WO1996004867A1

WO1996004867A1 - Artificial joint, in particular artificial human hip joint

Info

Publication number: WO1996004867A1
Application number: PCT/EP1995/003164
Authority: WO
Inventors: Dietmar Kubein-Meesenburg; Hans NÄGERL; Peter Adam
Original assignee: Theusner, Joachim
Priority date: 1994-08-10
Filing date: 1995-08-09
Publication date: 1996-02-22
Also published as: JPH10504212A; DE4428290A1; EP0774936A1; AU3258195A; DE19580850D2

Abstract

An artificial joint, in particular for replacing human joints, consists of at least two parts with functional surfaces movable in relation to each other. The functional surfaces of the joint parts (1, 2) are spherical, toroidal and/or rotationally symmetrical. In use, i.e. in their operational position, a linear force transmission area KL is formed between the joint parts (1, 2).

Description

Artificial joint, in particular artificial human hip joint

The present invention relates to an artificial joint for replacing in particular human joints, consisting of at least two joint parts with functional surfaces that move towards one another, namely a joint head and an articular socket, the joint having at least three degrees of freedom of movement. In the case of three joint parts, a joint head, a pressure distribution body and a joint socket, the joint has five degrees of freedom.

In the known artificial joints, in particular artificial human joints, there is basically a small radius difference between the joint socket and the joint head, so that the joint head can be inserted into the joint socket so that there is point contact between these two joint parts. This point-like contact is expanded upon compression of the joint parts by elastic deformation of the materials to a small circular area on which there is a high contact pressure, so that such wear is high stressed artificial joint parts is present. This results in a limited durability of the artificial joint parts.

In the known artificial joints there is still the problem of friction. Since the joints do not circulate, a hydrodynamic liquid film cannot usually form, so that liquid lubrication does not start and dry friction is given. The body fluid can also only wet the parts of the joint head that protrude from the joint socket. This leads to high wear and thus to a limited durability of the artificial joint parts. In addition, dry friction results in abrasion of the surfaces sliding against one another. The foreign particles produced in this way place a particular burden on the living organism.

The object of the present invention is to increase the durability of artificial joint parts, in particular of artificial human joints.

This is achieved according to the invention in that the functional surfaces of the joint parts are spherical and / or toroidal and / or rotationally symmetrical and are designed in a linear force transmission area between the contacting functional surfaces in the inserted state, ie in the functional position. Rotations¬ symmetrical means that there are contours rotated about an axis of rotation. As a result, according to the invention, the pressure at the point of the force transmission is significantly reduced at the same force transmission, which results in a considerably reduced material load and a reduced material abrasion. Thus, according to the invention Lifespan of the artificial joint parts increased considerably. According to the invention, the line-shaped power transmission area can be circular, ellipsoidal, trapezoidal or else horseshoe-shaped. The design of the linear force transmission area is essentially determined by the prevailing, special functional directions. According to the invention, a linear force transmission area is obtained, for example, by contacting a spherically shaped joint surface with a toroidally shaped joint surface or two toroidally shaped joint surfaces. The formation of a line-shaped force transmission area according to the invention brings advantages both with artificial joints with three and with five degrees of freedom.

When forming a joint with five degrees of freedom, such as is known from German patent application P 39 08 958.4, in which a pressure distribution body is arranged between the joint head and the joint socket, the formation of the linear contact can be provided both between the joint socket and the pressure distribution body and between the pressure distribution body and the joint head.

According to the invention, the joint parts can be designed such that access to body fluid is achieved in the center of the joint. According to the invention, such access to body fluid is obtained by forming a hole in the center of the socket. This allows the body's own synovial fluid to penetrate from the center into the joint space between the joint parts. This hole is advantageously circular. When forming a joint with five degrees of freedom, As is known, for example, from German patent application P 39 08 958.4, in which a pressure distribution body is arranged between the joint head and the joint socket, the formation of a hole in the joint socket and in the pressure distribution body opens up the additional possibility of lubrication of the joint surfaces. A sliding film is produced which significantly reduces the wear between the joint parts. The formation of a hole in the socket also has the advantage that after a healing phase in the hole area, the body's own connective tissue and / or cartilaginous structures arise which not only reduce the problem of friction, but also increase the stability of the socket in the pelvis.

