DE29804880U1 - Hip prosthesis - Google Patents

Description

Hip joint prosthesis

The invention relates to a hip joint prosthesis with a socket and with a retaining plate that can be detachably connected to the socket and that comprises an annular receptacle for the socket and at least one retaining tab.

Such hip joint prostheses are used to implant sockets without cement; the socket is attached via the retaining tabs, which are fixed to the bone using bone screws, for example.

The retaining plates must in turn be firmly and permanently connected to the socket, and in known hip joint prostheses this is done, for example, by screwing (DE 41 02 510 Al; MRS-Titan hip joint socket from Peter Brehm) or by screwing a separate fastening ring into the ring-shaped receptacle of the retaining plate (EP 0 591 594 Al). With all of these types of fastening it is necessary to provide additional parts which complicate the construction of the hip joint prosthesis and also make the operation itself more difficult.

The object of the invention is to improve a generic hip joint prosthesis so that the connection between the socket and the retaining plate is simplified.

A 54 335 u

16 March 1998

u-241 - 2 -

This object is achieved according to the invention in a hip joint prosthesis of the type described at the outset in that the ring-shaped receptacle has a support surface on its inner side that tapers conically in the direction of insertion of the socket, that the socket has a contact surface on its outside that is complementary to the support surface, and that clamping means are provided that press the socket into the receptacle. The conical design of the contact surface and the support surface results in reliable mounting of the socket in the receptacle, and it is sufficient to tighten the clamping means in order to achieve reliable mounting of the socket through this receptacle.

In particular, it can be provided that the conicity of the support surface and the contact surface is selected in such a way that self-locking occurs when the socket is pressed in. In order to achieve this, only very small angles of inclination of the conical support surface and the conical contact surface are used, for example in the order of between 1 and 10°, preferably in the order of between 3 and 6°.

The clamping devices can be designed in such a way that they only press the cup into the holder once when it is inserted; this position is then maintained by the self-locking mechanism. · >·

However, it is also possible for the clamping devices to maintain the tension permanently, and then it is advantageous if the clamping devices are arranged on the pan and on the holder itself.

A 54 335 u

16 March 1998

u-241 - 3 -

In particular, it can be provided that the clamping means comprise clamping elements which, when the pan is rotated in the holder, slide along one another along a path inclined relative to the plane of rotation and, in doing so, increase the forces pressing the pan into the holder. It is then sufficient to rotate the pan in the holder to force the pan into the holder and thereby fix it in this position.

In particular, in a particularly preferred embodiment, it can be provided that projections projecting radially outwards are arranged on the pan as clamping elements and that clamping surfaces are arranged on the receptacle, which engage behind the projections when the pan is inserted into the receptacle.

It is advantageous if the projections are arranged at the narrower end of the contact surface and the clamping surfaces at the narrower end of the support surface.

Longitudinal grooves may be provided in the support surface for the passage of the projections.

It is advantageous if the clamping surfaces are directly connected to the longitudinal grooves.

In particular, the clamping surfaces can rise in the circumferential direction from the longitudinal grooves in the insertion direction.

In order to clamp the pan into the holder, it is advantageous if the pan has contact surfaces for a turning tool.

A 54 335 u

16 March 1998

u-241 - 4 -

In particular, recesses can be arranged on the edge of the pan for the engagement of a turning tool.

Usually, the edge of the pan will run parallel to the contact surface, but designs are also conceivable in which the edge of the pan runs parallel to the contact surface.
the contact surface is inclined.

The following description serves to provide further explanation in conjunction with the drawing. It shows:

Fig. 1 a view of a hip joint prosthesis

from the open side of the pan
seen;

Fig. 2 . a sectional view along line 2-2 before

assembling the individual parts of the
hip joint prosthesis;

Fig. 3 a side view of the retaining plate and

the pan during the clamping process;

Fig. 4 a view of the hip joint prosthesis of the

Fig. 3 in the direction of arrow A in
Fig.3;

Fig. 5 is a view similar to Fig. 3 with a

Pan whose edge runs parallel to the contact surface and

Fig. 6 is a view similar to Fig. 5 with a

Pan whose edge opposite the contact surface
runs inclined.

A 54 335 u

16 March 1998

u-241 - 5 -

The hip joint prosthesis 1 shown in the drawing essentially comprises three parts, namely a socket 2 that is essentially hemispherical on the outside, a joint insert 3 that can be inserted into the open interior of the socket 2 and a holding plate 4 with an annular receptacle 5 and holding tabs 6 protruding from it.

The socket 2 and the hip joint prosthesis 1 can be designed in any way, as is known per se for hip joint sockets, for example the socket 2 can be made of metal, the joint insert 3 of a plastic, in particular of polyethylene or ceramic.

It is essential that the pan 2 has an annular conical contact surface 7 on its outside, which expands towards the open side of the pan 2, with an angle of inclination that is relatively small and is, for example, between 1 and 10°, preferably between 3 and 6°. The contact surface 7 only extends over a relatively small height of the pan 2, and can be directly adjacent to the edge 8 of the pan 2 (Fig. 3), but it can also be a small distance from the edge 8 (Fig. 5). The contact surface 7 runs parallel to the edge 8 in the embodiments of Figures 3 and 5, in the embodiment of Fig. 6 the contact surface 7 is inclined relative to the edge 8.

The ring-shaped receptacle 5 of the holding plate 4 is designed on its inside as a conical support surface 9, the shape of which is complementary to the shape of the contact

·*

A 54 335 u

16 March 1998

u-241 - 6 -

surface 7 of the pan 2. This makes it possible to
Insert the pan 2 into the holder 5 so that the contact surface
7 and support surface 9 lie flat against each other. If the conicity angle is chosen to be small, this system can be self-locking, ie when the
Pressing the pan 2 into the holder 5 results in
in the contact area of the contact surface 7 and the support surface 9 a self-locking connection, which ensures that
the pan 2 is permanently fixed in the holding plate 4
is.

