ZA200602369B - Dynamic damping element for two bones - Google Patents

Description

2083/PCT 29.9.2003 rh gl

English translation of the specification of the International Patent Application No.

PCT/CHO03/00649 "Dynamic damping element for two bodies” in the name of

Mathys Medizinaltechnik AG

Dynamic damping element for two bodies

The invention concerns a damping element according to the preamble of patent claim 1.

From FR 2 812 186 Pasquet a damping element of the generic type is already known, that can be used within a fixing device for the spinal column, for example as a connecting element between two adjacent pedicle screws. This known damping element comprises essentially two axially external longitudinal connecting elements and a part provided between them, that is made from a material having a greater elastic deformability than the external connecting elements. A disadvantage of this known damping element is that the spring characteristics of the middle, elastic part is determined by the geometry and the choice of material.

This is where the invention wants to provide remedy. The object of the invention is to produce a damping element with a progressive spring characteristics, the progression of which can be selected.

This objective is achieved by the invention by a damping element having the features of claim 1.

Further advantageous developments of the invention are characterised in the dependent claims.

The advantages achieved by the invention are essentially that by virtue of the damping element according to the invention = a progressive spring characteristics can be set, that assures an adequately great elastic flexibility in the case of small spring travels. Due to this an adequate freedom of movement of the spinal column is possible in this region:

> In the case of an adjustable spring travel a greater resistance occurs, so that an overload of the posterior elements can be avoided: and ° No overloads on the bodies of the vertebra or on the intervertebral disk, lying in the intervertebral space, will occur even in the case of impact loads.

The dimension X is preferably between 0-2 mm. By virtue of this the spring travel of the spring element can be set with the spring characteristics of f;. As soon as the spring element is axially compressed by the dimension X, the front end of the clamping sleeve, introduced into the hollow space of the spring element, abuts against the face of the hollow space, so that during a further axial compression of the spring element the end wall in the hollow space of the spring element will be deformed and thus a greater spring characteristics f, will prevail.

The field element is made preferably from an elastomer, whereas the clamping sleeve is manufactured preferably from a metallic material, particularly from titanium.

In another embodiment the front end of the clamping sleeve has a convex construction. This spring characteristics f, can be influenced by the shape of the convex face on the front end of the clamping sleeve, so that, for example, by virtue of a flat convex face a stronger progression of the spring characteristics f, can be achieved than would be the case with a convex face having a greater curvature.

In yet another embodiment the connecting parts are joined with the spring element rotatably and axially form-locked. For this purpose the connecting parts have preferably barbs on their faces, directed towards the spring element, and said barbs could be cast into the ends of the spring element.

In a further embodiment the connecting part comprises externally a rod that js coaxial with the longitudinal axis, by virtue of which the damping element can be joined, for example, with a bone anchoring element.

In yet another further embodiment the second connecting part is constructed as a bush with a central bore that is coaxial with the longitudinal axis, while the clamping sleeve can pass through the central bore, at least partially. The locking of a rod-shaped longitudinal support in the clamping sleeve is carried out preferably by wedging an internal taper provided in the central bore of the bush (21) into a complementary external taper on the clamping sleeve. For the purpose of accepting a rod-shaped longitudinal support of an osteosynthetic stabilising device, the clamping sleeve has a coaxial blind hole open at the rear end.

In another embodiment the radial elastic deformability of the clamping sleeve is achieved by at least one slot radially penetrating the wall of the clamping sleeve.

The compression of the clamping sleeve is carried out by a thread provided on the bush, over which a locking means, preferably constructed as a nut, can be screwed.

The invention and developments of the invention are explained in the following in detail based on the partly schematic illustrations of several embodiments, They show in:

Fig.1 - an exploded illustration of an embodiment of the damping element according to the invention, and

Fig.2 - a longitudinal section through the embodiment of the damping element according to the invention illustrated in Fig.1, in the assembled state.

