DE102022132352A1 - Joint socket for a joint prosthesis - Google Patents

Abstract

The invention relates to a joint socket (2) intended for a joint prosthesis (1) and fixable in a bone structure (6), having a socket insert (3). The joint socket (2) has a cylindrical outer contour in its basic form. On a section facing away from an opening of the joint socket (2), the outer contour is designed in the shape of a circular tube as a peripheral edge and thus forms a projection (7) facing a bone structure (6) shown only as an example. The projection (7) is concentric with the socket insert (3) and is inserted into a groove-shaped recess (9) in the bone structure (6) to fix the joint socket (2), which recess encloses the socket insert (3) concentrically on the circumference with a small radial distance. In this way, the projection (7) forms an annular sleeve around the socket insert (3), whereby the load-bearing capacity of the bone structure (6) weakened due to the loss of substance as a result of the depression (8) in the bone structure (6) for the socket (2) is compensated by absorbing both radial spreading forces due to the fixation of the socket (2) and external forces and the bone structure (6) is not subjected to any further load.

Description

The invention relates to a joint socket for a joint prosthesis which can be fixed in a bone structure and has a socket insert for receiving an at least partially spherical joint body.

Joint prostheses with anchoring parts that can be screwed into the bone substance are already known in various designs and applications, especially in hip joint prostheses. The joint socket is inserted with the tapered side first into a surgically prepared depression in the bone.

In practice, conical or spherical joint sockets are usually used, each of which has a metallic outer shell and an insert or inlay arranged in the shell, which is usually made of ceramic, plastic or metal.

One advantage of using spherical cups is that less bone substance from the pelvic bone needs to be removed when pre-milling the spherical recess than with a conical cup. Milling itself is also easier with spherical cups, as orientation has only a small influence.

In addition to the standard design of the spherical cups, which corresponds to a hemisphere, press-fit designs are also used. The press-fit cups are slightly flattened at the pole and slightly larger in diameter than the pre-milled hemispherical bed in the bone. This ensures that the cup fits snugly in the pre-milled bone. A rough surface coating on the usual shells made of metals such as pure titanium makes it easier for the bone cells to grow onto the implant. This should ensure optimal stabilization.

In contrast to the screw cups, the spherical cups without thread and especially the press-fit cups are hammered or pressed into the pre-milled bed in a linear movement.

From the EP 0 169 978 B1 is an endoprosthesis for a hip joint socket consisting of an inner socket body and an outer shell, suitable for cement-free anchoring, in which the socket body is provided with a conical shell and the outer shell with a cavity adapted to the shell, with the outer shell and the socket body being held together by a locking structure. Several slots are evenly distributed around the circumference of the outer shell, with the surface of the outer shell being provided with a structure consisting of projections. The projections are pin-shaped and placed on the surface of the expansion socket.

From the EP 0 242 633 B1 is an endoprosthesis for a hip joint socket consisting of an inner socket body and an outer shell, suitable for cement-free anchoring, which has a structure consisting of several peripheral rows of projections in the area of the outer shell surface facing the equator. The projections are shaped like thorns and arranged on concentric circles on the surface of the expansion socket.

The DE 35 18 246 A1 refers to an acetabular cup prosthesis with a tapered outer shape for insertion into a correspondingly shaped hole in a bone, the taper of the tapered shape being designed for permanent engagement with the surrounding bone.

In the DE 29 25 089 A1 In the known joint prosthesis, an inner cup and an outer ring are provided, wherein the cup is subjected to an annular bandaging load which is exerted on the cup by the outer ring either directly or by means of a possibly interposed intermediate ring piece which is arranged between the cup and the ring.

The DE 33 47 983 C2 relates to a joint socket prosthesis, with a shell that can be fixed to a bone and with an insert that can be inserted into the shell and is composed of two bearing segments that enclose the joint ball without any division, whereby a slotted ring can be elastically expanded so that it can be pushed over the joint ball.

The EN 10 2006 019 620 B4 refers to an artificial joint socket with a number of radial through-holes for the passage of a bone screw to anchor the socket in the adjacent bone area.

