WO2008003597A1

WO2008003597A1 - Implant

Info

Publication number: WO2008003597A1
Application number: PCT/EP2007/056211
Authority: WO
Inventors: Andreas Stern
Original assignee: Aesculap Ag & Co. Kg
Priority date: 2006-07-03
Filing date: 2007-06-21
Publication date: 2008-01-10
Also published as: DE102006031573A1; DE202006010535U1

Abstract

To improve an implant comprising at least one first implant part and one second implant part, which can be joined to the first implant part via a conical connection, wherein the first implant part has a conically shaped recess, and the second implant part has a conically shaped projection which corresponds or essentially corresponds to the recess, which can be inserted into said recess, and which is fixed in a connecting position or held by a tight fit in such a way that its stability increases, it is proposed that the recess has at least one first and one second conical wall section, and that a curvature radius of the first wall section is larger than a curvature radius of the second wall section.

Description

implant

The present invention relates to an implant comprising at least a first implant part and a second implant part connectable to the first implant part by means of a conical connection, wherein the first implant part has a conically shaped recess and the second implant part has a correspondingly or substantially correspondingly shaped and insertable into the recess and has a conically shaped projection in a connection position clamped or held in a press fit.

Implants of the type described above are known, for example, in the form or as parts of hip joint endoprostheses in which the first implant part is formed, for example, by a prosthesis stem and the second implant part by a neck element. A firm connection between the two implant parts is ensured by the usually frusto-conical, ie conical projection, which is arranged on one of the two implant parts, and a recess corresponding to the projection on the other implant part.

Although excellent strength values are already achieved in known implant systems with such conical connections, it would nevertheless be desirable to further increase the strength of an implant or modular implant system comprising at least two implant parts.

It is therefore an object of the present invention to improve an implant of the type described above so that it has an increased strength.

This object is achieved according to the invention in an implant of the type described above in that the recess at least a first and a second conical wall portion and that a radius of curvature of the first wall portion is greater than a radius of curvature of the second wall portion.

The development proposed according to the invention has the advantage that the cone connection has a larger contact surface in the region of the first wall section, as a result of which, in particular, abrasion under high loads can be reduced. In addition, cross-sectional geometries of implant parts can be optimally utilized. In particular, such curvature radii of wall sections can be maximized, preferably where larger loads are expected, larger radii of curvature for the wall sections of the cone connection can be selected. In addition, the choice of different radii of curvature of the wall sections has the advantage that a connection between the two implant parts is unique to each other. On additional elements to ensure a clear connection of the two implant parts together, for example in the form of additional projections and recesses, which ensure a clear connection according to the known key-lock principle, can be dispensed with. The cone connection thus fulfills a dual function.

It is advantageous if the first wall section merges directly into the second wall section. Thus, the projection on the second implant part can be made particularly compact.

In order to further increase stability of the connection of the two implant parts of the implant, it is advantageous if the first wall section is opposite to the second wall section or substantially opposite. Furthermore, as well as a highly symmetrical configuration of the projection and the corresponding recess is possible. In order to be able to form the largest possible projection and a correspondingly large recess in the case of elongate cross sections in order to increase the stability of the connection, it is favorable if at least one planar or substantially planar wall surface section is formed between the first and the second wall section. Thus, an available space can be used optimally to produce as large a contact surface as possible between the recess and the projection.

Especially with narrower in cross-section implant parts, it is advantageous if two substantially mutually opposite wall surface portions are formed and when a distance of the two wall surface portions in the direction of the second wall portion decreases. Thus, for example, a remaining, surrounding the recess wall of the first implant part can be formed with a constant thickness, whereby with constant stability of a connection of the at least two implant parts surface contact and thus a stability over known implant systems is increased.

