DOUBLE MOBILITY PROTHESE

Abstract

Provided is a joint replacement with a joint socket (10) having a concave joint surface (11), and with a joint insert (20) having a concave joint surface (21) and a convex joint surface (22) which are each delimited by a peripheral edge (23, 24). The convex joint surface (22) of the joint insert (20) is designed, in the assembled state, to form a first partial joint with the concave joint surface (11) of the joint socket (10). Moreover, the concave joint surface (21) of the joint insert (20) is designed, in the assembled state, to form a second partial joint with the convex joint surface (32) of a joint head (30). The joint socket (10) and the joint insert (20) each have a securing means (12, 25, 26) for preventing dislocation of the joint replacement.

Claims

1-11. (canceled)

12. A joint replacement with a joint socket (10) having a concave joint surface (11), and a joint insert (20) having a concave (21) and a convex (22) joint surface, which are each delimited by a peripheral edge (23, 24), the convex joint surface (22) of the joint insert (20) being designed, in the assembled state, to form a first partial joint with the concave joint surface (11) of the joint socket (10), the concave joint surface (21) of the joint insert (20) being designed, in the assembled state, to form a second partial joint with the convex joint surface (32) of a joint head (30), and the joint socket (10) and the joint insert (20) each having a securing means (12, 25, 26) for preventing dislocation of the joint replacement.

13. The joint replacement according to claim 12, wherein a region (12, 25) of the concave joint surface (11, 21) of the joint socket (10) and/or of the joint insert (20) prevents dislocation of the respective partial joint by forming the respective joint into an enarthrodial joint.

14. The joint replacement according to claim 13, wherein the opening diameter (D.sub.Po, D.sub.Eo) of the concave joint surface (11, 21) is 1% to 6%, preferably 2% to 5%, most preferably 3.5% to 5% less than the joint diameter (D.sub.Pi, D.sub.Ei).

15. The joint replacement according to claim 13, wherein the securing means (12, 25, 26) of at least one of the partial joints has two preferably detachable securing elements which cooperate to prevent dislocation of the partial joint.

16. The joint replacement according to claim 14, wherein the securing means (12, 25, 26) of at least one of the partial joints has two preferably detachable securing elements which cooperate to prevent dislocation of the partial joint.

17. The joint replacement according to claim 15, wherein the two securing elements cooperate by means of a preferably detachable threaded, locking and/or snap connection.

18. The joint replacement according to claim 15, wherein a securing element is formed by a preferably peripheral recess (26) to accommodate a securing ring in the concave joint surface (11, 21) of the joint socket (10) and/or joint insert (20).

19. The joint replacement according to claim 17, wherein a securing element is formed by a preferably peripheral recess (26) to accommodate a securing ring in the concave joint surface (11, 21) of the joint socket (10) and/or joint insert (20).

20. The joint replacement according to claim 15, wherein a securing element is formed by at least one recess in the joint socket (10) and/or joint insert (20), which forms a bayonet connection with a protrusion of a further securing element.

21. The joint replacement according to claim 17, wherein a securing element is formed by at least one recess in the joint socket (10) and/or joint insert (20), which forms a bayonet connection with a protrusion of a further securing element.

22. The joint replacement according to claim 18, wherein a securing element is formed by at least one recess in the joint socket (10) and/or joint insert (20), which forms a bayonet connection with a protrusion of a further securing element.

23. The joint replacement according to claim 12, wherein the joint socket (10) and/or the joint insert (20) comprises an insertion aid (27, 28), with which the insertion of the respective convex joint surface (22, 32) into the corresponding concave joint surface (11, 21) is enabled.

24. The joint replacement according to claim 13, wherein the joint socket (10) and/or the joint insert (20) comprises an insertion aid (27, 28), with which the insertion of the respective convex joint surface (22, 32) into the corresponding concave joint surface (11, 21) is enabled.

25. The joint replacement according to claim 15, wherein the joint socket (10) and/or the joint insert (20) comprises an insertion aid (27, 28), with which the insertion of the respective convex joint surface (22, 32) into the corresponding concave joint surface (11, 21) is enabled.

26. The joint replacement according to claim 23, wherein the insertion aid (27) is formed as a preferably elongate recess in the convex joint surface (22, 32) of at least one of the partial joints.

27. The joint replacement according to claim 23, wherein the insertion aid (27) is formed in a plane of symmetry of the convex joint surface (22, 32).

