SCREW

Abstract

A screw includes a head part, a threaded part and a flexible connector between the head part and the threaded part for transmitting a torsional force between the head part and the threaded part, and to allow two bending movements between the head part and the threaded part in the opposite direction in the longitudinal axis of the screw, wherein the head part and the threaded part in each case have a longitudinal axis, which can be arranged offset in parallel to one another, and wherein the screw has an -module of between 20,000 and 100,000 N/mm.sup.2 against a rotation in the case of an arrangement of the head part and the threaded part on a longitudinal axis.

Claims

1. A screw (1, 30) comprising a head part (2, 31), a threaded part (3, 32) and a flexible connector (4, 34) between head part (2, 31) and threaded part (3, 32) for transmitting a torsional force between head part (2, 31) and threaded part (3, 32), and to allow two bending movements between head part (2, 31) and threaded part (3, 32) in the opposite direction in the longitudinal axis of the screw, wherein head part (2, 31) and threaded part (3, 32) in each case have a longitudinal axis, which can be arranged offset in parallel to one another, and wherein the screw has an -module of between 20,000 and 100,000 N/mm.sup.2 against a rotation in the case of an arrangement of head part (2, 31) and threaded part (3, 32) on a longitudinal axis.

2. The screw according to claim 1, wherein the screw has an offset of at least 0.3 mm per 6 mm length of the flexible connector between the longitudinal axis of the head part and a longitudinal axis of the threaded part, which is parallel thereto, in the area of the flexible connector.

3. The screw according to claim 1, wherein the flexible connector (4, 33) has a plurality of cooperating joint elements (8-11, 37-40) one behind the other in the axial direction between head part (2, 31) and threaded part (3, 32).

4. The screw according to claim 1, wherein the flexible connector (4, 33, 70) as coupling has a first coupling element (5, 34, 50, 60) with a plug-in connector (6, 36) for transmitting torsional forces, and a second coupling element (7, 41) for transmitting torsional forces.

5. The screw according to claim 4, wherein the first (5) and the second coupling element (7, 41) are arranged concentrically to one another.

6. The screw according to claim 4, wherein the first coupling element (5, 34) is arranged around the second coupling element (7, 41).

7. The screw according to claim 4, wherein the first coupling element (5, 34) has a groove and tongue joint (15, 43) as positive connection (14, 42).

8. The screw according to claim 4, wherein the first coupling element (5) has a dovetail joint (18) as positive connection (14).

9. The screw according to claim 4, wherein the first coupling element (5, 34) has a plurality of annular joint elements (8-11, 37-40).

10. The screw according to claim 9, wherein the annular joint elements (8-11, 37-40) are threaded onto the second coupling element (7, 41).

11. The screw according to claim 4, wherein the second coupling element (7, 41) is only a single element comprising only one central longitudinal axis of extension.

12. The screw according to claim 4, wherein the second coupling element (7, 41) is a rope, a cord or a chain.

13. The screw according to claim 4, wherein at the diameter of the second coupling element is between 0.5 and 5 mm.

14. The screw according to claim 4, wherein at least a first end (20) of the second coupling element (7) is arranged in the head part (2).

15. The screw according to claim 4, wherein at least a second end (21) of the second coupling element (7) is arranged in the threaded part (3).

16. The screw according to claim 4, wherein the maximum diameter (22) of the coupling elements (8-11) is not larger than and preferably even smaller than the maximum outer diameter (23) of the threaded part (3).

17. The screw according to claim 4, wherein the diameter (22) of the coupling elements (8-11) is between 2.0 mm and 8.5 mm.

18. The screw according to claim 1, wherein the screw (1, 30) is a bone screw.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other objects and features of the invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the invention.

[0025] In the drawings,

[0026] FIG. 1 shows a view of a screw comprising dovetail toothing,

[0027] FIG. 2 shows a section through the screw shown in FIG. 1,

[0028] FIG. 3 shows a perspective view of the screw shown in FIG. 1,

[0029] FIGS. 4-7 show different views of a coupling element of the screw shown in FIG. 1,

[0030] FIG. 8 shows a perspective view of the coupling element of the screw shown in FIG. 1,

[0031] FIG. 9 shows a section through a screw with larger angular play,

[0032] FIG. 10 shows a first side view of the screw shown in FIG. 9,

[0033] FIG. 11 shows a second side view of the screw shown in FIG. 9,

[0034] FIG. 12 shows a three-dimensional view of the screw shown in FIG. 9,

[0035] FIG. 13 shows a coupling element with star body,

[0036] FIG. 14 shows a section through two coupling elements, which cooperate in a positive manner by means of claws,

[0037] FIG. 15 shows a view of a coupling element according to FIG. 14,

[0038] FIG. 16 shows a three-dimensional view of two cooperating coupling elements according to FIG. 14,

[0039] FIG. 17 shows a screw according to FIGS. 9 to 12 in an orientation with head part, which is arranged offset parallel to the threaded part, and

[0040] FIG. 18 shows the screw shown in FIG. 17, inserted between fibula and tibia.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0041] The screw 1 shown in FIG. 1 has a head part 2 and a threaded part 3. As flexible joint part 4, provision is made between the head part 2 and the threaded part 3 for a combination of a first coupling element 5 with a plug-in connector 6 for transmitting torsional forces, and a second coupling element 7 for transmitting torsional forces. In the axial direction between head part 2 and threaded part 3, the first coupling element 5 of the flexible joint part 4 consists of 4 joint elements 8, 9, 10 and 11, which are arranged one behind the other.