In the embodiments shown in the drawing, the pan 2 has projections 11 which project radially outwards at the end 10 of the contact surface 7 facing away from the edge 8 and which are arranged against one another in the circumferential direction.
are offset, for example by a circumferential angle
of 60°. These projections 11 are outwardly projecting lobes which extend only slightly in the radial direction
extend beyond the contact surface 7.

The number of projections 11 can be equal to
the number of longitudinal grooves 12, but it is also
possible to choose the number of projections 11 less
than the number of longitudinal grooves 12. For example,
three projections 11 are provided on a pan, each offset by 120°, whereas the receptacle 5 has six projections 11 each offset by 60° in the circumferential direction.
offset longitudinal grooves 12.

In the support surface 9 are distributed over its circumference
Longitudinal grooves 12 are machined, which are transverse to the plane of the
Holding plate 4 and parallel to the insertion direction of the
pan and which are distributed in the circumferential direction in the same way as the projections 11 on the pan

A 54 335 u

16 March 1998

u-241 - 7 -

2. The cross-section of the longitudinal grooves 12 is selected such that when the pan 2 is inserted, the projections 11 can pass through the longitudinal grooves 12.

In the circumferential direction, the longitudinal grooves on the side 13 of the holding plate 4 facing away from the edge 8 are adjoined by clamping surfaces 14 which are inclined relative to the plane of the annular receptacle 5 and rise from the longitudinal grooves 12 in the insertion direction.

When inserting the pan 2 into the holding plate 4, the projections 11 pass through the longitudinal grooves 12 and come into contact with the clamping surfaces 14 as soon as the pan 2 is rotated in the plane of the annular holder 5. When rotating further, the projections slide along the inclined clamping surfaces 14 and thereby press the pan 2 strongly into the annular holder 5, so that the contact surface 7 is clamped against the support surface 9; with the appropriate conicity, this creates a self-locking connection.

In order to enable the pan 2 to be rotated in the ring-shaped receptacle 5 using a tool, several insertion openings 15 are provided in the edge 8, into which a turning tool can engage. In an alternative embodiment, it is also possible to insert a screwing tool into a central receptacle opening 16 in the pan 2, which engages with a non-circular part in a complementary recess 17. This recess 17 and the part engaging in it can be designed as a hexagon, for example. With such a tool, it is also possible to press the pan in and simultaneously rotate it, so that a self-locking connection is created.

A 54 335 u

16 March 1998

u-241 - 8 -

The combination of a self-locking cone connection on the one hand and a bayonet-type clamping device on the other hand results in a permanent fixation of the pan 2 in the holder 5, since the self-locking also ensures that the bayonet-type clamping device cannot come loose, and this in turn maintains the clamping forces that create the self-locking connection. These two properties therefore influence each other in the sense of a permanent fixation, whereby no further parts are required for fixation, in particular no screws or screw-in rings.

Claims (11)

A 54 335 u 16 March 1998 u-241 - 9 - PROTECTION CLAIMS 1. Hip joint prosthesis with a socket and with a holding plate which can be detachably connected to the socket and which comprises an annular receptacle for the socket and at least one holding tab, characterized in that the annular receptacle (5) has on its inside a support surface (9) which narrows conically in the insertion direction of the socket (2), that the socket (2) has on its outside a contact surface (7) which is complementary to the support surface (9) and that clamping means (11, 14) are provided which press the socket (2) into the receptacle (5). 2. Hip joint prosthesis according to claim 1, characterized in that the conicity of the support surface (9) and the contact surface (7) is selected such that self-locking occurs when the socket (2) is pressed in. 3. Hip joint prosthesis according to one of claims 1 or 2, characterized in that the clamping means comprise clamping elements (11, 14) which, when the socket (2) is rotated in the receptacle (5), slide along one another along a path inclined relative to the plane of rotation and thereby increase the forces pressing the socket (2) into the receptacle (5). 4. Hip joint prosthesis according to claim 3, characterized in that as clamping elements on the socket A 54 335 u 16 March 1998 u-241 - 10 - (2) radially outwardly projecting projections (11) and clamping surfaces (14) are arranged on the holder (5) which engage behind the projections (11) when the pan (2) is inserted into the holder (5). 5. Hip joint prosthesis according to claim 4, characterized in that the projections (11) are arranged at the narrower end of the contact surface (7) and the clamping surfaces (14) are arranged at the narrower end of the support surface (9). 6. Hip joint prosthesis according to one of claims 4 or 5, characterized in that longitudinal grooves (12) for the passage of the projections (11) are provided in the support surface (9). 7. Hip joint prosthesis according to claim 6, characterized in that the clamping surfaces (14) directly adjoin the longitudinal grooves (12). 8. Hip joint prosthesis according to claim 7, characterized in that the clamping surfaces (14) rise in the circumferential direction starting from the longitudinal grooves (12) in the insertion direction. 9. Hip joint prosthesis according to one of the preceding claims, characterized in that engagement surfaces (15; 17) for a turning tool are arranged on the socket (2). 10. Hip joint prosthesis according to claim 9, characterized in that recesses (15) for the engagement of a turning tool are arranged on the edge (8) of the socket (2). A 54 335 u 16 March 1998 u-241 . - 11 - 11. Hip joint prosthesis according to one of the preceding claims, characterized in that the edge (8) of the socket (2) is inclined relative to the contact surface (7).