So that the reduction in contact pressure according to the invention is particularly effective, the relative dimensioning of the radii of curvature of the articular surfaces at the contact point is important. This dimensioning depends on the materials used. With metal-to-metal contact, it can therefore be advantageous that the radii of curvature differ only slightly. The radius difference can be, for example, less than 2% to a few parts per thousand of the larger radius.

Advantageous embodiments of the invention are contained in the subclaims.

The invention is explained in more detail with reference to the exemplary embodiments illustrated in the accompanying drawings.

Show it: 1 to

14 different exemplary embodiments of an artificial joint according to the invention in cross section through the pivot point of the respective joint.

1 that an artificial joint according to the invention is formed from an artificial joint head 1 and an artificial joint socket 2. When used as an artificial hip joint for humans, the socket 1 is the fossa and the joint head 2 is the condyle. In the embodiment shown, the socket 1 and the joint head 2 form a ball joint with three degrees of freedom, the pivot point of which is P. The radius R _{x of} the joint head 1 and that of the joint socket 2 are virtually the same except for a small gap. A hole 3 can be formed in the joint socket 2 in such a way that the center of the hole 3 lies in the main line of action of the artificial joint in the basic joint position. The main line of action is indicated by XX.

Through the hole 3 there is access to body fluid from the pelvic side. In addition, by filling the hole with connective or cartilage tissue through the healing process after the operation, the joint socket is of course expanded. Since this natural expansion of the joint socket is relieved of force, because the joint force is distributed over the artificial part of the joint socket 2, lubrication is also possible from the central region of the joint, which supports the formation of a lubricating film on the entire condyle surface. Because at the same time as the wetted area of the joint head is enlarged through the hole, the area of the joint socket to be wetted is significantly reduced, and in particular the respective lubrication path limited. This can significantly reduce wear due to abrasion in the joint.

The size of the hole can form 1/6 to 5/6 of the socket area up to its equator, so that the opening angle a can be changed accordingly. The size of the opening angle a depends on the material pairing of the materials of the joint head 1 and the joint socket 2. The shape of the hole 3 is circular in the illustrated embodiment. However, the present invention is not limited to this, in particular an ellipsoidal, trapezoidal or else horseshoe-shaped hole shape can also be provided. Through this hole 3 there is also a linear force transmission area K _L between the joint head

1 and the socket 2 in the edge region of the hole, thus increasing the force transmission region. With the same power transmission, the pressure at the location of the power transmission is reduced, and this results in a significantly reduced material load.

The joint shown in FIG. 1 is a ball joint with three degrees of freedom. However, the present invention can also be used in a joint with five degrees of freedom, as is known from German patent application P 39 08 958.4, reference being made to this patent in its entirety. The illustration in the attached FIG. 2 serves to explain this. The joint shown is between the socket

2 and the joint head 1, a pressure distribution body 4, a so-called pressure distribution body 4, is arranged. The joint head 1 has a center of rotation M _: and the socket 2 has a center of rotation M _; , The circular, convex cutting contour of the joint head 1 has the radius Ri and the concave, circular sectional contour of the joint socket 2 have the radius R ₂ . The pressure distribution body 4 has a thickness D on the extension of the connecting line between M _x and M ₂ . The pressure distribution body 4 has sliding surfaces 5, 6, the radii of which correspond to those of the adjoining surfaces of the socket 2 and the joint head 1. The radius R of the link axis path of the dimeric link chain with two link axes through the two rotation centers M _λ and M ₂ is

R = R ₂ - R _λ - D,

ie R has a positive amount, so that R ₂ > R _x + D.

According to the invention, the joint socket 2 can have a hole 3 which is designed corresponding to the hole 3 in FIG. 1 and can be arranged accordingly. Furthermore, it is expedient if a hole 7 is also formed in the pressure distribution body 4.