A disadvantage of the current state of the art is that the bone implants weaken the bone substance due to the necessary indentations, resulting in an increased risk of possible fractures. This is particularly true for revision operations, which are usually associated with further loss of bone substance.

A particular disadvantage of expansion cups for hip joint prostheses is that the projections on the expansion cup are arranged in such a way that Forces acting in the bone tissue against the implantation direction of the expansion cup can cause the expansion cup to detach from the bone tissue.

A particular disadvantage is the direction of the fixation forces, which in most fixation options used in practice are essentially directed radially outwards, so that spreading forces arise. These spreading forces can be a cause of a reduction in the holding force of the joint socket in the bone structure, which is not uncommon.

The invention is based on the object of creating a way to largely compensate for the unavoidable weakening of the bone substance through the design of the joint socket, so that the load-bearing capacity of the bone structure is not reduced but improved. In particular, the introduction of radial spreading forces into the bone structure surrounding the joint socket should be avoided.

This object is achieved according to the invention with a joint socket according to the features of claim 1. The further embodiment of the invention can be found in the subclaims.

According to the invention, a joint socket is therefore provided in which the joint socket has at least one projection facing the bone structure, intended for engagement in a groove-shaped recess in the bone structure which is radially spaced from the recess for the socket insert in the bone structure, which projection encloses the socket insert circumferentially, in particular concentrically, with a small distance, wherein the projection has at least in sections a convex outer surface, delimited by an outer ring-shaped closed contour, and a concave inner surface, delimited by an inner ring-shaped closed contour, so that the projection with the outer surface and the inner surface can be inserted into the groove-shaped recess in a form-fitting manner and the outer surface and the inner surface each rest against a wall surface delimiting the groove-shaped recess.

The invention is based on the knowledge that the load-bearing capacity of the bone structure, which has been weakened due to the loss of substance for accommodating the joint socket, can be restored by having one or more projections of the joint socket enclose the socket insert according to the principle of a ring clamp or a cuff. In particular, the introduction of radial spreading forces into the bone structure surrounding the joint socket should be avoided.

The effect according to the invention is based on the fact that the load-bearing capacity of the bone that accommodates the joint socket, for example the pelvic bone, is improved by the forces that act transversely to the axis, namely on the one hand the spreading forces due to the inserted joint socket and on the other hand due to the external force, in particular as a result of the joint load, can be reliably absorbed by the projection, thus avoiding additional forces in the bone structure. For example, bending forces of the bone are also absorbed by the at least one projection absorbing expansions in the plane of the bone surface. For the first time, the prosthesis can therefore also absorb tensile forces transversely to the symmetry axis of the joint socket. This creates a clamp in the surface and the enclosed area that supports the shell insert remains free from unwanted force effects. At the same time, the achievable fixing forces of the joint socket are also increased, so that it remains reliably fixed even under heavy loads and does not detach from the bone structure because the holding forces in the bone are significantly increased. It has been shown that the fixation can even prevent the progression of a fracture of the bone structure and that the joint socket remains securely fixed even if such a fracture occurs. Due to the significantly increased holding forces compared to the state of the art, the bone structure to be removed can be kept to a minimum.

It has already proven to be particularly advantageous if the projection is closed in a ring shape and encloses the pan insert on the circumference. This means that the effect of the circumferential clamping is independent of direction, which at the same time simplifies the fixation of the projection in the groove-shaped recess. In practice, the resulting clamping forces already lead to sufficient fixation.

In addition, it is particularly promising if the projection has a circular cross-section with a constant wall thickness and encloses the joint socket concentrically. Due to the rotationally symmetrical design of the circular tubular or conical projection, the achievable holding forces are independent of the angular position, so that the joint socket can be used in any angular position, thus making the operation easier. A crown drill, preferably in conjunction with a depth stop, can be used in a particularly simple manner to create the groove-shaped recess, so that the effort associated with using milling tools is eliminated.

In another, also particularly useful modification of the invention, several projections are arranged within an annular region delimited by the outer contour and by the inner contour, spaced apart from one another in the circumferential direction. This allows several, preferably geometrically matching projections to be used for fixation in order to further increase the fixing forces. For this purpose, the projections can have angles or bends on the front side that penetrate the bone structure when the joint socket is rotated. Furthermore, the projections can transmit increased clamping forces if at least some of the projections are adjustable, for example, in order to brace them within the recess against the delimiting wall surfaces.