28. The joint replacement according to claim 26, wherein the insertion aid (27) is formed in a plane of symmetry of the convex joint surface (22, 32).

29. An implantable joint component, in particular a joint insert (20) for a double joint or a joint head (30), with an insertion aid according to claim 23.

30. An implantable joint component, in particular a joint insert (20) for a double joint or a joint head (30), with an insertion aid according to claim 26.

31. An implantable joint component, in particular a joint insert (20) for a double joint or a joint head (30), with an insertion aid according to claim 27.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0044] Embodiment examples will now be described in detail with reference to the following Figures and description in order to provide a better understanding of the present invention. To this end, the features as are apparent from the Figures will be denoted by reference numbers. The same reference numbers will be used for different embodiment examples provided that the features in these embodiment examples are alike or achieve a similar effect.

[0045] FIG. 1 shows an assembled joint replacement according to the invention, comprising two partial joints.

[0046] FIG. 2 shows a joint insert according to the invention, configured as an enarthrodial joint, during insertion of a joint head mounted on a prosthesis stem.

[0047] FIGS. 3a and 3b show an insert according to the invention which has an insertion aid on its convex joint surface.

[0048] FIGS. 4a and 4b show an implantable joint socket according to the invention.

[0049] FIGS. 5a and 5b show the insertion of a joint insert according to the invention by means of an insertion aid configured in an elongate shape.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0050] FIG. 1 shows the assembled state of a double-joint hip endoprosthesis which is also termed double mobility prosthesis. As already described above, prior art prostheses of this kind, despite having a small femoral head 3, provide the degree of movement of a large-head prosthesis. The implant, shown in the abduction position in FIG. 1, combines the advantages of less abrasion due to a smaller femoral head with the greater degree of movement provided by a large-head prosthesis as it is composed of two partial joints.

[0051] The first partial joint is situated between the hip socket 1 implanted in the pelvic bone and a joint insert 2. The second partial joint is formed between the joint insert 2 and the femoral head 3. As can be recognized in FIG. 1 from the deflection of the implant at a maximum abduction angle, the degree of movement is increased in that the prosthesis stem 4, situated below the femoral head 3, abuts against the rim of the joint insert 2 which, however, is deflected due to the movability of the first partial joint, as a result of which the degree of movement is increased until the prosthesis stem 4 abuts against the inner edge of the hip socket 3.

[0052] In the implant shown in FIG. 1, the first partial joint has, between the hip socket 1 and the joint insert 2, joint components of a ball joint which fall apart if no longer held together by external forces. By contrast, the second partial joint between the joint insert 2 and the femoral head 3 is an enarthrodial joint. In this joint, the joint insert 2 encloses the femoral head 3 beyond the equator thereof and is thus mounted thereon in such a way that the two joint components of the second partial joint will not fall apart even without the stabilizing impact of external forces.

[0053] FIG. 2 shows a hip endoprosthesis according to the invention during insertion of the femoral head 30 into the joint insert 20. In this process, the joint head 30, which is connected to the prosthesis stem 40, is inserted into the concave joint surface 21 of the joint insert 20 by means of a pressing tool 50. A joint blocking means 13 ensures that, while the joint head 30 is being pressed in via the peripheral edge 23 of the concave surface 21 of the joint insert 20, the joint insert 20 cannot swivel relative to the joint socket 10 during use of the tool 50. For this purpose, the joint blocking means 13 is secured, as described further below, via a connecting element 14 to the rim 15 of the joint socket 10 which is situated between the exterior surface 17 of the joint socket 10 and the concave interior surface 11 of the joint socket or connects these. While being fastened in this manner, a portion of the joint blocking means extends above and beyond the rim of the joint insert 20 which is situated between the peripheral edge 23 of the concave joint surface 21 and the peripheral edge 24 of the convex joint surface 22. Advantageously, said portion of the joint blocking means 13 extends at an angle greater than 180° relative to the annular rim of the joint insert 20 in order to prevent dislocation of the joint insert in every direction.

[0054] It goes without saying that it is possible to provide such a joint blocking means 13 also for the joint head 30 in order to simplify the insertion of the joint head 30 into the concave joint surface 21 of the joint insert 20.

[0055] If the assembly of one or both partial joints is performed after implantation of the joint socket, the joint blocking means 13 may moreover be adapted to be used as an abutment by the pressing tool 50. With this type of configuration, the pressing tool is supported on the blocking means 13 so that ideally no force is applied to the surrounding bone tissue.