In Figs.1 and 2 an embodiment is illustrated, that comprises a damping element 1 with a longitudinal axis 3, an external longitudinal connecting part 4, an axially opposed external hollow body-shaped connecting part 5 and an elastic means 2 provided coaxially between them.

The hollow body-shaped connecting part 5 is constructed as a hollow cylindrical bush 21 and has an outside diameter corresponding to that of the elastic middle part 2. The longitudinal connecting part 4 comprises axially externally a cylindrical rod 12 and a flange 11 bordering the elastic middle part 2, the outside diameter of the flange corresponding approximately to that of the elastic middie part 2. The hollow body-shaped connecting part 5 has a first face 7 which is directed towards the elastic middle part 2 and is perpendicular to the longitudinal axis 3. Similarly to that, the flange 11 has a second face 6 which is directed towards the elastic middle part 2 and is perpendicular to the longitudinal axis 3.

The faces 6, 7 on the connecting parts 4, 5, directed towards the elastic middle part 2, are provided with barbs 8, which are arranged circumferentially on a circle concentrically with the longitudinal axis 3. The barbs 8 are cast during the manufacture of the longitudinal support 1 into the external ends 9, 10 of the elastic middle part 2, so that an axial and rotational form-locking is produced between the elastic middle part 2 and the axially external connecting parts 4, 5.

The elastic middle part 2 is in this case cylindrical and comprises a spring element 20 that is coaxial with the longitudinal axis 1 with an equally coaxial hollow space 13 and a clamping sleeve 15 coaxially arranged in the hollow space 13. The hollow space 13 is axially open towards the hollow body-shaped connecting part 5 and enclosed towards the longitudinal connecting part 4 with an end wall 14 that is perpendicular to the longitudinal axis 3.

The clamping sleeve 15 can be axially introduced into the central bore 16 in the hollow body-shaped connecting part 5 as well as the hollow space 13. In the embodiment illustrated here the clamping sleeve 15 has at its front end a convex face 18 directed towards the end wall 14 of the hollow space 13, the convex face being in the non-deformed state of the elastic middle part 2 at an axial distance of

X from the end wall 14 of the hollow space 13 (Fig.2). The result of this is that under an axial load on the elastic middle part 2, this will be first deformed with the spring characteristics f; of the spring element 20. As soon as the spring element 20 is compressed axially by the dimension X, the apex of the convex face 18 at the front end 17 of the clamping sleeve 15 abuts against the end wall 14 of the hollow space 13, so that during a further axial compression of the elastic middle part 2 the end wall 14 will be deformed in the hollow space 13 of the spring element 20, and consequently a higher spring characteristics f, will prevail. This spring characteristics f, can be influenced by the shape of the convex face 18 at the front end 17 of the clamping sleeve 15, so that by virtue of a flat convex face 18 a stronger progression of the spring characteristics f, can be achieved than would be the case if the a convex face 18 would have a greater curvature.

Furthermore. by virtue of the axially variable position of the clamping sleeve 15 in the hollow space 20 relative to the spring element 20, the dimension X and consequently the transition of the spring characteristics from f; of the spring 5 element 20 to a higher spring characteristics f, of the spring element 20, abutting against the front end 17 of the clamping sleeve 18, can be adjusted.

The hollow cylindrical connecting part 5 is made in this case from two parts and comprises a bush 21 that on its external end 23 has a thread 22. The bush 21 has a central bore 16 that is coaxial with the longitudinal axis 3, while the central bore 16 expands into an internal taper 25 towards the external end 23 of the bush 21. The diameter of the central bore 16 is so dimensioned, that the clamping sleeve 15 can be introduced into the central bore 16. On its rear end 24 the clamping sieeve 15 has an external taper 26, that can be wedged into the internal taper 25 in the central bore 16 of the bush 21. The clamping sleeve 15 has a coaxial blind hole 19 that is open at the rear end 24, into which a rod-shaped longitudinal support (not illustrated) can be introduced from the rear end 24.