According to a preferred embodiment of the invention, it may be provided that the at least one wall surface section extends at least in sections parallel or substantially parallel to an outer boundary surface of the first implant part. In this way, a cross-sectional area of the first implant part can be optimally utilized in order to form a recess with the largest possible cross section. In particular, the thickness of the remaining wall surrounding the recess can thus be kept constant, whereby a stability of the cone connection of the two implant parts is increased by the enlarged contact area between the recess and the projection. Preferably, an outer cross-sectional area of the first implant portion decreases from a proximal end toward a distal end. Such an implant part is, for example, outstandingly suitable for serving as a shaft of a hip joint endoprosthesis which can be inserted into a corresponding recess of a femur bone. Such a recess may, for example, form an optionally treated medullary cavity of the femur, which likewise decreases somewhat in cross-section starting from the hip joint.

An optimal adaptation of an implant to a recess into which it is to be inserted and whose width decreases in one direction can be achieved, in particular, by a width of a cross section of the first implant part at least in the region of the recess transversely to a connecting line between the first and decreases toward the second wall portion.

It is advantageous if curvatures of the first and / or second wall section curvatures of an outer boundary surface of the first implant part are at least partially similar or if the first or second wall section parallel or substantially parallel to the outer boundary surface. Thus, it is possible, independently of a cross section of the implant part, to form a maximally large recess in order to maximize a contact surface between the recess and the projection of the second implant part. The outer boundary surface of the first implant part is to be understood in particular also the complete outer surface of the first implant part, that is, the entire outwardly of the recess facing away surface of the first implant part, or even only a surface portion of this entire outer surface. Preferably, the first wall portion has a radius of curvature in a range of 4 mm to 10 mm.

It is favorable if the first wall section has a radius of curvature in a range of 5 mm to 8 mm. Such a curved wall section is suitable as a wall section for a multiplicity of applications, for example for hip joint endoprostheses.

Advantageously, the second wall portion has a radius of curvature in the range of 3 mm to 7 mm, which, however, is always smaller than a radius of curvature of the first wall portion.

It is advantageous if the second wall section has a radius of curvature in a range of 3 mm to 5 mm. This makes it possible to equip very slim and small implants with a stable cone connection.

In order to achieve the best possible fit between the projection and the recess, it is advantageous if an inner cross-sectional area of the recess decreases starting from a proximal end of the first implant part in the direction of a distal end of the first implant part. In particular, the desired conical connection can be achieved in a simple manner.

According to a preferred embodiment of the invention it can be provided that the projection has at least a first and a second outer conical cone wall portion and that a radius of curvature of the first cone wall portion is greater than a radius of curvature of the second cone wall portion. Preferably, the radii of curvature correspond the adjoining cone wall sections or wall sections of the second or first implant part.

In particular, in cases in which the first wall section merges directly into the second wall section, it is favorable if the first cone wall section merges directly into the second cone wall section. Thus, a contact area between the recess and the projection can be maximized.

In order to be able to form a projection with a high degree of symmetry, it is advantageous if the first cone wall section and the second cone wall section point away from one another or substantially away from one another.

In the case of implants whose first implant part has at least one flat or essentially flat wall surface section between the first and the second wall section, it is favorable if at least one planar or substantially planar cone wall surface section is formed between the first and second cone wall sections, because then one can Contact area between the projection and the recess to be maximized.

In order to maximize a contact surface between the projection and the recess, in particular in the case of implants which have substantially mutually opposite wall surface sections and in which a distance between the two wall surface sections decreases in the direction of the second wall section, it is advantageous if two cone wall surface sections pointing substantially away from one another are formed and when a distance of the two cone wall surface portions decreases in the direction of the second cone wall portion. Preferably, the first cone wall portion has a radius of curvature in a range of 4 mm to 10 mm. It is favorable if the radius of curvature of the cone wall section corresponds to the radius of curvature of the wall section against which it rests in the connection position.

Depending on the size of the implant, it may be favorable if the first cone wall section has a radius of curvature in a range of 5 mm to 8 mm.

Advantageously, the second cone wall portion has a radius of curvature in a range of 3 mm to 7 mm. Optimally, the radius of curvature of the second cone wall section corresponds to the radius of curvature of the wall section on which the second cone wall section abuts in the connection position.

In the case of particularly small implants, it can also be favorable if the second cone wall section has a radius of curvature in a range of 3 mm to 5 mm.

In order to achieve a clamping and / or self-locking connection between the projection and the recess, it is advantageous if a cross-section of the projection decreases in the direction of a distal end of the second implant part.

