DE102007031664B4 - Structured surface of a ball head or a socket insert of an artificial hip joint to prevent dry running - Google Patents

Abstract

A ball head (2) having a convex spherical head surface and / or cup insert (3) with a cap (5) and a concave cup surface for use in a hip joint prosthesis consisting of a shaft (1) on which the ball head (2) is mountable, the ball head (2) with its ball head surface (6) is rotatably insertable on a sliding zone on the dome surface (7) in the dome (5) of the socket insert (3), and the socket insert (3) can be coupled to a hip socket (4), wherein the shaft (1) in the femur (20) and the acetabulum (4) in the pelvic bone (21) are implanted, wherein on the ball head surface (6) and / or on the Kalottenoberfläche (7) at least in the region of the sliding zone recesses arranged are, characterized in that the recesses at irregular intervals (13) on the ball head surface (6) and / or the Kalottenoberfläche (7) are arranged.

Description

The invention relates to a ball head according to the preamble of the claim 1 ,

The market has a variety of prosthetic systems for the replacement of the natural hip joint. These usually consist of a shaft with a ball head and a hip socket with pan insert. The stem and acetabulum are connected to the body by ingrowth into the femoral or pelvic bones and are carriers for the ball head or cup insert. The ball head is rotatably mounted in the cup of the socket insert - Degree of freedom: 1.

For the articulation of the ball head in the socket insert, the occurrence of hydrodynamic friction is desirable in order to keep the acting friction moments and consequently occurring loads on the joint components as well as the wear of the sliding spherical surfaces as small as possible. For this purpose, it is necessary that there is always a closed fluid film between the ball head and the cup of the socket insert in the region of the sliding zone. This forms from the existing synovial fluid and is maintained by the capillary forces acting in the joint space.

Now, due to various indications, a tearing off of the fluid film can occur, as a result of which unwanted dry running and thus dry friction occur. Possible causes exist z. As in a lack of fluid or too long joint gap, which can not be completely bridged by the acting capillary forces.

DE 103 18 374 B3 shows a ball head with a convex spherical head surface and / or socket insert with a dome and a concave dome surface for use in a hip joint prosthesis, which consists of a shaft on which the ball head is fastened, the ball head with its ball head surface on a sliding zone on the dome surface in the The cup insert of the socket insert is rotatably insertable, and the socket insert can be coupled to a hip socket, wherein the socket can be implanted in the femur and the acetabulum in the pelvic bone, wherein on the ball head surface ( 6 ) and / or on the Kalottenoberfläche recesses are arranged at least in the region of the sliding zone.

The invention has for its object to improve such a ball head so that the excitation of vibrations during sliding of the ball head surface is prevented on the Kalottenoberfläche.

According to the invention this object is achieved in that the recesses are arranged at irregular intervals on the ball head surface and / or the Kalottenoberfläche.

Recesses are arranged on the ball head surface and / or on the calotte surface at least in the region of the sliding zone. By introducing depressions into the spherical surface and / or Kalottenoberfläche liquid reservoirs form within the sliding zone, since the introduced wells form a free volume for accumulation of synovial fluid. In addition, the distance over which the capillary forces have to drive the formation of the fluid film is significantly shortened - in fact only between two liquid reservoirs. This additionally favors the formation of the fluid film. This measure prevents dry running.

In an embodiment according to the invention, the depressions are grooves. Grooves are easy to insert into the ball head surface and / or in the dome surface.

The grooves are preferably arranged on the ball head surface parallel to the equator and / or on the Kalottenoberfläche parallel to the end face of the socket insert. In an embodiment of the invention, these grooves form circumferential annular recesses. The synovial fluid can thereby spread over the entire peripheral surface.

In another embodiment, the recesses are formed as shape deviations of the ball head surface and / or the Kalottenoberfläche. This also forms liquid reservoirs within the sliding zone.

To prevent the excitation of vibrations when sliding the ball head surface on the Kalottenoberfläche the recesses are arranged according to the invention at irregular intervals on the ball head surface and / or the Kalottenoberfläche.

Advantageously, the depressions have a maximum depth T in the range of 0.05 <T <1.0 mm, particularly preferably 0.1 <T <0.5 mm.

In an embodiment according to the invention, the ball head and / or the socket insert are made of ceramic.

