaces the limbs flat lie against each other. When a predetermined tensile force is reached deleted hence the joint gap, so that the adjacent convex and concave Articular surfaces against each other lie and thereby the power transmission takes place directly from one link to the adjacent link without that the joint is strained. The articular surfaces can do this also form-fitting lie against each other to create a defined, stable joint position to be specified when initiating the maximum pulling force.

It turns out in practice as particularly useful if the connecting element made of a viscoelastic material, in particular Silicone. This is due to the rheological properties additionally a resilience and toughness to the elastic properties achieved by the sudden force in particular muted and therefore cannot damage the joint. simultaneously the tensile mechanical behavior of the joint under stress improved. It is particularly advantageous if the traction means Nylon are made. This can high tractive forces are transmitted with a low susceptibility to wear. Also points Nylon optimal sliding properties so that those of the actuator actuating forces to be applied comparatively are low. Steel wire is another suitable means of traction and natural String material possible.

The traction means could be shortened by means of a Spindle can be wound up or a hydraulic or pneumatic Have drive. On the other hand, an embodiment is particularly promising of the present invention, in which the actuator acts as a linear actuator is executed. As a result, the space requirement is comparatively small and at the same time positioning is achieved through an exactly reproducible positioning movement improved. The actuator can thereby also inside the artificial Articulated prosthesis can be accommodated, which increases comfort can be significantly improved.

Another particularly practical one Embodiment of the invention is achieved when the joint the basic structure supporting the limbs which has several unaffected by the movement of the limbs and has base elements which can be placed against one another by the traction means. This can increase the gain of the joint not only in the individual limbs of the joint, but can also be used in the basic elements of the basic carrier, which thereby in the unloaded state a high degree of flexibility and at Initiation of the tensile force has a high degree of rigidity.

Another particularly useful embodiment The present invention is also achieved in that the Limbs according to the dimensions of the existing limbs of the Patients can be manufactured individually. This allows the Properties as well as the visual appearance of the joint remaining joint of the patient can be adjusted. The functionality for the patient can be significantly improved.

It is special in practice for this advantageous if the limbs in the rapid prototyping process, in particular can be produced by a laser sintering process. This allows the Limbs can be produced in a relatively short time. The required in each case Link properties can according to the wishes of the patient are made individually. In particular, biocompatible materials are used.

Another particularly promising variation is achieved in that the joint is part of living Has tissue. These, for example, are grown outside the body and by means of a carrier material in the desired shape brought joint components allow a high degree of compatibility with the existing limbs and also have properties that are not possible with materials that are not important for the body are reachable.

It is also particularly advantageous if the Actuator the muscle strength of the body Muscle fibers can be used. As a result, the actuator can its size considerably be reduced by essentially transferring this serves an impulse while the actual application of force by the remaining or the body's own Muscle fibers is reached.

The invention leaves various embodiments to. One of them is to clarify its basic principle shown in the drawing and is described below. This shows in an extended position in

1 a side view of two links of a joint according to the invention;

2 in the 1 links shown in a reduced view, in one for transmission large forces certain position.

1 shows an artificial joint according to the invention 1 , in particular of an artificial wrist, foot, knee, hip or shoulder joint, in a substantially force-free, stretched position. Two links are only shown in sections 2 . 3 of the joint 1 by a viscoelastic connecting element 4 are interconnected. Due to the low force transmission in the position shown, there is between adjacent articular surfaces 5 . 6 the limbs 2 . 3 a joint space 7 available, the gap width b reaches its maximum. In this position the limbs 2 . 3 therefore not only to be pivoted relative to one another about an axis perpendicular to the plane of the representation, but also to be twisted about a longitudinal axis or to be pivoted about further axes, the mobility being ensured by the elastic properties of the connecting element 4 is determined.

An extended position of the limbs suitable for the transmission of large forces 2 . 3 shows a reduced view of the joint 1 in 2 , By means of the traction means, which are only indicated in a hint 8th . 9 In this position, the tensile forces introduced are no longer present in 1 shown joint gap 7 so that the adjacent articular surfaces 5 . 6 the limbs 2 . 3 lie flat against each other. As a result, large holding forces can be achieved with a reduced degree of freedom of the joint 1 can be easily transferred.

Claims (12)

Artificial joint ( 1 ), especially an artificial hand, consisting of several articulated links ( 2 . 3 ), whereby at least one traction means movable by means of an actuator ( 8th . 9 ) to bend and stretch the limb ( 2 . 3 ) is provided, characterized in that the individual links ( 2 . 3 ) by an elastic connecting element ( 4 ) are connected to each other in such a way that a joint gap ( 7 ) between the limbs ( 2 . 3 ) by introducing a tensile force into at least one of the traction means ( 8th . 9 ) of the limb ( 2 . 3 ) can be reduced. Artificial joint ( 1 ) according to claim 1, characterized in that the joint gap ( 7 ) regardless of a bent or extended position of the limb ( 2 . 3 ) can be determined. Artificial joint ( 1 ) according to claims 1 or 2, characterized in that the joint ( 1 ) with decreasing gap width (b) of the joint gap ( 7 ) also has a reduced number of degrees of freedom. Artificial joint ( 1 ) according to at least one of the preceding claims, characterized in that the joint gap ( 7 ) is reduced to zero when a predetermined tensile force is reached, adjacent joint surfaces ( 5 . 6 ) the limbs ( 2 . 3 ) lie flat against each other. Artificial joint ( 1 ) according to at least one of the preceding claims, characterized in that the connecting element ( 4 ) consists of a viscoelastic material, in particular silicone. Artificial joint ( 1 ) according to at least one of the preceding claims, characterized in that the traction means ( 8th . 9 ) are made of nylon. Artificial joint ( 1 ) according to at least one of the preceding claims, characterized in that the actuator is designed as a linear drive. Artificial joint ( 1 ) according to at least one of the preceding claims, characterized in that the joint ( 1 ) the limbs ( 2 . 3 ) has a supporting base carrier, which supports several of the movement of the links ( 2 . 3 ) unaffected and by the traction means ( 8th . 9 ) has mutually attachable basic elements. Artificial joint ( 1 ) according to at least one of the preceding claims, characterized in that the links ( 2 . 3 ) can be individually manufactured according to the dimensions of the patient's existing limbs. Artificial joint ( 1 ) according to at least one of the preceding claims, characterized in that the links ( 2 . 3 ) can be produced in the rapid prototyping process, in particular by means of a laser sintering process. Artificial joint ( 1 ) according to at least one of the preceding claims, characterized in that the joint ( 1 ) Has components of living tissue. Artificial joint ( 1 ) according to at least one of the preceding claims, characterized in that the muscle power of the body's own muscle fibers can be used by means of the actuator.