Particularly preferably, a plurality of projections spaced apart from one another are arranged evenly distributed around the circumference so that the holding forces are introduced into the bone structure evenly over the entire circumference.

The neighboring projections can have a different geometry and also a different length. However, it is particularly advantageous if the axial extension of the projection is constant in the circumferential direction and/or the axial extension of neighboring, in particular all, projections is the same, so that the joint socket safely reaches a depth position within the bone structure specified by the groove-shaped recess and this is maintained permanently.

Furthermore, according to another useful modification of the invention, the at least one projection can be fixed in different positions in the axial direction parallel to the axis of symmetry of the joint socket, in particular continuously. This allows the depth position of the joint socket to be adjusted using the projection, so that optimal positioning can be achieved. By setting the axial depth position differently for several projections distributed around the circumference, a desired angle of inclination of the joint socket can also be set if required.

In practical testing, it has already proven to be expedient if the radial distance of the projection relative to the pan insert is between 0.5 mm and 10 mm, the depth of the groove-shaped recess is between 5 mm and 35 mm and the distance between the convex outer surface and the concave inner surface is between 1 mm and 5 mm.

A further, particularly advantageous embodiment of the invention is achieved when the at least one projection has ingrowth openings on its outer surface and/or its inner surface. These ingrowth openings, also referred to as ingrowth bays, promote the ingrowth of the surrounding bone substance and after a short time form undercuts with the joint socket, which is thereby reliably fixed.

A variant of the invention has already proven to be particularly promising, in which the joint socket has a holding frame with a passage width smaller than the great circle diameter of the socket insert. As a result, a spherical joint body inserted into the socket insert is secured by the holding frame, thus preventing dislocation of the joint.

Preferably, the passage width can be expanded to the great circle diameter against an elastic restoring force of the holding frame, so that the joint body is secured in the socket insert according to the principle of a snap lock.

By having a bottom side of the joint socket facing the bone structure within the recess, which bottom side is inserted into the recess at a distance from the bone structure in the implanted position, a gap is created so that the fixation forces are introduced into the recess of the bone structure exclusively or at least largely by means of the projection.

• 1 eine vorderseitige perspektivische Darstellung einer erfindungsgemäßen Gelenkpfanne;
• 2 eine rückwärtige perspektivische Darstellung einer erfindungsgemäßen Gelenkpfanne;
• 3 eine vorderseitige perspektivische Darstellung einer Knochenstruktur mit einer Vertiefung für einen Pfannen-Einsatz der Gelenkpfanne und mit einer konzentrischen nutenförmigen Aussparung;
• 4 eine Schnittdarstellung der in der 3 gezeigten Knochenstruktur mit der Vertiefung für den Pfannen-Einsatz der lateralen nutenförmigen Aussparung;
• 5 eine vorderseitige perspektivische Darstellung der in der 3 gezeigten Knochenstruktur mit der darin fixierten Gelenkpfanne;
• 6 eine Schnittdarstellung der in der 5 gezeigten Knochenstruktur mit der darin fixierten Gelenkpfanne:
• 7 eine vorderseitige perspektivische Darstellung einer weiteren erfindungsgemäßen Gelenkpfanne;
• 8 eine rückwärtige perspektivische Darstellung der in 7 gezeigten Gelenkpfanne;
• 9 eine vorderseitige perspektivische Darstellung einer weiteren erfindungsgemäßen Gelenkpfanne;
• 10 eine rückwärtige perspektivische Darstellung der in 9 gezeigten Gelenkpfanne;
• 11 eine perspektivische Darstellung eines Halterahmens;
• 12 die in 9 dargestellte Gelenkpfanne, die in einer Knochenstruktur verankert ist;
• 13 eine Schnittdarstellung der in 12 gezeigten Knochenstruktur mit der darin fixierten Gelenkpfanne;
• 14 eine perspektivische Darstellung einer weiteren erfindungsgemäßen Gelenkpfanne mit einem exzentrisch ausgeführten Pfanneneinsatz;
• 15eine Schnittdarstellung der in 14 gezeigten Knochenstruktur mit der darin fixierten Gelenkpfanne.

