WO2003020180A1

WO2003020180A1 - Artificial hip joint acetabulum

Info

Publication number: WO2003020180A1
Application number: PCT/IB2001/001507
Authority: WO
Inventors: Rudolf Koch; Maurizio Tollari
Original assignee: Biomet Merck Gmbh
Priority date: 2001-08-20
Filing date: 2001-08-20
Publication date: 2003-03-13
Also published as: EP1420724A1; WO2003020180A8

Abstract

The invention relates to an artificial hip joint acetabulum comprised of a socket (1c), which is anchored in the pelvic bone, and of an insert (3) that, when mounted, interacts with the condyle of the femoral prosthesis. The connection between the socket (1c) and the insert (3) comprises a novel anti-twist stop that is formed by placing at least two knurled teeth (2d, 2e) on the interior of the socket (1c) or on the exterior of the insert (3).

Description

Artificial hip socket

The invention relates to an artificial hip joint socket made of at least two parts which can be connected to one another.

Conventional hip joint pans consist of a socket anchored in the pelvic bone and an insert which, when assembled, interacts with the condyle of the femoral prosthesis. Often, the insert takes on another deposit, one of the two parts forms the immediate hard bearing for the head of the femoral prosthesis and the other part is usually a rather elastic link between the hard inner shell and the mostly hard pan.

In the present application, it is about the connection between the pan and the insert, regardless of whether the insert receives another deposit or is formed only in one piece.

In conventional hip joint prostheses, the connection between the pan and use z. Example by encapsulation of the insert with the material of the pan (see, for example: EP-A2-726066 and EP-B1-544214), by snap-connecting the insert with the pan (see, for example: EP-A1-242633) or by screwing the insert made with the pan or the like.

Especially with the structures with snap connection, there is the need for rotationally secure anchoring of the two parts relative to each other. In the overmolded versions, the rotation lock is automatically given. There are two variants of the bolted versions: those with locking screws and those in which a thread is formed between the socket and the insert (compare eg: EP-A1-242633). The latter is then secured against rotation when the torque occurring acts under loading by the patient in the screwing. However, if the moment acts in unscrewing or loosening direction, this could lead to a loosening of the anti-rotation device. The rotation lock between the two parts is desirable for a variety of reasons:

1. Uncontrolled friction due to relative movements between the pan and the insert can lead to uncontrolled abrasion, which is undesirable in any case. Abrasion particles may be affected by tissue effects, e.g. cause a loosening of the prosthetic seat.

2. For certain types of inserts - eg. B. those that are used for disinfestation - is also the relative rotational position of the insert to the pan critical. This relative position is set during surgery and should be maintained for the life of the prosthesis.

So far, the anti-rotation has been realized by one of the following measures:

a) Inside the pan, four symmetrically distributed projections are mounted, which correspond with opposing grooves.

b) There are also systems with pointed cones which press axially into the relatively soft material of the insert (see, for example: US-A-5092897.

c) At the front edge of the pan rib-shaped teeth are formed, which cooperate with opposing teeth on an edge of the collar superior collar of the insert, as well as in the axial direction.

d) grooves are formed in the edge region of the pan, which cooperate with opposing ribs of the insert.

e) By surface treatment, for. As sandblasting, the inner surface of the pan is roughened. The relatively rough inner surface of the pan is sufficient for frictional rotation between pan and insert, which achieves sufficient effect, however, only with conical pans. All these known different types of anti-rotation between the two parts fulfill their anti-rotation task more or less well.

For further prior art reference is made to the following documents: DE-A1-19701778

EP-A1-927547

EP-A1 -803234

EP-A1-743050

EP-B1 -698382 EP-A1-420795

EP-A1-360734

EP-A1 -242633

FR-A1 -2700686

FR-A1-2239980 US-A-5972032

US-A-5879404

US-A-5609648

US-A-5222984

US-A-5092897 US-A-5049158

US-A-4715860

However, each of the mentioned species also has disadvantages:

a) The mounted inside the pan projections and the opposite grooves on the insert must be prepared in an elaborate milling process. In addition, the rotational positions can not be selected continuously.

b) The indented pointed pins result in an insufficient anti-rotation effect. c) The formed on the front edge of the pan rib-shaped teeth that cooperate with opposing teeth on an edge of the collar superior collar of the insert are relatively expensive to produce.

d) The grooves formed in the edge region of the pan, which cooperate with opposing ribs of the insert, are also relatively expensive to produce. Both the solution c) and d) are not infinitely adjustable.

e) Sandblasting has too little effect on spherical compounds.

The invention is therefore based on the object to find a new rotary locking system which avoids the mentioned disadvantages, is easy to manufacture and has a sufficient rotational security.

This object is achieved by attaching a knurl of at least two teeth on the inside of the pan or on the outside of the insert.

This knurling is formed in particular on the harder of the two parts, so that the knurled teeth dig during assembly in the surface of each other softer part. The extent of the knurling teeth is preferably approximately axially with respect to the insertion direction, so that the knurling can be produced by axial poking with a bumping tool.

