Dynamic bone anchor
A dynamic bone anchor includes a longitudinal core member having a first end and a second end, and a longitudinal axis extending through the first end and the second end. The dynamic bone anchor further includes a plurality of tubular segments configured to be positioned around the core member, each of the tubular segments having a bone engagement structure on an outer surface thereof. In a first assembled configuration between the core member and the tubular segments, each of the tubular segments is individually movable on the core member along the longitudinal axis independent of the core member, itself, and the other tubular segments.
1. A dynamic bone anchor comprising:
a longitudinal core member having a first end and a second end, a longitudinal axis extending through the first end and the second end, and at least one connection portion having a larger cross section than a cross section of a second portion of the core member;
a plurality of tubular segments configured to be positioned around the core member, each of the tubular segments having a bone engagement structure on an outer surface thereof;
wherein in a first assembled configuration, each of the tubular segments is movable on the core member along the longitudinal axis and the at least one connection portion of the core member prevents rotation of the plurality of tubular segments relative to the core member.
2. The dynamic bone anchor of claim 1 , wherein in the first assembled configuration the core member is configured to be movable relative to the tubular segments in a direction transverse to the longitudinal axis.
3. The dynamic bone anchor of claim 1 , wherein in the first assembled configuration, each of the tubular segments is configured to slide along the core member and is fixed against rotation around the longitudinal axis.
4. The dynamic bone anchor of claim 1 , wherein an inner surface of each of the tubular segments comprises a contour having a non-circular shape in a plane perpendicular to the longitudinal axis, and wherein the at least one connection portion is configured to couple to at least one of the tubular segments with a corresponding outer contour of the core member.
5. The dynamic bone anchor of claim 4 , wherein the contour of the tubular segments is square-shaped.
6. The dynamic bone anchor of claim 1 , wherein an outer surface of each of the tubular segments comprises a bone thread.
7. The dynamic bone anchor of claim 6 , wherein in a second assembled configuration where the tubular segments are not moveable on the core member, a continuous bone thread is provided along the outer surface of the tubular segments.
8. The dynamic bone anchor of claim 7 , wherein the bone anchor is configured to move from the first assembled configuration into the second assembled configuration.
9. The dynamic bone anchor of claim 7 , wherein the bone anchor is configured to move from the second assembled configuration into the first assembled configuration.
10. The dynamic bone anchor of claim 1 , wherein in the first assembled configuration, a first stop and a second stop on the core member are configured to limit the motion of the tubular segments along the longitudinal axis.
11. The dynamic bone anchor of claim 10 , wherein the first stop comprises a tip member at or near the first end of the core member, the tip member being a connectable tip member.
12. The dynamic bone anchor of claim 10 , further comprising a head at or near a second end of the core member, the head comprising the second stop.
13. The dynamic bone anchor of claim 12 , wherein the head is configured to slide along the core member such that the head can move against the tubular segments.
14. The dynamic bone anchor of claim 13 , wherein the core member comprises a traction portion at its second end, and wherein the bone anchor is configured to be brought into a second assembled configuration by pulling the core member and traction portion and pressing the head against the tubular segments such that the tubular segments are fixed with respect to the core member.
15. The dynamic bone anchor of claim 14 , wherein the core member comprises a predetermined break-off section located a distance from its second end.
16. The dynamic bone anchor of claim 14 , wherein the head is configured to connect to the core member at an adjustable distance from the tubular segments along a longitudinal direction, and wherein the connection is by a threaded connection.
17. The dynamic bone anchor of claim 14 , wherein in the second assembled configuration, the tubular segments are fixed with respect to the core member.
18. The dynamic bone anchor of claim 1 , wherein the core member comprises a material having shape memory properties, wherein the core member is configured to assume a first length in the first assembled configuration and a second length in a second assembled configuration, and wherein the first length is greater than the second length.
19. The dynamic bone anchor of claim 18 , wherein the core member is configured to change from the second length to the first length upon an application of heat treatment.
20. The dynamic bone anchor of claim 1 , wherein the plurality of tubular segments comprises at least two tubular segments, and wherein a single connection portion is configured to bridge respective adjacent ends of two tubular segments.
21. The dynamic bone anchor of claim 1 , further comprising a head at the second end of the core member, wherein in the first assembled configuration, the head is moveable relative to the tubular segments in a direction transverse to the longitudinal axis.