This configuration of the socket 2 and the pressure distribution body 4 also lubricates the contact surfaces between the pressure distribution body 4 and the joint head from the center. This ensures a uniform formation of the lubricating film between all surfaces sliding on one another. This design of the joint socket 2 and the pressure distribution body 4 also produces linear force transmission regions in the edge region of the holes between the adjacent joint parts with the reduction in pressure already described at the location of the respective force transmission and the resulting reduced material load. In the following figures, the same parts as in Figs. 1 and 2 are provided with the same reference numerals.

3 shows an embodiment of an artificial joint according to the invention. Here, the joint head 1 is spherical with a circular cutting contour and the radius R _: in P. The socket 2 is, seen mathematically, a toroid. Its axis of rotation is X-X. The circular cutting contours with the centers M ₂₁ and M ₂₂ and the associated radii R _2: and R ₂₂ represent mathematically the toroid-producing circle which is rotated about the ration axis XX to produce the toroid surface. R ₂₁ is therefore equal to R ₂₂ :

R ₂ is therefore the radius of the toroid generating circle. R _λ <R ₂ also applies. R _τ is an outer torus radius. It is defined by the point on the toroidal surface that has the greatest distance from the axis of rotation XX. The contact line K _L is a circle. The associated center lies on the axis of rotation XX of the toroid. The radius is R ₃ . ß is a cone angle to the contact radius R ₃ . The joint socket can contain a hole in the lower part which allows the entry of liquid and thus helps to increase the lubrication of the joint.

3, which is drawn in the basic position, represents a ball joint with three degrees of freedom. The joint head can only rotate about the pivot point P, which in this example is also the geometric center of the joint head. The following also applies: R _τ = R ₂ - (R _a - R _x ) ^• sin (ß / 2); R ₃ = R _α ^• sin (ß / 2).

The angle β determines the position and size of the contact circle K _L. Its size depends on the materials chosen for the articular surfaces. As a rule, an angle β = 90 ° is particularly advantageous.

The radius difference δ R = (R ₂ - R, between the toroid-producing radius R ₂ and the radius R _{λ of} the joint head ball is generally small. It can be, for example, less than 2% up to a few parts per thousand of R _2. In this In one embodiment, the joint surface of the socket does not necessarily have to be a torus, it can also be the concave surface of another body with rotational symmetry in the sectional view.

FIG. 4 shows a variant of the joint design according to FIG. 3. Here again the joint head 1 is spherical with a circular cutting contour around the pivot point P, the circular cutting contour having the radius R _λ around P. The socket 2 represents a toroid. To generate it, the toroid-generating circle is rotated with R ₂ about the axis of rotation XX. In the sectional view, two convex, circular socket contours 9, 10 with the center points M ₂₁ and M ₂₂ and the radius R _{2 are created} . The contact line K _L is a circle. The associated center lies on the axis of rotation XX of the toroid. The radius is R ₃ . ß is the cone angle to the contact radius R ₃ . 4, which is drawn in the basic position, represents a ball joint with three degrees of freedom. The joint head can only rotate about the pivot point P, which in this example is also the geometric center of the joint head. If the resulting force adjuster extends outside the angular range of ß, the joint changes into a joint with five degrees of freedom. The following also applies:

R _τ = R ₂ - (R ₂ + R _x ) • εin (ß / 2); R ₃ = R_ ^• sin (ß / 2).

5 shows a further alternative of an artificial joint according to the invention. In this embodiment, the joint head 1 is toroidal and the socket 2 is spherical. Their concave, circular arc-shaped cutting contour has the center point P and the radius R ₂ . In the sectional view, the toroidal joint head 1 has two circular, convex contours with the radii R _1X and R ₂₂ , which are given by the toroid-generating circle R.

R ₁ = R _1X = R ₁₂ (centers M _ι:, M ₁₂ ).

Here R,> R,

Otherwise, the same radii and angles as in the previous figures are shown.

