Dynamic bone anchor and method of manufacturing the same

1. A dynamic bone anchor comprising:

an anchor member having a first end and a second end, a tubular section between the first end and the second end having an inner surface defining a bore, the inner surface having an inner width, a longitudinal axis extending from the first end to the second end, an outer surface, and a bone engagement structure for engaging a bone on at least a portion of the outer surface; and

a longitudinal core member having a first portion and a second portion, the second portion configured to be received in the tubular section and to be connected thereto, wherein the second portion has a first outer width that defines a greatest outer width of the second portion, and wherein the second portion is made at least partially of a first material that comprises a shape memory alloy having a temperature sensitive property,

wherein in a first configuration where the anchor member and core member are separated and the core member is at a first temperature, the first outer width of the second portion of the core member is larger than the inner width of the tubular section of the anchor member and the first outer width is configured to be deformed by the tubular section during introduction of the core member into the tubular section, and

wherein in a second configuration where the core member is inserted into the anchor member and the core member is at a second temperature greater than the first temperature, the first outer width of the second portion of the core member engages the anchor member with a force greater than when the core member is at the first temperature, to connect the core member to the anchor member.

2. The dynamic bone anchor of claim 1 , wherein the first temperature is below a martensite finish temperature M f of the shape memory alloy and the second temperature is above an austenite finish temperature A f of the shape memory alloy.

3. The dynamic bone anchor of claim 1 , wherein the shape memory alloy is Nitinol.

4. The dynamic bone anchor of claim 1 , wherein the anchor member is made of a second material that is different from the first material.

5. The dynamic bone anchor of claim 2 , wherein in the second configuration, the core member is fixed to the anchor member by a press-fit connection achieved by a process including manufacturing at least the second portion of the core member with a predefined shape, cooling the second portion below the martensite finish temperature M f , deforming the second portion of the core member by reducing the first outer width during insertion into the anchor member to be less than or equal to the inner width of the tubular section of the anchor member, and heating the second portion after insertion into the anchor member thereby using the shape memory effect.

6. The dynamic bone anchor of claim 1 , wherein the first portion of the core member comprises an intermediate portion that has an outer width that is smaller than the inner width of the tubular section.

7. The dynamic bone anchor of claim 1 , wherein when the second portion of the core member is fully inserted in the tubular section and is connected to the tubular section, the first portion of the core member is deflectable from the longitudinal axis in a translational movement in a direction transverse to the longitudinal axis and/or in a rotational movement around the longitudinal axis.

8. The dynamic bone anchor of claim 7 , wherein the first portion of the core member projects out of the tubular section.

9. The dynamic bone anchor of claim 8 , wherein a free end of the first portion of the core member is connected to an anchor head having a width greater than the inner width of the tubular section.

10. The dynamic bone anchor of claim 9 , wherein the free end of the first portion of the core member is fixed to the anchor head by a press-fit connection achieved by a process including manufacturing the free end of the first portion of the core member with a predefined shape, cooling it below the martensite finish temperature M f , deforming it during insertion into the anchor head, and heating it after insertion into the anchor head thereby using the shape memory effect.

11. The dynamic bone anchor of claim 8 , wherein the free end of the first portion of the core member is shaped as an anchor head having a width greater than the inner width of the tubular section, the anchor head being monolithic with other parts of the first portion of the core member.

12. The dynamic bone anchor of claim 11 , wherein when the second portion of the core member is fully inserted in the tubular section and is connected to the tubular section, the anchor head is spaced a distance apart from the tubular section such that it can move with respect to the tubular section.

13. The dynamic bone anchor of claim 1 , wherein the anchor member comprises a tip at the second end.

14. The dynamic bone anchor of claim 1 , wherein the anchor member is open at the second end and wherein the core member extends through the open second end forming a tip of the bone anchor.

15. A dynamic bone anchor comprising:

an anchor member having a first end and a second end, a tubular section between the first end and the second end having an inner surface defining a bore, the inner surface having an inner width, a longitudinal axis extending from the first end to the second end, an outer surface, and a bone engagement structure for engaging a bone on at least a portion of the outer surface; and

a longitudinal core member having a first portion and a second portion, the second portion configured to be received in the tubular section and connected thereto, wherein the second portion has a first outer width that defines a greatest outer width of the second portion, and wherein the second portion is made at least partially of a first material that comprises a shape memory alloy having a temperature sensitive property, wherein the core member is configured to be fixed to the anchor member by a press-fit connection achieved by a process including manufacturing at least the first outer width of the second portion of the core member to have a greater width in an undeformed configuration than the inner width of the anchor member at a first temperature, introducing the second portion of the core member into the tubular section of the anchor member when the second portion is at the first temperature to deform the first outer width of the second portion, and increasing the temperature of the core member from the first temperature to a second temperature to expand the second portion of the core member towards the undeformed configuration after insertion into the anchor member to connect the core member to the anchor member.

16. The dynamic bone anchor of claim 15 , wherein the first temperature is below a martensite finish temperature M f of the shape memory alloy and the second temperature is above an austenite finish temperature A f of the shape memory alloy.

17. A dynamic bone anchor comprising:

an anchor member having an open first end and a second end, a tubular section between the first end and the second end, a longitudinal axis extending from the first end to the second end, an outer surface, and a bone engagement structure for engaging a bone on at least a portion of the outer surface, wherein the anchor member is made of a first material; and

a longitudinal core member having a first portion and a second portion, the second portion comprising a second end of the core member and configured to be inserted into the open first end of the anchor member to be received in the tubular section and connected thereto, the first portion extending from the second portion to a first end of the core member opposite the second portion, wherein the core member is made of a second material different from the first material, the first material being a stiffer material than the second material;

wherein when the second portion of the core member is fully inserted in the tubular section and is connected thereto, the first portion of the core member is deflectable from the longitudinal axis in a translational movement in a direction transverse to the longitudinal axis or in a rotational movement around the longitudinal axis.

18. The dynamic bone anchor of claim 17 , wherein the first end of the core member comprises an anchor head having a width larger than the greatest outer width of the second portion of the core member.

19. The dynamic bone anchor of claim 17 , wherein the second material is a shape memory alloy.