Polyaxial bone anchoring device with enlarged pivot angle

1. A polyaxial bone anchoring device comprising:

a bone anchoring element comprising a head and a shank;

a receiving part for coupling a rod to the bone anchoring element, the receiving part having a top end, a bottom end, a longitudinal axis, an opening at the bottom end, and a channel at the top end for receiving the rod, wherein the longitudinal axis extends through the opening at the bottom end, and wherein the receiving part further defines an internal groove oriented at an angle that is oblique to the longitudinal axis; and

an inner member positionable in the internal groove and having a seat configured to contact the head to hold the head in the receiving part while the shank extends through the opening at the bottom end of the receiving part.

2. The polyaxial bone anchoring device of claim 1 , wherein the seat is substantially symmetrical with respect to the angle that is oblique to the longitudinal axis.

3. The polyaxial bone anchoring device of claim 1 , wherein a first passage extends from the bottom end toward the top end, and a second passage extends from the top end toward the bottom end.

4. The polyaxial bone anchoring device of claim 3 , wherein the first passage and the second passage are in communication with one another.

5. The polyaxial bone anchoring device of claim 1 , wherein the channel is formed by a substantially U-shaped recess extending from the top end.

6. The polyaxial bone anchoring device of claim 1 , wherein the seat comprises a compressible wall configured to encompass at least a portion of the head to clamp the head.

7. The polyaxial bone anchoring device of claim 1 , wherein the seat has at least one slit that opens toward the bottom end of the receiving part.

8. The polyaxial bone anchoring device of claim 1 , wherein the head has a spherically-shaped outer surface portion including a greatest diameter of the sphere, and wherein the seat has a substantially concave surface portion adapted to engage at least an outer surface portion of the head that includes the greatest diameter of the sphere.

9. The polyaxial bone anchoring device of claim 1 , further comprising a locking element configured to be advanced in the receiving part for locking a position of the head relative to the receiving part.

10. The polyaxial bone anchoring device of claim 9 , wherein the locking element is configured to urge an inserted rod toward the bottom end of the receiving part, which clamps the head in the seat to lock the receiving part and the bone anchoring element from further movement relative to one another.

11. The polyaxial bone anchoring device of claim 1 , wherein the receiving part defines at least part of the seat.

12. The polyaxial bone anchoring device of claim 1 , wherein the inner member is configured to cover at least a portion of the head from an upper side of the head.

13. The polyaxial bone anchoring device of claim 1 , wherein the inner member is movable in the internal groove, and wherein movement of the inner member toward the top end of the receiving part is restricted by a stop.

14. The polyaxial bone anchoring device of claim 1 , wherein the opening at the bottom end of the receiving part has a diameter that is greater than a greatest diameter of the head.

15. The polyaxial bone anchoring device of claim 1 , wherein the seat is configured to allow pivoting of the bone anchoring element in a symmetrical manner relative to the angle that is oblique to the longitudinal axis.

16. The polyaxial bone anchoring device of claim 1 , wherein the longitudinal axis is perpendicular to a longitudinal axis of the channel for receiving the rod.

17. The polyaxial bone anchoring device of claim 14 , wherein the head is insertable into the receiving part from the bottom end.

18. The polyaxial bone anchoring device of claim 3 , wherein the second passage extends coaxially with the longitudinal axis, the first passage extends coaxially with the angle that is oblique to the longitudinal axis, and the angle that is oblique to the longitudinal axis intersects the longitudinal axis.

19. The polyaxial bone anchoring device of claim 1 , wherein the seat opens towards the opening at the bottom end to allow pivoting of the head relative to the seat.

20. The polyaxial bone anchoring device of claim 1 , wherein the inner member has a spherically-shaped outer wall.

21. The polyaxial bone anchoring device of claim 1 , wherein the inner member has a spherically-shaped hollow interior forming the seat for the head.

22. The polyaxial bone anchoring device of claim 1 , wherein the inner member has a diameter that is smaller than a diameter of the head of the bone anchoring element.

23. The polyaxial bone anchoring device of claim 1 , wherein an engagement feature is formed on an outer surface of the receiving part at or near the top end.

24. A polyaxial bone anchoring device comprising:

a bone anchoring element comprising a shank for anchoring to a bone and a head;

a receiving part for coupling a rod to the bone anchoring element, the receiving part having a top end defining a first opening, a bottom end defining a second opening, and a longitudinal axis that extends through the first opening and the second opening, the receiving part comprising a base and two arms extending from the base to the top end to define a channel for receiving the rod, wherein the base further defines an internal groove oriented at an angle that is oblique to the longitudinal axis; and

an inner member positionable in the internal groove at an angle that is oblique to the longitudinal axis, the inner member having a seat configured to contact the head to hold the head in the receiving part while the shank extends through the second opening at the bottom end of the receiving part.