The introduced recesses thus provide a volume for the collection of synovial fluid to supply the sliding pair with fluid. The depressions can be introduced macroscopically as grooves or only microscopically as shape deviations from the spherical geometry. In the second case, they can only represent one kind of regular, wavy surface profile.

To prevent the excitation of vibrations, when sliding the interrupted by grooves or wave recesses spherical surface on the Kalottenoberfläche an arrangement of the grooves or wave recesses takes place irregularly on the surface.

Hereinafter, the prior art and the invention will be explained in more detail with reference to figures.

1 shows the state of the art. A hip joint prosthesis usually consists of a shaft 1 coupled with a ball head 2 and a hip socket 4 coupled with a pan insert 3 , shaft 1 and acetabulum 4 are with the body of the patient by ingrowth in the thigh 20 or pelvic bone 21 connected and are carriers for the ball head 2 or pan insert 3 , The ball head 2 is in the dome 5 of the socket insert 3 rotatably mounted.

2 shows a ball head 2 in a pan insert 3 articulated or used articulated. The other parts of the hip joint prosthesis are not shown for the sake of simplicity. The ball head 2 points to the ball head surface 6 grooves 8th on, all parallel to the equator 9 run and on the ball head surface 6 are formed circumferentially. These grooves 8th serve as liquid reservoir for the synovial fluid, so that no dry running of the sliding ball / socket insert 3 can occur.

In the embodiment shown, the grooves are 8th periodically 13 arranged or spaced from each other and not according to the invention at irregular intervals.

In the 3a and 3b is in each case a section of a section through a ball head 2 ( 3a ) and by a pan insert 7 ( 3b ). On the ball head surface 6 of the ball head 2 are form deviations 11 arranged, which serve as liquid reservoirs. These form deviations 11 may be formed microscopically small and distributed, for example, as in a golf ball on the surface. Likewise, these form deviations 11 also on the dome surface 7 the dome 5 be introduced. It may be these form deviations 11 or the grooves 8th according to 2 on the ball head surface 6 and / or the dome surface 7 be arranged.

4 shows a section of the ball head surface 6 and / or the dome surface 7 These surfaces have a wavy surface profile 12 exhibit. The valleys 14 this wavy surface profile 12 serve as liquid reservoirs.

5 shows a section of the ball head surface 6 and / or the dome surface 7 , The depth T of the grooves shown here is in the range of <0.5 mm.

All ball heads shown in the figures 2 and pan inserts 3 consist of a ceramic material.

Claims (7)

A ball head (2) having a convex spherical head surface and / or cup insert (3) with a cap (5) and a concave cup surface for use in a hip joint prosthesis consisting of a shaft (1) on which the ball head (2) is mountable, the ball head (2) with its ball head surface (6) is rotatably insertable on a sliding zone on the dome surface (7) in the dome (5) of the socket insert (3), and the socket insert (3) can be coupled to a hip socket (4), wherein the shaft (1) in the femur (20) and the acetabulum (4) in the pelvic bone (21) are implanted, wherein on the ball head surface (6) and / or on the Kalottenoberfläche (7) at least in the region of the sliding zone recesses arranged are, characterized in that the recesses at irregular intervals (13) on the ball head surface (6) and / or the Kalottenoberfläche (7) are arranged. Ball head or socket insert after Claim 1 , characterized in that the recesses are grooves (8). Ball head or socket insert after Claim 2 , characterized in that the grooves (8) on the ball head surface (6) parallel to the equator (9) and / or on the Kalottenoberfläche (7) parallel to the end face (10) of the socket insert (3) are arranged. Ball head or socket insert according to one of Claims 1 to 3 , characterized in that the depressions as shape deviations (11) of the ball head surface (6) and / or the Kalottenoberfläche (7) are formed. Ball head or socket insert according to one of Claims 1 to 4 , characterized in that the recesses form a wavy surface profile (12). Ball head or socket insert according to one of Claims 1 to 5 , characterized in that the recesses have a maximum depth (T) in the range of 0.05 <T <1.0 mm, preferably of 0.1 <T <0.5 mm. Ball head or socket insert according to one of Claims 1 to 6 , characterized in that the ball head (2) and / or the socket insert (3) consist of a ceramic.

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