A hole 3 is again formed in the joint socket 2, specifically in the manner described for FIG. 1. In this embodiment, the linear force transmission area is formed on the joint head. The following applies: R _τ = R _u + (R ₂ - R_) ^• sin (ß / 2); R ₃ = R ₂ ^• sin (ß / 2).

5, which is drawn in the basic position, represents a ball joint with three degrees of freedom. The joint head can only rotate about the pivot point P, which in this example is simultaneously the geometric center of the socket 2 . In principle, it also applies here that instead of a toroid, another rotationally symmetrical body can be used as the joint head 1.

The radius difference δ R = (R ₂ - R _λ ), between the radius R _{2 of} the spherical socket and the radius R _A. of the toroidal joint head is generally small. For example, it can be less than 2% to a few parts per thousand of R ₂ .

In this embodiment, the articular surface of the articulated head 1 does not necessarily have to be a torus. It can also be the concave surface of another body with rotational symmetry in the sectional view. On the contact line for the radius difference δ R between the radius of the sphere and the radius of curvature of the cutting contour, the above statements apply accordingly.

6 and 7 show a further embodiment of a joint according to the invention, consisting of the joint head 1 and the joint socket 2. Here, both the joint head 1 and the socket 2 are toroidal. In the basic position (FIG. 6), both toroids have the same axis of rotation XX. The axis of rotation P of this joint is not stationary, as can be seen from FIGS. 6 and 7, with FIG. 7 in a bent position of the joint shows. The joint head 1 shows in the sectional view two convex, circular contours with the center points M _1X and M ₁₂ and the radii R _ιrt and R ₁₂ . They correspond to the circle R _x = R _1X = R ₁₂ : this in turn is the circle that creates the toroid when it rotates around the toroid axis XX. Accordingly, the sectional figure of the joint socket shows two concave, circular contours with the center points M ₂₁ and M ₂₂ and the radii R ₂₁ and R ₂₂ . They correspond to the toroid generating circle R ₂ = R ₂₁ = R ₂₂ . The connecting line of the center points M ₂₂ and M ₁₂ intersects the connecting line of the center points M ₂₁ and M _1X in the axis of rotation P.

L ₂ is the coupling element between M ₂₁ and M ₂₂ and L _x is the coupling element between M _X1 and M ₁₂ . δ R ₂ and δ R _: are the connecting rod members. The following applies:

(L ₂ - L / (2 ^• (R ₂ - R _j )) = sin (ß / 2).

δ R ₂ = δ R _x = δ R.

The formation of this joint has the advantages that the linear contact areas migrate on both joint surfaces. Furthermore, a pumping action for the joint fluid is produced, and there is a stable mechanical equilibrium in the rest position (basic position) and self-stabilization when the individual flexion positions are taken.

8 shows a further alternative of an artificial joint according to the invention. Both the joint head 1 and the joint socket 2 are designed as toroidal bodies with a common axis of rotation XX in the basic position. The joint head 1 has, in Cross-section seen, two convex, circular contours with the centers M _X1 and M ₁₂ and the radii R _X1 and R ₁₂ . They correspond to the circle R = R _1X = R ₁₂ : this in turn is the circle that creates the toroid when it rotates about the toroid axis XX. The joint socket 2 has two concave, circular contours with the center points M ₂₁ and M ₂₂ and the radii R ₂₁ and R ₂₂ in the sectional view. They correspond to the circle R ₂ = R ₂₁ = R _{22 /} with which the toroid surface can be generated. The intersection P of the connecting line M ₂₂ M ₁₂ with the connecting line M ₂₁ M _X1 is the axis of rotation of the system. The distances M ₂₂ M ₁₂ = δ R ₂ and M ₂₁ M _{ι: ι} = δ R _x are the same size. They are the connecting rods. The advantage of this joint variant is that the linear force transmission areas K _L migrate on both joint surfaces and there is a pumping action for the joint fluid, which in turn can penetrate into the joint through the hole 3 formed in the joint socket, as already described for the previous figures. However, this embodiment has an unstable equilibrium at rest. The following applies:

(L ₂ + L / (2 ^■ (R ₂ + R) = sin (ß / 2).

