Rod-shaped implant, in particular for the dynamic stabilization of the spine
A rod-shaped implant for the dynamic stabilization of the spine includes at least a portion having a flexible first material forming a matrix in which a flexible structure having at least one fiber made of a second material is embedded. The rod-shaped implant can be compressed and extended along the longitudinal axis of the rod-shaped implant while it provides a high torsional stiffness.
1. A rod-shaped implant for the dynamic stabilization of the spine, the rod-shaped implant comprising:
a rod-shaped portion comprising a flexible first material forming a matrix; and
a flexible structure embedded inside the matrix and comprising:
two first fibers comprising a second material different from the first material and formed in first helical springs to increase torsional stiffness of the flexible structure in a first direction; and
two second fibers comprising a third material different from the first material and formed in second helical springs to increase torsional stiffness of the flexible structure in a second direction different from the first direction;
wherein outer diameters of each of the second helical springs is smaller than inner diameters of each of the first helical springs, and wherein each of the first fibers has two free ends and is entirely spaced apart from the other first fiber in the matrix, and each of the second fibers has two free ends and is entirely spaced apart from the other second fiber in the matrix.
2. The rod-shaped implant of claim 1 , wherein the first material is a polymer.
3. The rod-shaped implant of claim 1 , wherein the first material is an elastomeric material.
4. The rod-shaped implant of claim 1 , wherein at least one of the second material and the third material is a synthetic material.
5. The rod-shaped implant of claim 1 , wherein at least one of the second material and the third material is polypropylene.
6. The rod-shaped implant of claim 1 , wherein the first helical springs are rotated against the second helical springs by an angle.
7. The rod-shaped implant of claim 6 , wherein the angle is 180°.
8. The rod-shaped implant of claim 1 , wherein the first helical springs have the same diameter.
9. The rod-shaped implant of claim 1 , wherein the first helical springs have different diameters.
10. The rod-shaped implant of claim 1 , wherein the second helical springs have the same diameter.
11. The rod-shaped implant of claim 1 , wherein the second helical springs have different diameters.
12. The rod-shaped implant of claim 1 , wherein the flexible structure defines a net-like structure configured to enhance torsional stiffness.
13. The rod-shaped implant of claim 1 , wherein the second helical springs define an inner coaxial net-like structure and wherein the first helical springs define an outer coaxial net-like structure arranged around the inner structure.
14. The rod-shaped implant of claim 1 , wherein the flexible structure comprises four first fibers configured in four first helical springs to define a net-like outer structure and four second fibers configured in four second helical springs to define a net-like inner structure.
15. The rod-shaped implant of claim 14 , wherein the second helical springs of the inner structure are rotated against each other by 90° and the first helical springs of the outer structure are rotated against each other by 90°.
16. The rod-shaped implant of claim 14 , wherein the inner structure and the outer structure are rotated against each other by 180°.
17. The rod-shaped implant of claim 1 , wherein the flexible first material forming the matrix is cylindrical.
18. A bone anchoring assembly for dynamic stabilization of the spine comprising:
a first bone anchoring element configured for attachment to a bone or vertebrae;
a second bone anchoring element configured for attachment to a bone or vertebrae; and
a rod-shaped implant configured to connect the first bone anchoring element to the second bone anchoring element, the rod-shaped implant comprising:
a rod-shaped portion comprising a flexible first material forming a matrix; and
a flexible structure embedded inside the matrix and comprising:
two first fibers comprising a second material different from the first material and formed in first helical springs to increase torsional stiffness of the flexible structure in a first direction; and
two second fibers comprising a third material different from the first material and formed in second helical springs to increase torsional stiffness of the flexible structure in a second direction different than the first direction;
wherein outer diameters of each of the second helical springs is smaller than inner diameters of each of the first helical springs, and wherein each of the first fibers has two free ends and is entirely spaced apart from the other first fiber in the matrix, and each of the second fibers has two free ends and is entirely spaced apart from the other second fiber in the matrix.
19. A method of using a rod-shaped implant for dynamic stabilization of the spine with a first bone anchoring element configured for attachment to a bone or vertebrae, a second bone anchoring element configured for attachment to a bone or vertebrae, and a rod-shaped implant configured to connect the first bone anchoring element to the second bone anchoring element, the rod-shaped implant comprising a rod-shaped portion comprising a flexible first material forming a matrix, and a flexible structure embedded inside the matrix and comprising two first fibers comprising a second material different from the first material and formed in first helical springs to increase torsional stiffness of the flexible structure in a first direction, and two second fibers comprising a third material different from the first material and formed in second helical springs to increase torsional stiffness of the flexible structure in a second direction different than the first direction, wherein outer diameters of each of the second helical springs is smaller than inner diameters of each of the first helical springs, and wherein each of the first fibers has two free ends and is entirely spaced apart from the other first fiber in the matrix, and each of the second fibers has two free ends and is entirely spaced apart from the other second fiber in the matrix, the method comprising:
attaching the first bone anchoring element to a bone or vertebrae;
attaching the second bone anchoring element to a bone or vertebrae;
connecting the rod-shaped implant to the first bone anchoring element; and
connecting the rod-shaped implant to the second bone anchoring element.
20. A rod-shaped implant for the dynamic stabilization of the spine, the rod-shaped implant comprising:
a rod-shaped portion comprising a flexible first material forming a matrix and defining a longitudinal axis; and
a flexible monolithic net or web structure embedded inside the matrix and comprising:
at least a first helical portion made of a second material different from the first material and rotating in a first direction about the longitudinal axis; and
at least a second helical portion made from the second material and rotating in a second direction about the longitudinal axis opposite from the first direction;
wherein the diameters of the first helical portion and the second helical portion are the same, and wherein a portion of the first helical portion located between ends of the first helical portion intersects a portion of the second helical portion located between ends of the second helical portion at an intersecting portion and the intersecting portion forms both a part of the first helical portion and the second helical portion intersect.