In principle, it would be conceivable to use the implant at various points in a human or animal body. According to a preferred embodiment of the invention, provision may in particular be made for the implant to be a hip joint endoprosthesis and for the first implant to be a hip joint endoprosthesis. plantatteil in the form of a shaft and that the second implant part are formed in the form of a modular neck of the hip joint endoprosthesis. This embodiment makes it possible to provide modular hip joint endoprostheses with an improved connection between the shaft and the neck part.

In order to minimize a number of connections of parts of the implant, it is advantageous if the modular neck part has a neck portion, to which the conically shaped projection is integrally formed on the distal side.

In order to connect the shaft of the hip joint endoprosthesis with a socket, it is advantageous if the modular neck part further carries a head part or can be connected to a head part of the hip joint endoprosthesis. The head part may in particular be of spherical design in order to be able to form a ball joint with a corresponding hollow spherical socket.

Advantageously, the hip joint endoprosthesis is a short stem prosthesis. This makes it possible in particular to anchor the shaft of the hip joint endoprosthesis without the use of bone cement in a femur bone.

In order to remove as little bone substance of the femur, it is advantageous if a shaft length of the shaft is a maximum of 15 cm.

The following description of a preferred embodiment of the invention serves in conjunction with the drawings for further explanation. It shows the

FIG. 1 is a perspective view of a portion of a modular hip joint endoprosthesis. FIG. Implants according to the invention can be used, for example, in spine surgery. Conceivable here would be a cone connection in particular between a voltage applied to a vertebral body portion of an intervertebral disc implant and a fixable thereto by means of the conical joint part. It would also be conceivable to connect modular knee prostheses, which consist of two or more parts, by means of a further developed cone connection according to the invention. However, implants according to the invention can also be used in the form of hip joint endoprostheses or parts thereof, which will be explained in detail with reference to the embodiment described in more detail below.

The FIGURE shows an implant according to the invention, provided overall with the reference numeral 10, which forms one or a part of a hip joint endoprosthesis. The implant 10 has a modular construction and comprises at least two implant parts, namely a first implant part in the form of a shaft 12 which can be inserted into a prepared medullary canal of a femur bone and a neck part 14 which can be connected to the shaft 12 and forms a second implant part it is preferably a modular implant, that is, it can be connected differently shaped neck parts with different shaped shanks. If a plurality of neck parts and / or shanks are provided, those elements which are provided to form a conical connection between the two implant parts are preferably identical, that is, there is preferably only one shape of a recess or only one shape of a projection corresponding to the recess.

For connection to the neck part 14, the shaft has at its proximal end a conical recess 16 which is open in the proximal direction and which has a first conical wall section 18 and a second conical wall section which is substantially opposite the first wall section 18. section 20 has. Although it would be conceivable that the two wall sections 18 and 20 merge directly into each other, but in the embodiment shown in the figure between the first wall portion 18 and the second wall portion 20 two substantially opposite planar or substantially planar wall surface portions 22 and 24 are formed that run substantially parallel to an outer boundary surface 26 of the shaft 12.

The shaft 12 is shaped such that an outer cross-sectional area thereof decreases from its proximal end, in which the recess 16 is formed, towards a distal end 28. Further, a width of a cross section of the shaft 12 in the region of the recess 16 decreases transversely to a connecting line 30 between the first wall section 18 and the second wall section 20 in the direction of the latter. Consequently, a distance of the two wall surface portions 22 and 24 in the direction of the second wall portion 20 decreases.

Curvature radii of the two wall sections 18 and 20 are not identical. Curvature radii of the first wall portion 18 may be in particular in a range of 4 mm to 10 mm. In the embodiment shown in the figure, the radius of curvature of the first wall portion is 5.5 mm. The radius of curvature of the second wall portion 22 is less than the radius of curvature of the first wall portion 18 and may be in a range of 3 mm to 7 mm. In the embodiment shown in the figure, the radius of curvature of the second wall portion is 5 mm.