FIG. 9 shows a variant of FIG. 6, the joint head 1 being designed like the joint head according to FIG. 6. 4 consists of two convex socket areas 9, 10 with the center points M ₂₁ and M _{22 of} their circular sectional contours with the radii R ₂₁ and R ₂₂ , which are the same size and larger than the radii R _u and R ₁₂ . This design enables the linear contact areas to migrate on the joint parts, and a pumping action for the joint fluid is achieved. The joint shows a stable balance in the rest position. It the other sizes known from the above figures also apply here. It is:

^ 21 ⁼ ^ 22 ⁼ ^ 2 / ^' ^ 11 ⁼ ^ 12 ⁼ ^ 1

(L ₂ + L / (2 ^• (R ₂ +) = sin (ß / 2).

10 shows a further variant of an artificial joint according to the invention. The joint head 1 corresponds to the design in FIG. 5. The design of the joint socket 2 corresponds to that in FIG. 7. The radii R and R ₁₂ are the same and smaller than the radii R ₂₁ and R _{22 of} the same size. With this design, the linear contact areas migrate on both joint parts and a pumping effect for the synovial fluid is achieved. Here, however, there is an unstable equilibrium in the rest position. The following applies:

(L ₂ - L / (2 • (R ₂ - R) = εin (ß / 2).

A further joint variant of an artificial joint according to the invention is shown in FIG. 11. Here again, both the joint head 1 and the joint socket 2 are formed as toroidal bodies. The joint head 1 consists of a toroid such as the joint head in FIG. 5. The concave joint socket 2 represents a toroidal surface of the same type, the generating radius being larger. The joint socket can in turn have a hole 3. In this joint design too, the linear contact areas move on both joint parts, and there is a pumping effect for the joint fluid. There is a mechanically stable equilibrium in the rest position. The following applies: R ₂ - R ₂₁ = R ₂₂ ; R _x - R _X1 - R ₁₂ (L ₂ - L _x ) / (2 • (R ₂ - R) = sin (ß / 2).

All variants of FIGS. 1, 3-11 have three degrees of freedom of movement. The details given for the embodiment in FIG. 3 apply to the size ratios of the contacting radii in all embodiments.

In principle, all ball joints can be expanded into a joint with three artificial joint parts by connecting them in series or by inserting a second joint ball. This creates a joint that has five degrees of freedom. In this case, mechanical pressure stability of the pressure distribution body is always ensured when the pivot point P of the joint joint pressure joint pressure distribution body lies "above" the pivot point P _τ of the partial joint pressure distribution body joint head: a compression force holds the pressure distribution body mechanically stable between the joint head and joint socket .

FIGS. 12 and 13 show two exemplary embodiments of such a series connection.

FIG. 12 shows a series connection of two ball joints with "linear" force transmission consisting of the types: toroidal joint socket - spherical joint head (FIG. 3) and spherical joint socket - toroidal joint head (FIG. 5).

Three artificial joint parts are created: joint socket 2, movable pressure distribution body 4, joint head 1. P _IT is the fulcrum of the acetabular ball joint, given by the joint surfaces of the joint parts 2 and 4. The joint surface of the socket 2 is toroidal. The articulating surface of the pressure distribution body 4 is spherical and has the radius R ₂ (corresponds to FIG. 3). The articular surface of the pressure distribution body 4 articulating with the joint head 1 is spherical. Its center is Ε> _j , the associated radio is R _x . The articular surface of the articular head 1 is toroidal (corresponds to FIG. 5).

It is essential for a mechanically stable configuration that P _{I (as seen} from P _{: I} , is displaced towards the joint part 2, P thus "above" P _:. This makes it possible for the joint part 4 to be pressed out with a compressive frictional connection .

If one holds joint part 2, joint part 4 can rotate around P _TI . Joint part 1 is taken along by this rotation, but can then additionally rotate about P _j .

