EP1848379A1

EP1848379A1 - Intervertebral implant

Info

Publication number: EP1848379A1
Application number: EP05700371A
Authority: EP
Inventors: Beat Lechmann; Roger BÜRKI; Mario Gago; Robert Frigg; Michael H. Mayer
Original assignee: Synthes GmbH
Current assignee: Synthes GmbH
Priority date: 2005-02-16
Filing date: 2005-02-16
Publication date: 2007-10-31
Also published as: KR20070118590A; NZ556745A; TW200640434A; KR100953148B1; CN101119687A; WO2006086895A1; US20080033554A1; US8702797B2; CN101119687B; CA2598136C; CA2598136A1; AU2005327500A1; JP2008529685A; BRPI0519972A2

Abstract

The inventive intervertebral implant (1), in particular an artificial intervertebral disc comprises a central axis (2), a top part (3) and a lower part (4), wherein A) the top part (3) is provided with a top apposition surface (5) which rests on a base plate of a superimposed vertebral body, B) the lower part (4) is provided with a lower apposition surface (6) for resting on the covering plate of an underneath vertebral body, C) one part (3, 4) comprises a convex joint element (12) provided with a convex sliding surface (11) and the other part (3, 4) comprises a joint shell (13) provided with a complementary concave surface, D) the convex joint element (12) and the convex joint shell (13) form a joint (9) by means of which the two parts (3, 4) are rotatable with respect to each other around at least one axis of rotation and E) the intervertebral implant (1) is permeable to x-rays.

Description

Intervertebral implant

The invention relates to an intervertebral implant, in particular artificial intervertebral disc, according to the preamble of patent claim 1.

After removal of a damaged, natural disc or a damaged nucleus pulposus of an intervertebral disc today implants or prostheses are introduced into the intervertebral space of two adjacent vertebral bodies. The goal of implanting such implants is to restore as natural a state as possible, i. in particular, restore the original disc height and thus the original distance between the two adjacent vertebral bodies. Furthermore, movements of the adjacent vertebral bodies relative to each other should be possible in their natural way as far as possible without hindrance. For this purpose, the preservation of the possibilities of movement in a forward / backward inclination, i. Flexion and extension of the vertebral bodies as well as in a lateral flexion of the vertebral bodies within the natural limits essential. The natural ligaments and muscles along the spine are left essentially intact so that they further stabilize the movements of a mechanical disc replacement.

Such an intervertebral implant is known from DE 203 20 454 MEISEL. This known implant comprises two covering plates resting against the bone and a joint arranged between the cover plates. This joint consists essentially of a dome-shaped, first joint part and a complementary joint shell as a second joint part, so that the cover plates are pivotable relative to each other polyaxially. A disadvantage of this known intervertebral implant is that it is radiopaque and thus no longer allows observation of the adjacent vertebral bodies after implantation.

The invention aims to remedy this situation. The invention has for its object to provide an intervertebral implant, which is transparent to both Magnetic Resonance Imaging (MRI) and X-rays and thus allows postoperative X-ray observation while having high MRI compatibility. The invention solves this problem with an intervertebral implant, in particular an artificial intervertebral disc, which has the features of claim 1.

The advantages achieved by the invention are essentially to be seen in the fact that thanks to the intervertebral implant according to the invention, the MRI compatibility is increased and the observation by means of X-rays is made possible.

Further advantageous embodiments of the invention are characterized in the dependent claims.

In a preferred embodiment, the upper part and the lower part are made of a first radiolucent material while the convex hinge part and the joint shell are made of a different second, also radiolucent material. The advantages achieved thereby are mainly to be seen in that for the joint parts materials with particularly favorable sliding and Abriebeigenschaften can be used, while the outer parts of materials which are suitable for contact with bone, can be made.

In another embodiment, the individual parts of the intervertebral implant are made of the same material. The advantage of this embodiment is that the bone contact elements can also be made of ceramic materials.

In yet another embodiment, the radiopaque material for the upper part and the lower part is selected from the group of polyaryletherketones, polyetheretherketones, ultra-high molecular weight polyethylenes or polysulfones.

In a further embodiment, the convex hinge part and the joint shell are made of a ceramic material. The advantages of this embodiment are essentially to be seen in the fact that the hinge parts made of ceramic materials similar to the cobalt-chromium-molybdenum alloys have a low abrasion during articulation movements, but are transparent to MRI and X-rays.

In yet another embodiment, the upper and lower apposition surfaces have a different shape from each other. The advantages that can be achieved thereby lie in particular in the production of a shape of the implant which is favorable with respect to the anatomy of the end plates. The intervertebral implants with different contact surfaces are particularly suitable for the cervical spine.

