Elastic stabilization system for vertebral columns
A vertebral column implant for the elastic stabilization of motion segments ( 1, 2 ) comprising an elastically bendable connecting element ( 5 ) which can be passed through the seats ( 4 ) of a number of pedicle screws ( 3 ) having offset seat axes ( 6 a , 6 b , 6 c ) and be anchored. The connecting element is bendable elastically about every axis of its cross-section in such a way that the connecting element can be passed through, or inserted in, the seats of the screwheads, one behind the other, even when the seats are not situated on one and the same axis. The connecting element and the seat in the screwhead each have wholly, or in part, a structured surface, in such a way that the structured surface of the seat engages the structured surface of the connecting element, and shifting can be prevented in assembled condition.
1. A vertebral column implant comprising a connecting element and a plurality of bone screws, each screw having a seat in its screwhead for the connecting element, wherein the connecting element is bendable elastically about every axis of its cross-section in such a way that the connecting element can be passed through, or inserted in, the seats of the screwheads, one behind the other, even when the seats are not situated on one and the same axis; wherein the connecting element and the seat in the screwhead each have wholly, or in part, a structured surface, in such a way that the structured surface of the seat engages the structured surface of the connecting element, and shifting can be prevented in assembled condition; and wherein the structured surface of the seat and the structured surface of the connecting element each has a structure of annular grooves with channels of the grooves being substantially at right angles to the longitudinal axis of the connecting element.
2. The vertebral column implant according to claim 1 , characterized in that the elastic connecting element is a rod made of an elastic material.
3. The vertebral column implant according to claim 2 , characterized in that the elastic material consists of a biocompatible plastic which may be composed of one or more kinds of monomer components.
4. The vertebral column implant according to claim 3 , characterized in that the biocompatible plastic is a plastic on the basis of polyurethane.
5. The vertebral column implant according to claim 1 , characterized in that the elastic connecting element has a structure with one or more hollow spaces.
6. The vertebral column implant according to claim 5 , characterized in that the elastic connecting element has a tubular cross-section with a wall thickness variable along the connecting element, which wall thickness confers the desired variable stiffness upon the connecting element according to the position.
7. The vertebral column implant according to claim 6 , characterized in that the connecting element and the seat in the screwhead each have wholly or in part a structured surface, in such a way that the structured surface of the seat engages the structured surface of the connecting element and shifting can be prevented in assembled condition.
8. The vertebral column implant according to claim 7 , characterized in that the structured surfaces have a structure grooved substantially at right angles to the longitudinal axis of the connecting element.
9. The vertebral column implant according to claim 1 , characterized in that the seat of the screwhead has a slot so that the elastic connecting element can be inserted and anchored in the seat with elastic deformation.
10. The vertebral column implant according to claim 1 , characterized in that a grooved structure of the seat of the screwhead is continued into a plurality of bevels of the slot so that the elastic connecting element can be pre-positioned for verifying the correct spacing of the vertebrae.
11. The vertebral column implant according to claim 1 , characterized in that the connecting element has a round cross-section with a flat side so that the connecting element can be introduced into the seat with a reduced inside width and thereafter anchored by means of a rotation.
12. The vertebral column implant according to claim 1 , characterized in that the connecting element has a round cross-section with two parallel flat sides so that the connecting element can be introduced into the seat with a reduced inside width and thereafter anchored by means of a rotation.
13. The vertebral column implant according to claim 1 , characterized in that the connecting element has a hollow space about the longitudinal axis, which hollow space facilitates the elastic deformation for introduction into the seat.
14. The vertebral column implant according to claim 13 , characterized in that it comprises a plug which can be pushed into the hollow space after introduction of the connecting element into the seat.
15. The vertebral column implant according to claim 1 , characterized in that the seat of the screwhead is clampable, and the connecting element can be clamped after introduction.
16. The vertebral column implant according to claim 1 , characterized in that the seat of the screwhead has a hook device into which a wedge can be hooked with preload of the connecting element.
17. The vertebral column implant according to claim 1 , characterized in that the grooves on the connecting element have a pitch, the seat on the screwhead has the same grooves with pitch and thus acts like a nut, so that the connecting element can be screwed in and passed through the screwheads by rotation about the longitudinal axis.