The distance R between the turning centers P _:: and P- is constant and represents the chain link of the dimeric link chain. The following applies:

D iεt the minimum distance of the circles around P _ι: or P- with the radii R ₂ or R and thus the minimum thickness of the pressure distribution body.

For the radii of the toroidal articular surface of the joint head 1 and the toroidal articular surface of the socket 2, the formulas of the shape according to FIG. 5 or FIG. 3. The comments made there also apply to the dimensioning of the radius ratios.

A particular advantage of this arrangement: the pressure distribution body 4 has only spherical articular surfaces. As a result, the contact rings K _L2 and K _L1 remain stationary on the joint surface of the joint socket 2 and also on that of the joint head 1 when the pressure distribution body 4 and the joint head 1 move. This has the consequence that the force transmission between the pressure distribution body 4 and the joint socket 2 can never hit a central hole in the socket.

A hole 3 in the joint surface of the socket has the advantage that synovial fluid can also penetrate into the joint from below. This increases the lubrication. The hole can also be provided for the pressure distribution body.

FIG. 13 shows the connection in series of two ball joints with "linear" force transmission of the type: spherical joint socket - toroidal joint head corresponding to FIG. 5.

Three artificial joint parts are created: joint socket 2, pressure distribution body 4, joint head 1.

P _XI is the fulcrum of the socket joint, given by the joint surfaces of the joint parts 2 and 4. The joint surface of the socket 2 is spherical and has the radius R ₂ . The articulating surface of the pressure distribution body 4 is toroidal. The one with the Joint head 1 articulating joint surface of the pressure distribution body 4 is spherical. Its center is P _τ , the associated radius is R. The articular surface of the articulated head 1 is toroidal.

It is essential for a mechanically stable configuration that P _τ , viewed from P, is displaced towards the joint part 2. As a result, it is impossible for the joint part 4 to be pressed out in the case of compressive frictional connection.

If joint part 2 is held firmly, joint part 4 can rotate around P _n . Joint part 1 is taken along by this rotation, but can then additionally rotate about P _: .

The distance R between the centers of rotation P _n and P _: is constant and represents the chain link of the dimeric link chain. The following applies:

R = R ₂ - R _j _ - D.

D is the minimum distance between the circles around P _{: ι} or P _: with the radii R ₂ or R _:.

The formulas of FIG. 3 apply analogously to the radii of the toroidal surfaces of the joint head 1 and the pressure distribution body 4 on their joint surface facing the joint socket 2.

As a result of the configuration according to the invention, the existence of the two articulating surfaces with a linear or band-shaped contact surface, the latter occurring when the two contact bodies behave elastically, creates a cavity which is defined by the contact line (band). is delimited.

This cavity is variable in the case of elastic changes in shape under loading / unloading cycles and / or by the corresponding shaping (see FIGS. 6 to 11). The variable cavity creates a suction / pumping effect for liquids that serve to lubricate the joint.

The variety of the possible combination is documented by naming two further arrangements:

a) Series connection of two ball joints with "linear" force transmission of the type: toroidal fossa - spherical condyle, corresponding to FIG. 3.

b) Series connection of a ball joint with "linear" power transmission of the type: toroidal fossa - spherical condyle (corresponding to FIG. 3) with a "normal", conventional ball joint, as is currently the case. used in arthroplasty.

14 shows that it may be expedient to close the hole 3 in the socket 2 by means of a closure body 12, the closure body 12 being screwable into the hole 3, for example. This closure body 12 serves to keep the socket 2 and the hole 3 closed during insertion, so that no bone cement can penetrate into the area of the hole 3, and after the bone cement has been inserted and hardened, the closure body 12 is removed from the region Steering pan 3 unscrewed so that it then hole 3 releases. The closure body 12 can also serve as a positioning aid when inserting the socket.

Claims

Artificial joint for replacing in particular human joints, consisting of at least two joint parts with functional surfaces moving towards each other, characterized in that the functional surfaces of the joint parts (1, 2, 4) are spherical and / or toroidal and / or rotationally symmetrical A linear force transmission area K _{L is formed} between the joint parts (1, 2, 4) and in the inserted state, ie in their functional position.