In another embodiment, the upper and lower apposition surfaces have the same shape. The advantages here are that intervertebral implants with symmetrical contact surfaces in the sagittal profile are particularly suitable for the lumbar spine.

In yet another embodiment, the convex hinge part is fixedly connected to one of the two parts and the joint shell fixed to the other of the two parts. This provides the advantage that the implant can be assembled prior to implantation, so that a simpler insertion into the intervertebral space is achievable.

In another embodiment, the upper part and the lower part are provided with macroscopic structures on their apposition surfaces, so that migration movements of the implanted intervertebral implant can be prevented.

In yet another embodiment, connecting means are provided whereby the upper part and the lower part are held together without impairing the pivotability of the joint. The advantage of this connection means is that the intervertebral implant is held together in situ and no parts can be lost.

In another embodiment, the connecting means at each articulation of the joint an axial play X> 0 between the convex hinge part and the Joint shell, so that can build up a lubricating film of the body's own fluids between the sliding surfaces.

In yet another embodiment, the clearance X is at least 0.005 mm, preferably at least 0.05 mm.

In a further embodiment, the game X is a maximum of 0.5 mm, preferably a maximum of 0.6 mm.

In yet another embodiment, the connecting means comprise an anchoring element which can be connected to one of the two parts and is loosely mounted in the other of the two parts.

In another embodiment, the convex hinge part has a cavity which is open on the central axis lying apex of the convex hinge part and wherein the anchoring element is axially movable so far that it comes after overcoming the game X axially against the cavity wall.

In yet another embodiment, all components of the intervertebral implant consist of a radiolucent material.

The invention and further developments of the invention are explained in more detail below with reference to the partially schematic representations of an embodiment.

Show it:

1 shows a lateral view of an embodiment of the intervertebral implant according to the invention;

FIG. 2 shows a section through the embodiment of the intervertebral implant according to the invention shown in FIG. 1; FIG. 3 shows a perspective view of a further embodiment of the intervertebral implant according to the invention; and

4 shows a longitudinal section through the embodiment of the inventive intervertebral implant shown in FIG.

The embodiment of the inventive intervertebral implant 1 illustrated in FIGS. 1 and 2 essentially comprises an upper part 3 with an upper apposition surface 5 intersecting the central axis 2 for engagement with the base plate of the above adjacent vertebral body, a lower part 4 with a central axis 2 cutting, lower apposition surface 7 for abutment with the cover plate of the below adjacent vertebral body and a joint 9 arranged between the two parts 3, 4 for the articulated connection of the two parts 3, 4. The joint 9 is formed in two parts, wherein the convex joint part 12 is designed spherical, such that the central axis 2 intersects the apex perpendicular. At the rear end 16, the convex joint part 12 is tapered in its orthogonal to the central axis 2 cross-section and pressed into a complementary to the central axis 2 coaxial recess 17 in the lower part 4 or poured. Similarly, the convex joint part 12 complementary configured joint shell 13 is tapered at its rear end 21 in its orthogonal to the central axis 2 cross-section and pressed into a complementary recess 22 in the upper part 3. The upper and the lower part 3, 4 and the joint shell 13 and the convex joint part 12 are formed as separate workpieces, so that the upper and the lower part 3, 4 are made of PEEK, for example, while the convex joint part 12 and the joint shell 13 for example, can be made of a ceramic material. The convex sliding surface 11 on the convex joint part 12 and the concave sliding surface 10 on the joint shell 13 have the same radius, which allows sliding of the convex joint part 12 and the joint shell 13 relative to each other.