Furthermore, the rear end 24 of the clamping sleeve 15 has at least one slot 27 that radially penetrates the wall of the inner spring element 15, so that when the external taper 26 is pressed into the internal taper 25 the rear end 24 of the clamping sleeve 15 is radially compressed and a rod-shaped longitudinal support, introduced into the blind hole 19, can be secured. The axial displacement of the clamping sleeve 15 relative to the spring element 20 is carried out by locking means 20, which is constructed in this case as a nut 28 that can be screwed onto the bush 21 via the thread 22. The nut 28 has a coaxial bore 29 with an inside thread 30 and an axially external constriction 31. When the nut 28 is screwed on the external end 23 of the bush 21 via the thread 22, the rear end 24 of the clamping sleeve 15 will abut against the shoulder 32 formed by the constriction 31, so that during further tightening of the nut 28 the Clamping sleeve 15 js radially compressed.

Claims (19)

W02005/030068 : PCT/CH2003/000639 Patent claims

1. A damping element for the dynamic stabilisation of two bones, comprising A) a spring element that is coaxial with the longitudinal axis with a first end intersecting the longitudinal axis, a second end intersecting the longitudinal axis and a coaxial hollow space, that is open on the first end and enclosed on the second end by a wall extending transversely to the longitudinal axis, B) on each of the two ends a coaxial connecting part is provided, that is suitable for fixing the damping element on both sides within an osteosynthetic stabilising device, characterised in that C) a clamping sleeve penetrating coaxially the hollow space at least partially, the clamping sleeve having a front end directed towards the second end of the external spring element , while D) there is an axial dimension of X > 0 between the front end of the clamping sleeve and the end wall of the hollow space

2. A damping element according to claim 1, characterised in that the dimension X is between 0 mm and 2 mm.

3. A damping element according to claim 1, characterised in that the field element is made from an elastomer.

4 A damping element according to anyone of claims 1 to 3, characterised in that the clamping sleeve is made from a metallic material.

5. A damping element according to anyone of claims 1 to 4, characterised in that the front end of the clamping sleeve has a convex construction. AMENDED SHEET

W02005/030068 PCT/CH2003/000639

6. A damping element according to anyone of claims 1 to 5, characterised in that the connecting parts are joined with the external spring element rotatably and axially form-locked.

7. A damping element according to claim 6, characterised in that the connecting parts have faces directed against the spring element, the faces fitted with barbs .

8. A damping element according to claim 7, characterised in that the barbs are cast into the ends of the spring element .

9. A damping element according to anyone of claims 1 to 8, characterised in that a connecting part comprises externally a rod that is coaxial with the longitudinal axis

10. A damping element according to anyone of claims 1 to 9, characterised in that the second connecting part is constructed as a bush with a central bore that is coaxial with the longitudinal axis, while the internal spring element can pass : through the central bore , at least partially.

11. A damping element according to claim 10, characterised in that on the external end of the bush the central bore comprises an internal taper that coaxially tapers from the outside.

12. A damping element according to claim 11, characterised in that the clamping sleeve comprises an external rear end with an external taper that is complementary to the internal taper

13. A damping element according to claim 12, characterised in that the clamping sleeve has a coaxial blind hole open at the rear end to accept a rod-shaped part of an osteosynthetic stabilising device. AMENDED SHEET

WO02005/030068 PCT/CH2003/000639

14. A damping element according to claim 12 or 13, characterised in that the clamping sleeve has at least one slot at the rear end which radially penetrates the wall of the clamping sleeve . i

15. A damping element according to anyone of the claims 10 to 14, characterised in that bush comprises a thread at its externalend.

16. A damping element according to claim 15, characterised in that it comprises a fastening means apt to radially compress the rear end of the clamping sleeve .

17. A damping element according to claim 16, characterised in that the fastening means comprise a nut being screwable on the thread at the bush.

18. Damping element for the dynamic stabilisation of two bones substantially as herein described and as illustrated in Figures 1 and 2.

19. A damping element according to any proceeding claim, wherein the two bones are two adjacent bodies of the vertebra. i AMENDED SHEET