Artificial joint for replacing in particular human joints, consisting of at least two joint parts with functional surfaces that move towards each other, so that the joint parts (1,

2, 4) spherical and / or toroidal and / or are rotationally symmetrical and are designed such that in the inserted state, ie in their functional position, access to body fluid is achieved in the center of the joint.

3. Artificial joint according to claim 1 or 2, so that a hole (3) is formed in the socket (2), and preferably such that the center of the hole (3) lies in the basic force line of action of the artificial joint in the basic position.

4. Artificial joint according to one of claims 1 to 3, characterized in that the joint parts consist of a joint head (1) and a joint socket and also an interposed pressure distribution body (4) between the joint socket (2) and the joint head (1). and there is preferably a hole (7) in the pressure distribution body, the center of which lies in the basic position, in particular in the main line of action of the joint.

5. Artificial joint according to claim 3 or 4, so that the size of the hole (3) in the socket (2) is 1/6 to 5/6 of the socket surface up to its equator.

6. Artificial joint according to one of claims 3 to 5, characterized in that the hole (3) located in the joint socket (2) with a closure body (12) is in particular screwable ver¬ closable.

7. Artificial joint according to claim 1, characterized in that the joint parts consist of a joint head (1) and a joint socket (2) as well as a pressure distribution body (4) slidably arranged between the joint socket (2) and the joint head (1), of the sliding surfaces (5, 6).

8. Artificial joint according to one of claims 2 to 6, characterized in that functional surfaces of the joint parts (1, 2, 4) in the inserted state, ie in their functional position, have a linear force transmission area K _L between the joint parts (1, 2, 4 ) exhibit.

9. Artificial joint according to one of claims 1 to 8, characterized in that the joint head (1) has a center of rotation yi _x and the joint socket (2) has a center of rotation M ₂ , the circular, convex cutting contour of the joint head (1) Radius R _: and the concave, circular cutting contour of the socket (2) has the radius R ₂ and the pressure distribution body (4) has a thickness D on the extension of the connecting line between M _: and M ₂ and the radius R of the joint axis path of the dimeric joint chain two joint axes through the two centers of rotation M _x and M ₂ results from R = R ₂ - R _x - D, where R ₂ > R _x + D iεt.

10. Artificial joint according to one of claims 3 to 9, characterized in that in the socket (2) a hole (3) is formed, in such a way that the center of the hole (3) in the The main line of action of the artificial joint is in the basic joint position, the edge of the hole forming the linear force transmission area.

11. Artificial joint according to one of claims 1 to 10, characterized in that for an articulation between the joint head (1) and the pressure distribution body (4) a center of rotation P _τ and for the articulation between the pressure distribution body (4) and the socket ( 2) there is a rotation center P _n , the first articulation having a radius R _x (radius of the spherical surface of the corresponding joint surface pair) and the second articulation a radius R ₂ (radius of the spherical surface of the corresponding joint surface pair), the minimum distance D and where the radius R of the articulated axis path of the dimeric articulated chain with the articulated axes through the two centers of rotation P _x and P results from R = R ₂ - R _λ - D, where R ₂ > R _λ + D (FIGS. 12, 13 ).

12. Artificial joint according to one of claims 1 to 11, characterized in that the joint head (1) is spherical with a circular cutting contour and the radius R _x around the pivot point P of the joint and the socket (2) has a toroidal shape made up of two has intersecting, circular, concave cut contours with the center points M ₂₁ and M ₂₂ and the associated radii R ₂₁ and R ₂₂ , where R ₂₁ = R ₂₂ is and R _: <R ₂₁ is.

13. Artificial joint according to one of claims 1 to 12, characterized in that the joint head (1) is spherical with a circular cutting contour around the pivot point P and has the radius R _x , and in that the joint socket (2) is part of a torus iεt, which in the sectional image has the radius R _τ and the joint socket (2) is formed from two convex socket surfaces (9, 10) with circular cutting contours around the associated center points M ₂₁ and M ₂₂ , the center points M ₂₁ and M ₂₂ and the fulcrum P each lie in the corners of an isosceles triangle and the base line of the triangle is formed by the connecting line of M ₂₁ and M ₂₂ , the radius R _{2 being} the circular sectional contour of the socket surface (9, 10) and R _x <R ₂ .