The recess 16 makes optimal use of a cross section of a shaft 12, because in the region of the widening cross section of the shaft 12, the First wall portion 18 have a maximum large radius of curvature, which is greater than the radius of curvature of the second wall portion 20th

The neck portion 14 has a projection 32 substantially corresponding to the recess 16 in the form of a conical pin, which is also referred to as an oval cone. The projection comprises a first cone wall portion 34 and a second cone wall portion 36 facing away therefrom. Although the first and second cone wall portions 34 and 36 can merge directly with each other, in the embodiment shown in the figure, two planar portions 34 and 36 between the two cone wall portions or substantially flat cone wall surface portions 38 and 40 are formed, which abut against the wall surface portions 22 and 24 in a connecting position in which the projection 32 is inserted into the recess 16. Curvature radii of the cone wall sections 34 and 36 substantially correspond to those of the wall sections 18 and 20 of the recess 16. The radius of curvature of the first cone wall section 34 is greater than the radius of curvature of the second cone wall section 36, which directly results in the two substantially facing away from each other Konuswandflächenabschnitte 38 and 40 toward each other in the direction of the second cone wall portion 36, that is, a distance of the two cone wall surface portions 38 and 40 decreases in the direction of the second cone wall portion 36 from.

Preferably, the angles of inclination of the wall sections 18 and 20 are somewhat shallower relative to a longitudinal axis defined by the recess 16 than the angles of inclination of the cone wall sections 34 and 36 with respect to a longitudinal axis defined by the projection 32. Thus, an optimal contact of the projection 32 on inner surfaces of the recess 16 in the region of an upper edge of the recess 16 can be achieved. Alternatively, it would also be conceivable to incline the wall sections 18 and 20 identically to Forming angles of the cone wall sections 34 and 36, whereby a large-area contact between the voltage applied to the wall portion 18 cone wall portion 34 and the voltage applied to the wall portion 20 cone wall portion 36 can be reached.

The neck portion 14 is integrally formed as a whole, that is, the projection 32 is integrally formed on a neck portion 42, which in turn carries a frustoconical, rotationally symmetric cone 44 for connection to a condyle, not shown. If a whole set of neck parts is provided, these differ essentially in their neck sections, that is to say their position and / or angle relative to the projection 32 and their length, ie their extent between the cone 44 and the projection 32.

To connect the neck portion 14 with a condyle, not shown, of the implant 10, a conical, corresponding to the cone 44 recess is provided on the condyle.

Due to the larger radius of curvature in the region of the first wall section 18 and the first cone wall section 34 in the highly loaded lateral region of the cone connection, the special configuration of the cone connection with the recess 16 and the projection 32 allows a larger contact surface and thus less abrasion overall. A load of the cone connection of the implant 10 is usually in the form of a spatial alternating load, that is, the direction of the force action line is time-dependent. Consequently, the contact area within the cone connection is not consistent. Therefore, a round contact surface formed by wall sections 18 and 20 and to these corresponding cone wall sections 34 and 36, respectively as large a curvature as possible an optimal connection geometry with the highest possible congruence under changing load.

Claims

claims

1. implant (10) comprising at least a first implant part (12) and a first implant part (12) by means of a conical connection (16, 32) connectable second implant part (14), wherein the first implant part (12) has a conically shaped recess ( 16) and the second implant part (14) has a conically shaped projection (32) corresponding to or substantially corresponding to the recess (16) and can be inserted into it and clamped or press-fitted in a connection position, characterized in that the recess (16 ) has at least a first and a second conical wall section (18, 20) and that a radius of curvature of the first wall section (18) is greater than a radius of curvature of the second wall section (20).

2. Implant according to claim 1, characterized in that the first wall section (18) passes directly into the second wall section (20).

3. Implant according to one of the preceding claims, characterized in that the first wall portion (18) opposite to the second wall portion (20) or substantially opposite.

4. Implant according to one of the preceding claims, characterized in that between the first and the second wall portion (18, 20) at least one flat or substantially planar wall surface portion (22, 24) is formed.

5. Implant according to claim 4, characterized in that two substantially mutually opposite wall surface portions (22, 24) are formed and that a distance of the two wall surface portions (22, 24) in the direction of the second wall portion (20) decreases towards.