The invention allows for various embodiments. To further clarify its basic principle, one of them is shown in the drawing and is described below. This shows in

• 1 a front perspective view of an acetabular cup according to the invention;
• 2 a rear perspective view of an acetabular cup according to the invention;
• 3 a front perspective view of a bone structure with a recess for a socket insert of the acetabulum and with a concentric groove-shaped recess;
• 4 a sectional view of the 3 shown bone structure with the recess for the cup insert of the lateral groove-shaped recess;
• 5 a front perspective view of the 3 shown bone structure with the joint socket fixed in it;
• 6 a sectional view of the 5 shown bone structure with the joint socket fixed in it:
• 7 a front perspective view of another joint socket according to the invention;
• 8th a rear perspective view of the 7 shown acetabulum;
• 9 a front perspective view of another joint socket according to the invention;
• 10 a rear perspective view of the 9 shown acetabulum;
• 11 a perspective view of a holding frame;
• 12 in the 9 depicted acetabulum anchored in a bone structure;
• 13 a sectional view of the 12 shown bone structure with the joint socket fixed in it;
• 14 a perspective view of another joint socket according to the invention with an eccentrically designed socket insert;
• 15one Sectional view of the 14 shown bone structure with the joint socket fixed in it.

A joint prosthesis 1 with a joint socket 2 according to the invention, which includes a socket insert 3 for receiving a joint body (not shown), is described below with reference to the 1 to 13 explained in more detail. The socket 2 has a cylindrical outer contour 4 in its basic form. On a section facing away from an opening 5 of the socket 2, the outer contour 4 is designed as a circular tubular peripheral edge and thus forms a projection 7 facing a bone structure 6 shown only as an example. The projection 7 is concentric to the socket insert 3, as can be seen in particular in the 4 and 5 The projection 7 serves to fix the joint socket 2 in a recess 8 intended for the socket insert 3 and is for this purpose inserted into the bone structure 6 in a groove-shaped recess 9 of the bone structure 6 which radially encloses the recess 8, whereby the projection 7 encloses the socket insert 3 concentrically with a small radial distance. For this purpose, the projection 7 with its convex outer surface 10 and its concave inner surface 11 can be applied force-fittingly against a respective wall surface of the groove-shaped recess 9. The projection 7 thus forms a clamping sleeve around the socket insert 3, whereby the load-bearing capacity of the bone structure 6, which has been weakened for the joint socket 2 due to the loss of substance as a result of the recess 8 in the bone structure 6, is restored by absorbing both radial spreading forces due to the fixation of the joint socket 2 and external forces and the bone structure 6 is not subjected to any further load. As can be seen in particular in the 1 , 2 and 5 As can be seen, the projection 7 has on its outer contour 4 several ingrowth openings 12 into which the surrounding bone substance 6 grows and thereby forms an undercut fixing the joint socket 2.

As particularly in the 6 and 13 As can be seen, a lower side 13 of the joint socket 2 is fixed in the bone structure 6 within the recess 8 in the implanted position at a distance A from the bone structure 6 in order to concentrate the force introduction on the projection 7.

In 11 A holding frame 14 is shown, which is inserted into the 9 , 10 , 12 and 13 in an assembled position. The holding frame 14 has a smaller passage width D than the great circle diameter of the socket insert. As a result, a spherical joint body inserted into the socket insert is secured by the holding frame, so that a luxation of the joint is prevented. The holding frame 14 in turn has two projections 7', which are connected to the projections 7 of the joint socket 2 so as to be flush with the contour, as shown in the 9 and 10 recognizable.

In the 14 and 15 is a further variant of a further joint socket 2 according to the invention with an eccentrically designed socket insert 3 in a perspective view and in a sectional side view. The joint socket 2 has a cylindrical outer contour 4 in its basic form with a circular ring-shaped edge as a projection 7, which is arranged concentrically to the outer contour 4 of the socket insert 3. A receptacle 16 for a joint ball (not shown) is not coaxial, but eccentrically arranged with respect to the outer contour 4 with an offset V of a central axis 17 of the receptacle 16 with respect to a central axis 15 of the joint socket 2, so that different edge distances R, r result in different circumferential sections. By changing the angular position of the projection 7 within the, for example, in the 13 The groove-shaped recess 9 shown in FIG. 1 allows the central axis 17 of the receptacle 16 to be optimally aligned and positioned relative to the bone structure 6 in a simple manner. The recesses designed as ingrowth openings also serve as tool receptacles 18 for the manual transmission of the rotational movement of the joint socket 2.