14. Artificial joint according to one of claims 1 to 12, characterized in that the joint head (1) is toroidal and the joint socket (2) has a concave, circular arc-shaped cutting contour around the pivot point P with the radius R ₂ , the joint head (1 ) has two circular, convex sectional contours with the radii R _1X and R ₁₂ around the center points M _X1 and M ₁₂ , whereby

15. Artificial joint according to one of claims 1 to 12, characterized in that the joint head (1) and the joint socket (2) are toroidal, the axis of rotation P is not statio¬ nary and the joint head (1) from two convex, circular _{Cutting contours} with the center points M _xl and M ₁₂ and the radii R _u and R _{12 is} formed, where ^R n = ^R i ₂ i ^{st and} the joint socket (2) from two concave, circular sectional contours with the center points M ₂₁ and M ₂₂ and the Radii R ₂₁ and R _{22 is} formed, where R ₂₁ = R ₂₂ and the connecting line of M _1X and M ₂₁ and the connecting line of M ₁₂ and M ₂₂ intersect at the pivot point P and meet the contact line K _L.

16. Artificial joint according to one of claims 1 to 12, characterized in that the joint head (1) and the joint socket (2) are designed as a toroidal body, the joint head (1) seen in cross section from two circular cut contours the center points M _lx and M ₁₂ and the associated radii R _X1 and R _{12 are} formed and the joint socket (2) consists of two concave, circular sectional contours with the center points M ₂₁ and M ₂₂ and has the radii R ₂₁ and R ₂₂ , these being the same size and being larger than the radii R ₁₂ and R _11, which in turn are the same size and the connecting line of M _X1 and M ₂₁ and the connecting line of M ₁₂ and M ₂₂ intersect at the pivot point P and the contact - meet line K _L.

17. Artificial joint according to one of claims 1 to 12, characterized in that the joint head (1) and the joint socket (2) are designed as a toroidal body, the joint head (1) consisting of two convex, circular sectional contours with the center points M _u and M ₁₂ and the radii R _X1 and R _{12 are} formed, R _1X = R ₁₂ being and the joint socket (2) comprising two convex socket regions (9, 10) the center points M ₂₁ and M _{22 of} their circular sectional contours and the radii R ₂₁ and R _{22 are} formed, wherein R ₂₁ and R _{22 are the} same size and larger than the radii R _X1 and R ₁₂ .

18. Artificial joint according to one of claims 1 to 12, characterized in that the joint head (1) and the joint socket (2) are designed as a toroidal body, the joint head (1) having two circular, convex sectional contours with the radii R _1X and R _{12 has} around the center points M _X1 and M ₁₂ and the joint socket (2) is formed from two convex socket regions (9, 10) with the center points M ₂₁ and M ₂₂ with the radii R ₂₁ and R ₂₂ , which are the same are large, the radii R _1X and R _{12 being the} same size and smaller than the equally large radii R ₂₁ and R ₂₂ .

19. Artificial joint according to one of claims 1 to 12, characterized in that the joint head (1) and the joint socket (2) are designed as a toroidal body, the joint head (1) from a cutting contour with the two center points M _1X and M ₁₂ and the radii R _1X and R ₁₂ , where R _u and R _{12 are of the} same size and the joint socket (2) has two circular sectional contours with the center points M ₂₁ and M ₂₂ and the radii R ₂₁ and R ₂₂ , which are the same size, as well as the connecting line M _n , M ₂₁ intersects with the connecting line M ₁₂ , M ₂₂ at the pivot point P and these connecting lines meet the contact line K _L on the contact surfaces.

20. Artificial joint according to one of claims 1 to 12, characterized in that both the socket (2) and the joint head (1) are toroidal, and that the pressure distribution body (4) has two spherical sliding surfaces (5, 6) .