System of a bone anchor and an elongate instrument
A system includes a bone anchor including a shank having a first end, a second end, a channel extending through the shank with a channel axis, and an internal advancement structure having at least a portion being closer axially to the second end than to the first end, and an elongate instrument configured to extend through the channel, with a tip portion and an external advancement structure configured to cooperate with the internal advancement structure. Engagement between the advancement structures facilitates holding of the tip portion at a first axial position relative to the bone anchor and movement of the tip portion from the first axial position towards both the first and second ends of the shank. The tip portion and the external advancement structure of the elongate instrument are insertable into and removable from the channel via the first end of the shank.
1. A system comprising:
a bone anchor comprising a shank having a first end, a second end opposite the first end, and an inner wall defining an annular region at the first end that forms a closed ring and a channel that extends through the shank from the annular region at the first end to the second end along a channel axis, wherein an internal advancement structure is provided on the inner wall; and
an elongate instrument configured to extend through the channel to a position closer axially to the second end of the shank than to the first end of the shank, the elongate instrument comprising a tip portion and an external advancement structure configured to cooperate with the internal advancement structure of the bone anchor;
wherein an engagement between the internal and external advancement structures is configured to hold the tip portion at a first axial position relative to the bone anchor, and wherein the tip portion is movable from the first axial position towards the first end of the shank and is movable from the first axial position away from the first end of the shank when the engagement is adjusted; and
wherein the tip portion and the external advancement structure of the elongate instrument are removable from the channel via the first end of the shank.
2. The system of claim 1 , wherein the internal advancement structure comprises an internal thread and the external advancement structure comprises an external thread.
3. The system of claim 2 , wherein the internal and the external threads are cylindrical threads.
4. The system of claim 1 , wherein the tip portion is movable in the channel from the first end of the shank to the second end of the shank.
5. The system of claim 4 , wherein the tip portion is movable to an axial position where the tip portion extends out of the second end of the shank.
6. The system of claim 1 , wherein the elongate instrument is configured to extend out of the first end of the shank when the tip portion is at or close to the second end of the shank.
7. The system of claim 1 , wherein the internal advancement structure and the external advancement structure are configured to cooperate to secure the elongate instrument relative to the bone anchor against axial displacement.
8. The system of claim 1 , wherein the elongate instrument further comprises a first engagement structure that is configured to cooperate with a second engagement structure of the bone anchor, of the elongate instrument, or of a further instrument, to prevent rotation of the elongate instrument relative to the bone anchor.
9. The system of claim 1 , wherein an axial length of the external advancement structure is greater than or equal to an axial length of the internal advancement structure.
10. The system of claim 1 , wherein the elongate instrument comprises a rear end opposite to the tip portion and a neck between the external advancement structure and the rear end and positioned close to the external advancement structure.
11. The system of claim 1 , wherein an axial length of the external advancement structure is smaller than an axial length of the internal advancement structure.
12. The system of claim 11 , wherein the axial length of the external advancement structure is sufficiently long to secure the elongate instrument against axial movement relative to the bone anchor.
13. The system of claim 1 , wherein the tip portion comprises at least one cutting edge that is configured to cut into bone.
14. The system of claim 1 , wherein a stop is provided at the inner wall of the shank to limit axial movement of the elongate instrument into the bone anchor.
15. The system of claim 14 , wherein the elongate instrument comprises a sensor element or a marker element.
16. The system of claim 1 , wherein the elongate instrument comprises a tube.
17. The system of claim 1 , wherein the elongate instrument is monolithic.
18. The system of claim 1 , further comprising a tool having a first portion configured to hold the shank and a second portion configured to hold the elongate instrument, such that the elongate instrument is configured to be axially and rotationally fixed relative to the shank.
19. The system of claim 1 , wherein at least part of the internal advancement structure is closer axially to the second end of the shank than to the first end of the shank.
20. A method of anchoring a bone anchor to a bone with an elongate instrument, the bone anchor comprising a shank having a first end, a second end, and an inner wall defining a channel extending through the shank from the first end to the second end and having a channel axis, wherein an internal advancement structure is provided on the inner wall, the elongate instrument configured to extend through the channel to a position closer axially to the second end of the shank than to the first end of the shank, the elongate instrument comprising a tip portion and an external advancement structure configured to cooperate with the internal advancement structure of the bone anchor, the method comprising:
inserting the tip portion and the external advancement structure of the elongate instrument into the channel;
engaging the internal and external advancement structures with one another to move the tip portion to a desired axial position relative to the bone anchor, such that the engagement between the internal and external advancement structures holds the tip portion at the desired axial position, and wherein the tip portion is movable from the desired axial position towards the first end of the shank and is movable from the desired axial position away from the first end of the shank when the engagement is adjusted;
anchoring the shank of the bone anchor to the bone; and
removing the tip portion and the external advancement structure of the elongate instrument from the channel via the first end of the shank.
21. The method of claim 20 , wherein the tip portion is configured to facilitate placement or implantation of the bone anchor at a desired position and/or orientation at the bone.
22. The system of claim 1 , wherein the tip portion is configured to be fixed axially relative to and to move together axially with the external advancement structure.
23. The system of claim 1 , wherein the bone anchor further comprises a head at the first end of the shank having an annular region that forms a closed ring and an outer width that is greater than an outer width of the first end of the shank.