Furthermore, the upper and lower Appositionsfläche 5, 7 have a different shape. The lower Appositionsfläche 7 is concave, while the upper Appositionsfläche 5 is convex. The embodiment shown in FIGS. 3 and 4 differs from the embodiment shown in FIGS. 1 and 2, first, in that it has two convex apposition surfaces 5, 7. The two parts 3, 4 each have a ventral side surface 31, 41, one dorsal side surface 32, 42 and two lateral side surfaces 33, 34, 43, 44. Secondly, the hinge 9 is held together axially together with the upper and lower parts 3, 4 by means of connecting means 20 (Figure 4). The connecting means 20 comprise an anchoring element 15 which is arranged coaxially to the central axis 2 and comprises a pin 23 which penetrates with its rear end 24, the joint shell 13 at the apex and is secured to the upper part 3. Furthermore, the anchoring element 15 comprises a larger diameter a having circular disk-shaped extension 25, which is arranged at the front end 26 of the pin 23. The convex joint part 12 has an opening 28 which is coaxial with the central axis 2 and which opens into a cylindrical cavity 29, which has a larger diameter, inside the convex joint part 12. The geometry of the anchoring element 15 and the opening 28 and the cavity 29 is selected such that the pin 23 in the opening 28 and the extension 25 in the cavity 29 are arranged movable. The diameter d of the opening 28 is smaller than the diameter a of the circular disk-shaped enlargement 25, while the diameter D of the cavity 29 is greater than the diameter a, so that the convex hinge part 12 and the joint shell 13 and thus the two parts 3; 4 are held together axially, without the movement of the joint 9 is hindered. The mobility of the pin 23 in the opening 28 and the extension 25 in the cavity 29 allow a polyaxial pivoting of the two parts 3, 4 relative to each other. The length of the pin 23 is dimensioned so that the extension 25 comes at the front end 26 of the pin 16 at each articulation of the joint 9 only after overcoming the game X at the transition between the opening 28 and the cavity 29 to the plant.

Claims

claims

1. intervertebral implant (1), in particular artificial disc, with a central axis (2), an upper part (3) and a lower part (4), wherein

A) the upper part (3) has an upper Appositionsfläche (5) which is suitable for bearing against the base plate of an overlying vertebral body;

B) the lower part (4) has a lower Appositionsfläche (6) which is suitable for bearing against the cover plate of an underlying vertebral body;

C) one of the two parts (3; 4) comprises a convex joint part (12) with a convex sliding surface (11) and the other of the two parts (3; 4) a joint shell (13) with a complementary concave sliding surface (10);

D) the convex joint part (12) and the joint shell (13) form a joint (9), by means of which the two parts (3; 4) are rotatable relative to each other about at least one axis of rotation, characterized in that

E) the intervertebral implant (1) is radiolucent.

2. intervertebral implant (1) according to claim 1, characterized in that the upper part (3) and the lower part (4) are made of a first radiolucent material and the convex hinge part (12) and the joint shell (13) of a different second, also radiolucent material are made.

3. intervertebral implant (1) according to claim 1, characterized in that its individual parts are made of the same material.

4. intervertebral implant (1) according to one of claims 1 to 3, characterized in that the X-ray permeable material for the upper part (3) and the lower part (4) from the group of polyaryletherketones, polyetheretherketones, ultra high molecular weight polyethylenes or polysulfones is selected.

5. intervertebral implant (1) according to one of claims 1 to 4, characterized in that the convex hinge part (12) and the joint shell (13) are made of a ceramic material.

6. intervertebral implant (1) according to one of claims 1 to 5, characterized in that the upper and the lower Appositionsfläche (5; 7) have a mutually different shape.

7. intervertebral implant (1) according to one of claims 1 to 5, characterized in that the upper and lower Appositionsfläche (5; 7) have the same shape.

8. intervertebral implant (1) according to one of claims 1 to 7, characterized in that the convex hinge part (12) fixed to one of the two parts (3; 4) and the joint shell (13) fixed to the other of the two parts (3 ; 4) are connected.

9. intervertebral implant (1) according to one of claims 1 to 8, characterized in that the upper part (3) and the lower part (4) at their Appositionsflächen (5; 7) are provided with macroscopic structures (18).

10. intervertebral implant (1) according to one of claims 1 to 9, characterized in that connecting means (20) are provided, whereby the upper part (3) and the lower part (4) are held together without the pivotability of the joint (9 ) is impaired.

11. intervertebral implant (1) according to claim 10, characterized in that the connecting means (20) at each articulation of the joint (9) allow an axial clearance X> 0 between the convex hinge part (12) and the joint shell (13).

12. intervertebral implant (1) according to claim 11, characterized in that the game X is at least 0.005 mm, preferably at least 0.05 mm.

13. intervertebral implant (1) according to claim 11 or 12, characterized in that the game X is at most 0.5 mm, preferably at most 0.6 mm.

14. An intervertebral implant (1) according to any one of claims 10 to 13, characterized in that the connecting means (20) connectable to one of the two parts (3; 4) and in the other of the two parts (3; 4) loosely mounted anchoring element (20). 15).

15. Intervertebral implant (1) according to claim 14, characterized in that the convex joint part (12) has a cavity (29) which is open on the central axis (2) lying apex of the convex joint part (12) and wherein the anchoring element ( 15) is axially movable so far that it comes after overcoming the game X axially to the cavity wall to the plant.

16. intervertebral implant (1) according to one of claims 1 to 15, characterized in that all components consist of a radiolucent material.