[0056] Furthermore, it can be recognized from FIG. 2 that, in its neutral position, i.e. when the rotational symmetry axes of the joint insert 20 and the joint socket 10 are superimposed on each other, the rim of the joint insert 20 is flush with the rim 15 of the joint socket 20. It is possible just as well to allow the peripheral edge of the joint insert 20 to protrude from the edge 15 of the joint socket 20 in the neutral position or starting position. As a result, the frequency of movement between the joint socket 10 and the joint insert 20 can be increased while maintaining the same degree of movement. In other words, deflection of the joint head 30 will cause the prosthesis stem 40 to contact the peripheral edge of the joint insert 20 earlier, and thus a forced relative movement between the insert 20 and the joint socket 10 will occur earlier as well. Since this may lead to increased abrasion, as is described above, the embodiment shown in FIG. 2 is preferred.

[0057] FIGS. 3a and 3b show a joint insert 20 according to the invention. As can be recognized from FIG. 3b, the concave joint surface 21 of the joint insert 20 is formed as an enarthrodial joint. The same applies to the concave joint surface 11 in the sectional view of the joint socket 10 shown in FIG. 4b. Consequently, the concave receptacle in both partial joints has an insertion opening smaller than the convex joint surface to be received therein, and therefore the assembly of the partial joints requires the use of force and/or an insertion aid 27.

[0058] Since, in the embodiment example shown in FIGS. 3 and 4, both partial joints have a spherical shape, the radius R.sub.Ei of the concave joint surface 21 is larger than the radius of the opening of the receptacle formed by the concave joint surface 21, and the diameter D.sub.Pi of the concave joint surface 11 of the joint socket 10 is greater than the diameter D.sub.Po of the joint socket opening.

[0059] Not only is the joint insert 20 in FIGS. 3a and 3b configured as an enarthrodial joint in the region of the concave joint surface 21, but it moreover has an additional securing means in the region 25 extending beyond the equator which is in the form of a recess 26 directed towards the opening of the concave joint surface 21. This means is provided for insertion of a securing ring. In the shown embodiment example, the joint insert 20 is thus designed to have two securing means on the side of the second partial joint, which prevent separation of the convex joint surface 32 of the joint head 30 from the concave joint surface 21 of the joint insert 20. However, it is possible just as well to provide just one of the securing means 25, 26 in order to prevent dislocation of the respective partial joint.

[0060] An elongate strip made of a flexible material is preferably used as the securing ring. Preferably, the elongate strip is preformed in a C-shape. In order to introduce the securing ring into the peripheral recess 26, it is pushed lengthwise into the recess 26 through an access opening or access recess extending from the rim of a concave joint surface 11, 21 to the recess 26. Where the flexible C-shaped securing ring is not preformed, it will take on the C-shape only upon introduction into the peripheral recess 26. As an alternative, it is also possible to use a circlip as the securing ring.

[0061] Furthermore, the joint insert 20 as shown in FIGS. 3a and 3b has an insertion aid 27 in the form of an elongate groove on the side of the first partial joint, i.e. on the convex surface 22 of the joint insert 20. This groove 27 extends from the peripheral edge 24 of the convex joint surface 22 via the pole 29 and back to the peripheral edge 24. The points of contact of the groove 27 with the peripheral edge 24 are diametrically opposed to each other in the shown embodiment example since the insertion aid 27 is situated in a plane of symmetry of the spherical convex joint surface 22.

[0062] The joint socket 10 as shown in FIGS. 4a and 4b, which forms the receptacle for the first partial joint, has a spherical-segment-shaped concave joint surface 11 as well as an exterior surface 17 provided for implantation into the bone tissue of a patient. The exterior surface 17 may be anchored in the bone tissue by means of different techniques known from the prior art. As already described above, the joint socket 10 as well as the joint insert 20 have a region 12 which, as a securing means, prevents dislocation of the first partial joint, i.e. prevents the joint insert 20 from popping out.

[0063] Furthermore, fastening means 18 are provided in the peripheral region formed between the exterior surface 17 and the concave joint surface 11 of the joint socket 10. In the present embodiment example, the fastening means 18 are a threaded hole and two stop holes, by means of which the joint blocking means 13 of FIG. 2 is detachably fastened via a connecting element 14. As can be seen from FIGS. 2 and 4, the threaded hole 18 of the joint socket 10 is situated on the circumference of the peripheral region, offset in each case by 90°, between said two diametrically opposed stop holes.

