Spinal implant set for the dynamic stabilization of the spine
A connection element ( 1 ) for stabilizing vertebral bodies that has a variable stiffness along its longitudinal axis in that particularly the cross-section of the connecting element varies along its longitudinal axis and extends over a plurality of bone screws ( 6 ). In spite of the varying cross-section (h 1 , h 2 ), in a preferred embodiment, the same bone screws ( 6 ) may be used in all locations by inserting clamping elements ( 9, 10 ) of different lengths.
1. A spinal implant set for dynamic stabilization of a spine, the spinal implant set comprising:
two or more bone screws; and
at least one elongated connection element having a cross section varying along a longitudinal axis of the elongated connection element,
wherein the cross section has two plane-parallel side faces extending in a direction of insertion of a bone screw, and a rearward side and a forward side, the rearward side and the forward side lying transverse to the direction of the insertion,
wherein the variation of the cross section is substantially accomplished by the variation of a distance between the rearward side and the forward side,
wherein the cross section variation is accomplished exclusively by at least one step comprised in the rearward side of the elongated connection element, and
wherein the forward side to be arranged in the seat of the bone screws toward the bone thread of the bone screw extends along a straight or curved line.
2. The spinal implant set of claim 1 , wherein said elongated connection element is straight.
3. The spinal implant set of claim 1 , wherein the varying cross section of the elongated connection element comprises a portion of constant cross section along the direction of the longitudinal axis such that the portion is insertable in at least two bone screws when implanted.
4. The spinal implant set of claim 1 , wherein the forward side of the elongated connection element comprises a rounded nose portion.
5. The spinal implant set of claim 4 , wherein the cross-section of the rounded nose portion of the elongated connection element substantially consists of a triangle with a rounded apex.
6. The spinal implant set of claim 4 , wherein the cross-section of the rounded nose portion of the elongated connection element substantially consists of a semi-circle.
7. The spinal implant set of claim 4 , wherein the cross-section of the rounded nose portion of the elongated connection element substantially consists of a semi-ellipse.
8. The spinal implant set of claim 1 , wherein the two or more bone screws comprise:
a first bone screw comprising a seat for the elongated connection element;
a second bone screw comprising a seat for the elongated connection element,
wherein the seat of the first bone screw is substantially identical to the seat for the elongated connection element of the second bone screw; and
the first bone screw comprises a first clamping insert insertable in the seat of the first bone screw; and
the second bone screw comprises a second clamping insert configured to be inserted in the seat of the second bone screw, such that the first and second clamping inserts compensate for the differing heights of the connection element.
9. The spinal implant set of claim 1 , wherein a reduced cross section portion is at at least one end of the elongated connection element.
10. The spinal implant set of claim 1 , wherein the elongated connection element is made of a plastic material.
11. The spinal implant set of claim 10 , wherein the plastic material is polycarbonate-urethane (PCU).
12. The spinal implant set of claim 10 , wherein the plastic material is of the family of polyetheretherketone (PEEK).
13. The spinal implant set of claim 1 , wherein the variation of the cross section of the elongated connection element comprises at least one step.
14. The spinal implant set of claim 1 , wherein said elongated connection element is pre-bent with at least one radius.
15. The method of claim 1 , wherein the at least one step comprises exactly one step.
16. The method of claim 1 , wherein the at least one step comprises exactly two steps.