The height of the knurling teeth above the bottom of the inner diameter of the pan is about twice to three times the clearance between the pan and the insert.

Preferably, a plurality of groups of knurled teeth are distributed over the circumference of the outside of the insert or over the circumference of the inside of the pan. Particularly preferably, there are three groups, each offset by 120 ° to each other. For particularly high-torque rotation, the knurling can also be formed continuously over the entire circumference.

The knurling is preferably formed on an annular projection, which is optionally interrupted in the areas without knurling. According to a development of the invention, the knurling can also be subdivided by transverse ribs, which, in addition to the rotational security, also enable a catch in the axial direction.

According to the invention, the height of the knurling teeth is limited to a certain extent, so that penetration of the teeth into the surface structure of the respective softer part is made possible without causing a shearing material removal or unnecessarily increasing the required driving force of the insert. This effect is further promoted by the faces of the knurled teeth are flattened or rounded.

With regard to the number of knurling teeth per knurling group, the skilled person is aware of the teaching of the present application and depending on the choice of materials, as already mentioned, between at least two over at least five, at least ten, at least twenty or at least forty teeth. The shape of the teeth or the valleys between the teeth can be selected within the scope of the invention, wherein a tooth shape which is approximately triangular in cross section is preferred.

figure description

The figures are described coherently and comprehensively. Like reference numerals mean like components; Reference numerals with different indices indicate functionally identical components.

Show it:

Figure 1 shows a schematic section through a novel pan with knurled teeth;

FIG. 2 shows an enlarged detail of a variant according to FIG. 1;

FIG. 3 is a bottom view of FIG. 1;

Figure 4 is a bottom view of a variant of Figure 3;

Figure 5 is a schematic section through a system with pan, insert and insert; and

6 shows a schematic section of a variant with knurled teeth and

Transverse grooves.

Figure 1 shows schematically the section through a novel pan 1a with groups of Rändelzähnen 2a and 2b. Preferably, three groups of knurled teeth are provided, as can be seen in the view from below on FIG. 1 according to FIG. FIG. 3 shows the ladle 1a and the three groups of knurled teeth 2a, 2b and 2c. A variant of FIG. 3 is shown in FIG. 4, in which the knurling teeth 2f are arranged over the entire circumference of the pan 1d.

FIG. 2 shows an enlarged detail of a variant embodiment according to FIG. 1, in which the knurled teeth 2 b are formed on a web 9, which is delimited laterally by two recesses 6, 7. The recess 7 is formed as Schnappnute, which causes the axial securing of the insert in the pan 1 b. FIG. 5 shows a section through a system with cup 1c, groups of knurled teeth 2d, 2e, insert 3 and insert 4. The insert 4 holds in the insert 3, for example according to the patent application of the applicant WO-A 1-01 / 32108. A square 5 improves the durability, as the aforementioned WO-A1 can be removed.

FIG. 6 shows a variant in which querns 8a, 8b are arranged on the socket 1e to the knurling teeth 2g on the socket 1e. These transverse grooves cause a slight penetration of the relatively soft material of the insert in these grooves, so that in this structure also results in an axial movement assurance.

LIST OF REFERENCE NUMBERS

1a, b, c, d, e pan,

2a, b, c, d, e, f. g knurled teeth,

3 use,

4 deposit,

5 square,

6 puncture

7 snaps,

8a, b transverse grooves,

9 footbridge.

The list of reference symbols and FIGS. 1 to 6, together with the objects described or protected in the claims, are an integral part of the disclosure of this application.

Claims

1.Artificial acetabular cup, with a socket that is anchored in the pelvic bone and an insert that interacts with the joint head of the femoral prosthesis when assembled, with an anti-rotation device between the socket and the insert, characterized in that the anti-rotation device is attached by attaching at least two Knurled teeth (2) on the inside of the pan (1) or on the outside of the insert (3) is formed.

2. Artificial acetabular cup according to claim 1, characterized in that the extent of the knurled teeth (2) is approximately axial.

3. Artificial acetabular cup according to claim 1 or 2, characterized in that at least two groups of at least two

Knurled teeth (2) are distributed over the circumference of the insert (3) or over the circumference of the inside of the pan (1).

4. Artificial acetabular cup according to claim 3, characterized in that three groups of at least two knurled teeth (2a, b, c), each offset by 120 ° to one another, are distributed over the circumference.

5. Artificial acetabular cup according to one of the preceding claims, characterized in that each group has at least five knurled teeth (2).

6. Artificial acetabular cup according to one of the preceding claims, characterized in that each group has at least ten knurled teeth (2).

7. Artificial acetabular cup according to one of the preceding claims, characterized in that each group has at least twenty knurled teeth (2).

8. Artificial acetabular cup according to one of the preceding claims, characterized in that each group has at least forty knurled teeth (2).

9. Artificial acetabular cup according to claim 4, characterized in that the knurled teeth (2f) are arranged continuously over the entire circumference.