[0064] It will now be explained with reference to FIGS. 5a and 5b how an insertion aid 27 assists the insertion of a joint insert 20 into a joint socket 10. However, anything stated below and above also applies directly to the partial joint formed by the concave joint surface 21 of the joint insert 20 and the convex joint surface 32 of the joint head 30.

[0065] FIGS. 5a and 5b show a joint insert 20 according to the invention during insertion into a joint socket 10. In the present embodiment example, the joint socket 10 and the joint insert 20 are components of a double mobility hip joint endoprosthesis. The joint socket 10 has an inner concave joint surface 11 that cooperates with the convex joint surface 22 of the joint insert 20. The opening of the concave joint surface 11 of the joint socket 10 is delimited by a peripheral edge 16, and its diameter is smaller than the diameter of the concave joint surface 11 at the height of the equator of the joint socket 10.

[0066] As can furthermore be recognized from FIGS. 5a and 5b, the convex joint surface 22 of the insert 20 has an insertion aid 27 situated in a plane of symmetry of the insert 20 or the convex joint surface 22. The shown insertion aid 27 is configured as an elongate recess extending from the peripheral edge 24 towards the pole 29 of the convex joint surface 22. The elongate recess 27 is situated in the plane of symmetry of the convex joint surface 22, indicated by the auxiliary line 28.

[0067] Given that the insertion aid 27 extends as far as up to the peripheral edge 24 of the convex surface 22, it is possible to facilitate the transportation of synovial fluid between the convex surface 22 of the insert 27 and the concave surface 11 of the socket 10 as well as the removal of possible abrasion products between these surfaces, and thus to increase the service life of the joint endoprosthesis.

[0068] The elongate recess starts at the peripheral edge 24 of the convex surface 22 and extends, in FIGS. 5a and 5b, over approximately one third of the length of the auxiliary line between the pole 29 and the edge 24. Preferably, the elongate recess extends over 25% to 75% of the length of the connecting line. However, as can be recognized from FIGS. 3a and 3b, the recess 27 may also extend over the entire convex joint surface of one joint part.

[0069] It will be understood that the elongate recess does not necessarily have to be in contact with the peripheral edge 24 of the convex surface 22, but may also be arranged with both ends in the convex surface 22 of the joint insert 20. Furthermore, the insertion aid 27 may be configured to include multiple components. For instance, it is possible to provide a further component of the insertion aid 27 on the opposite side of the joint surface 22, symmetrically to the insertion aid 27 shown in FIG. 5a.

[0070] The longer and broader the insertion aid 27, the easier it is for the joint insert 20 to be inserted into a joint socket 10 configured as an enarthrodial joint. It should be noted, however, that as the length and/or width increases, the convex surface of the insert becomes more irregular, which may entail a local increase in tension.

[0071] The shape of the recess is preferably configured to match the contour of the edge of the associated concave joint surface that serves as the mating joint part of the partial joint. When placed against the joint socket 10, the recess of the insertion aid 27 with its bottommost section comes into contact, preferably at least via a section of its recess base, with the peripheral edge 16 of the concave receptacle of a mating joint part, here the joint socket 10. Most preferably, the recess 27 has in its longitudinal direction a contour with a radius that is substantially the same as the radius R.sub.Pi of the joint socket 10 at its peripheral edge 16. Preferably, the insertion aid 27 gradually merges, at least at one of its ends in the longitudinal direction, into the convex surface of the insert.

[0072] The cross-section of the elongate recess is configured to prevent peak stresses being generated in the region of the transition from the insertion aid 27 to the joint surface 22. For this reason, it is preferred for the insertion aid to seamlessly merge into the convex joint surface 22 of the joint insert 20.

[0073] In the shown embodiment, the recess-shaped insertion aid 27 is disposed on the auxiliary line 28 between the edge of the convex joint surface 22 and its pole 29. In other words, the plane formed by the recess makes an angle of 0° with the plane defined by the auxiliary line 28. Even though this is the preferred embodiment, it is easily possible to select any other angle.

[0074] In other words, the angle between the insertion aid 27 and the auxiliary line 28 may range from 0° to 90°, preferably, however, from 0° to 45°, and even more preferably from 0° to 15°. The principle generally applies that the smaller the angle between the insertion aid 27 and the imaginary auxiliary line 28, the lower the probability that the insertion aid 27 will become flush with the opening edge of the joint socket during movement of the joint, which may give rise to dislocation.