6. Implant according to one of claims 4 or 5, characterized in that the at least one wall surface portion (22, 24) at least partially parallel or substantially parallel to an outer boundary surface (26) of the first implant part (12).

7. Implant according to one of the preceding claims, characterized in that an outer cross-sectional area of the first implant part (12) decreases starting from a proximal end in the direction of a distal end (28).

8. Implant according to one of the preceding claims, characterized in that a width of a cross section of the first implant part (12) at least in the region of the recess (16) transversely to a connecting line (30) between the first and the second wall portion (18, 20) decreases.

9. Implant according to one of the preceding claims, characterized in that curvatures of the first and / or second wall portion (18, 20) curvatures of an outer boundary surface (26) of the first implant part (12) are at least partially similar or that the first or second wall portion (18, 20) run parallel or substantially parallel to the outer boundary surface (26).

10. Implant according to one of the preceding claims, characterized in that the first wall portion (18) has a radius of curvature in a range of 4 mm to 10 mm.

11. An implant according to claim 10, characterized in that the first wall portion (18) has a radius of curvature in a range of 5 mm to 8 mm.

12. Implant according to one of the preceding claims, characterized in that the second wall portion (20) has a radius of curvature in a range of 3 mm to 7 mm.

13. Implant according to claim 12, characterized in that the second wall portion (20) has a radius of curvature in a range of 3 mm to 5 mm.

14. Implant according to one of the preceding claims, characterized in that an inner cross-sectional area of the recess (16) decreases starting from a proximal end of the first implant part (12) towards a distal end (28) of the first implant part (12).

15. Device according to one of the preceding claims, characterized in that the projection (32) has at least a first and a second outer conical cone wall portion (34, 36) and that a radius of curvature of the first cone wall portion (34) greater than a radius of curvature of the second cone wall portion (36) is.

16. Implant according to claim 15, characterized in that the first cone wall section (34) merges directly into the second cone wall section (36).

17. Implant according to one of claims 15 or 16, characterized in that the first cone wall portion (34) and the second cone wall portion (36) away from each other or substantially away from each other.

18. Implant according to one of claims 15 to 17, characterized in that between the first and the second cone wall portion (34, 36) at least a flat or substantially planar Konuswandflä- chenabschnitt (38, 40) is formed.

19. An implant according to claim 18, characterized in that two mutually substantially facing away Konuswandflächenab- sections (38, 40) are formed and that a distance between the two Koususwandflächenabschnitte (38, 40) in the direction of the second cone wall portion (40 ) decreases.

20. Implant according to one of claims 15 to 19, characterized in that the first cone wall portion (34) has a radius of curvature in a range of 4 mm to 10 mm.

21. An implant according to claim 20, characterized in that the first cone wall portion (34) has a radius of curvature in a range of 5 mm to 8 mm.

22. Implant according to one of claims 15 to 21, characterized in that the second cone wall portion (36) has a radius of curvature in a range of 3 mm to 7 mm.

23. Implant according to claim 22, characterized in that the second cone wall portion (36) has a radius of curvature in a range of 3 mm to 5 mm.

24. Implant according to one of the preceding claims, characterized in that a cross section of the projection (32) decreases in the direction of a distal end of the second implant part (14).

25. Implant according to one of the preceding claims, characterized in that the implant (10) is a hip joint endoprosthesis and that the first implant part (12) in the form of a shaft (12) and that the second implant part (14) in the form of a modular neck part ( 14) of the hip joint endoprosthesis are formed.

26. An implant according to claim 25, characterized in that the modular neck portion (14) has a neck portion (42) to which the conically shaped projection (32) is integrally formed on the distal side.

27. Implant according to one of claims 25 or 26, characterized in that the modular neck portion (14) further carries a head portion or is connectable to a head portion of the hip joint endoprosthesis.

28. Implant according to one of claims 25 to 27, characterized in that the hip joint endoprosthesis is a short stem prosthesis.

29. Implant according to one of claims 25 to 28, characterized in that a shaft length of the shank (14) is at most 15 cm.