LIST OF REFERENCE SYMBOLS

1

Joint prosthesis

2

Articular socket

3

Pan insert

4

Outer contour

5

Opening

6

Bone structure

7

head Start

8th

deepening

9

Recess

10

Exterior surface

11

Inner surface

12

Ingrowth opening

13

bottom

14

Holding frame

15

Central axis

16

Recording

17

Central axis

18

Tool holder

A

Distance

D

Passage width

V

Offset

r, R

Edge distance

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 0169978 B1 [0007]
• EP 0242633 B1 [0008]
• DE 3518246 A1 [0009]
• DE 2925089 A1 [0010]
• DE 3347983 C2 [0011]
• DE 102006019620 B4 [0012]

Claims (13)

A joint socket (2) for a joint prosthesis (1) which can be fixed in a bone structure (6) and has a socket insert (3) for receiving a joint body which is at least partially spherical, characterized in that the joint socket (2) has at least one projection (7) facing the bone structure (6) and intended for engagement in a groove-shaped recess (9) in the bone structure (6) which is radially spaced from the depression (8) for the socket insert (3) in the bone structure (6), which encloses the socket insert (3) on the circumference, in particular concentrically, wherein the projection (7) has at least partially a convex outer surface (10) and a concave inner surface (11), so that the projection (7) with the outer surface (10) and the inner surface (11) can be inserted into the groove-shaped recess (9) in a form-fitting manner. Articular cavity (2) after Claim 1 , characterized in that the projection (7) is annularly closed and encloses the pan insert (3) on the circumference. Articular cavity (2) after Claim 1 or 2 , characterized in that the projection (7) is tubular, in particular circular tubular, and concentrically encloses the pan insert (3). Joint socket (2) according to at least one of the preceding claims, characterized in that a plurality of projections (7) are arranged spaced apart from one another in the circumferential direction within an annular region delimited by the outer contour and by the inner contour. Articular cavity (2) after Claim 3 , characterized in that several projections (7) spaced apart from one another are arranged evenly distributed around the circumference. Joint socket (2) according to at least one of the preceding claims, characterized in that the axial extension of the projection (7) in the circumferential direction is constant and/or the axial extension of adjacent, in particular all, projections coincide. Joint socket (2) according to at least one of the preceding claims, characterized in that the at least one projection (7) can be fixed in different positions, in particular continuously, in the axial direction parallel to the axis of symmetry of the joint socket (2). Joint socket (2) according to at least one of the preceding claims, characterized in that the radial distance of the projection (7) relative to the socket insert (3) is between 0.5 mm and 10 mm and/or the distance between the convex outer surface (10) and the concave inner surface (11) is between 1 mm and 5 mm. Joint socket (2) according to at least one of the preceding claims, characterized in that the joint socket (2) and/or the at least one projection (7) has ingrowth openings (12) on its outer surface (10) and/or its inner surface (11). Joint socket (2) according to at least one of the preceding claims, characterized in that the joint socket (2) has a holding frame (14) with a passage width (D) that can be changed, in particular against an elastic restoring force, and is smaller than the great circle diameter of the socket insert (3). Joint socket (2) according to at least one of the preceding claims, characterized in that the joint socket (2) has a bottom side (13) facing the bone structure (6) within the recess (8), which can be inserted at a distance from the bone structure (6) in the implanted position. Joint socket (2) according to at least one of the preceding claims, characterized in that a receptacle (16) for a joint ball is arranged eccentrically with respect to the outer contour (4) with an offset (V) of a central axis (17) of the receptacle (16) with respect to a central axis (15) of the joint socket (2). Joint socket (2) according to at least one of the preceding claims, characterized in that the socket insert (3) and the projection (7) are made in one piece and/or in one piece, in particular from a plastic.

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