[0075] As an alternative, it is possible to offset the plane defined by the insertion aid 27 in parallel to the plane defined the auxiliary line 28 and/or the plane of symmetry of the convex joint surface 22.

[0076] Such free positioning of the insertion aid 27 on the convex surface 22 of the insert 20 permits optimization in terms of ease of mounting of the joint insert 20 in a joint socket 10 or of a joint head 30 in a joint insert 20. This makes it possible to take into account the strain still imposed, despite the insertion aid 27, on the implant material during assembly of the artificial joint. It is also possible to reduce the strain imposed on the material of the joint socket 10, the insert 20 and/or the joint head 30 depending on the implantation site and the strain resulting therefrom. Thus, the insertion aid 27 makes it possible to produce the joint socket 10 and particularly the joint insert and/or the joint head 30 from a relatively inelastic material such as, for example, metal or ceramics.

[0077] Since in the shown embodiment, the insertion aid 27 is arranged on the auxiliary line 28, i.e. in a plane of symmetry of the joint insert 20, and thus at an angle of 0°, insertion of the joint insert 20 into the joint socket 10 is performed by tilting the two components relative to one another by about 90° prior to insertion. If the insertion aid 27 is arranged at a different angle, the joint socket 10 and the joint insert 20 must correspondingly be oriented differently with respect to one another so as to allow assembly.

[0078] After orientation, the insertion aid 27 is placed on the peripheral edge 26 of the concave joint socket surface 11 such that the peripheral edge 16 is disposed within the recess of the insertion aid 27. In this way, the insert 20 is situated, in the plane of the opening of the concave joint surface 11, at a position slightly offset relative to the mounted state, and thus fits through the opening formed by the concave joint surface 11. To put it differently, the offset compensates for the oversize of the joint insert 20 in proportion to the opening of the joint socket 10.

[0079] In other words, the joint insert 20 fits into the concave joint surface 11 of the joint socket 10 since, owing to the depth of the insert aid 27, the diameter of the joint insert 20 is smaller than or equal to the diameter of the peripheral edge 16 of the concave joint surface 11 at the height of the peripheral edge 24 of the convex surface 22 of the joint insert 20.

[0080] In FIG. 5b, the joint insert 20 is shown in a slightly inclined position after its successful insertion into the joint socket 10. Furthermore, it can be recognized that the joint insert 20 of this embodiment example has a concave joint surface 21 provided for receiving a joint head 30 (see FIG. 2).

[0081] In any case, the present invention provides a joint endoprosthesis which, while being dislocation-free, is easy to assemble during surgery.

REFERENCE NUMERALS

[0082] 1 Joint socket (prior art) [0083] 2 joint insert (prior art) [0084] 3 joint head (prior art) [0085] 4 joint stem (prior art) [0086] 10 joint socket [0087] 11 concave joint surface of the joint socket [0088] 12 means for securing the joint socket: protrusion [0089] 13 joint blocking means [0090] 14 connecting element [0091] 15 peripheral rim of the joint socket [0092] 16 peripheral edge of the joint socket [0093] 17 exterior surface of the joint socket [0094] 18 fastening means [0095] 20 joint insert [0096] 21 concave joint surface of the joint insert [0097] 22 convex joint surface of the joint insert [0098] 23 peripheral edge of the concave joint surface of the joint insert [0099] 24 peripheral edge of the convex joint surface of the joint insert [0100] 25 means for securing the joint insert: protrusion [0101] 26 means for securing the joint insert: recess for securing ring [0102] 27 insertion aid: recess [0103] 28 auxiliary line on the convex joint surface of the joint insert 20 which extends in the plane of symmetry thereof [0104] 29 pole of the convex joint surface 22 [0105] 30 joint head [0106] 32 convex joint surface of the joint head [0107] 40 prosthesis stem [0108] 50 pressing tool [0109] Aq equator of a convex or concave joint surface [0110] R.sub.P1 inner radius of the joint socket [0111] D.sub.P1 inner joint diameter of the joint socket [0112] D.sub.P0 joint opening diameter of the joint socket [0113] R.sub.E1 inner radius of the joint insert [0114] D.sub.E0 inner joint diameter of the joint insert [0115] D.sub.Ei joint opening diameter of the joint insert