[0042] The first coupling element 5 with the joint elements 8 to 11 has a central bore 12, which makes it possible to arrange a flexible wire inside the first coupling element 5 as second coupling element 7. This wire 13 is fixedly connected to the head part 2 and the threaded part 3 and thus allows the transmission of tensile forces between head part 2 and threaded part 3, while the wire only offers a very small resistance to torsional forces. The torsional forces are transmitted via the first coupling element 5 from the head part to the threaded part via a positive connection 14. For this purpose, the screw 1 is provided with a groove and tongue joint 15. In the case of this groove and tongue joint, the spring 16 is arranged in the groove 17 with an axial play of approximately 0.1 mm. In the case at hand, the play between the five joint elements, the head part and the threaded part at the five contact surfaces adds up to approximately 0.7 mm. This provides for a certain angular play around the longitudinal axis of the screw 1. For this purpose, the joint elements 8 to 11 are embodied annularly with a dovetail joint 18, which can be inserted into one another at right angles to the longitudinal axis of the screw, and which are secured against being detached and being displaced after being threaded onto the wire 13 of the second coupling element 7. For this purpose, the individual annular joint elements in each case have a bore 19, in which a rope, a cord, a chain, a tube, a rod or a coil can be arranged instead of the flexible wire shown in FIG. 2 as second coupling element 7, provided that these elements are suitable to allow a certain torsional force and to absorb a tensile force.

[0043] To fasten the second coupling element 7 in the head part 2, the first end 20 is arranged in the head part 2 and is welded at that location, while the second end 21 of the second coupling element 7 is welded in the threaded part 3.

[0044] The maximum diameter 22 of the coupling elements 8 to 11 is slightly smaller than the maximum diameter 23 of the threaded part 3.

[0045] The screw 30 shown in FIGS. 9 to 12 is made of a head part 31, a threaded part 32 and a flexible joint part 33, substantially like the screw 1. However, the screw 30 differs from the screw 1 by the formation of the flexible joint part 34. The first coupling element 35 has four joint elements 37, 38, 39 and 40, which are connected to one another and to the head part 31 and the threaded part 32 via a plug-in connection 36. The wire runs as second coupling element 41 inside these joint elements 37 to 40.

[0046] The screw 30 has a special groove and tongue joint 43 as positive connection 42, in the case of which a head part 44 has convex contact surfaces 45 in one view and concave contact surfaces 46 in a vertical view. The contact surfaces cooperate with correspondingly formed contact surfaces of an accommodation 47, which is arranged on the same joint element.

[0047] The special embodiment of the joint elements provides for a larger angular play around the longitudinal axis of the screw 30.

[0048] Provision can also be made for other positive connections in addition to the dovetail joint 18 provided in the case of the screw 1 and the special groove tongue joint 34 provided on the screw 30. FIG. 13 shows for example a three-part joint element 50 of a first holding part 51, which cooperates with claws 52 with a star-shaped central part 53, while the star-shaped central part 53 also cooperates with claws 54 of a second holding part 55. The holding parts 51 and 55 as well as the star-shaped central part 53 have central bores 56, 57 and 58, in which a flexible joint part (not shown) can be guided.

[0049] FIGS. 14 to 16 show a two-part coupling element 60, in the case of which joint elements 61 and 62 cooperate via claws 63 and 64, while both joint elements in each case have a central bore 65 and 66, in which a second coupling element (not shown) can be guided.

[0050] FIG. 17 shows the screw 30 shown in FIGS. 9 to 12 with a threaded part 32, which is arranged on a longitudinal axis 48, while the head part 31 is arranged on a longitudinal axis 49, which is located offset parallel thereto. In response to a rotation according to the arrow 70, the threaded part 32 rotates without play and without perceivable elasticity with the head part 31.

[0051] The screw 30 can thus be inserted for example between the tibia 71 and the fibula 72, in order to hold the fibula 72 against high forces acting in the Z-direction 73, while the flexible joint part 34 allows for a very high flexibility in the X- and Y-direction 74, in order to provide for a natural movement of the joint. The Z-direction thereby extends in the longitudinal axis of the screw, and the X- and Y-direction extend orthogonally thereto.

[0052] Although only a few embodiments of the present invention have been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.