Polyaxial bone anchoring device with enlarged pivot angle

1. A receiving part for coupling a rod to a bone anchoring element, the receiving part comprising:

a top end, a bottom end, and a longitudinal axis that extends from the top end toward the bottom end;

two arms defining a channel open to the top end for receiving the rod, wherein the channel extends perpendicularly to the longitudinal axis through opposing sides of the receiving part, and wherein a width of the channel at the first end is substantially the same for both of the opposing sides of the receiving part;

an opening at the bottom end for the bone anchoring element, wherein the longitudinal axis extends through the opening; and

an inner surface in which an internal groove having a bottom is formed, wherein the internal groove extends circumferentially around a central axis that is oriented at an angle oblique to the longitudinal axis.

2. The receiving part of claim 1 , wherein the internal groove is substantially symmetrical with respect to the central axis.

3. The receiving part of claim 1 , wherein a first passage extends coaxially with the central axis from the bottom end toward the top end, and a second passage extends coaxially with the longitudinal axis from the top end toward the bottom end.

4. The receiving part of claim 1 , wherein the channel is formed by a substantially U-shaped recess extending from the top end.

5. The receiving part of claim 1 , further comprising a locking element configured to be advanced along the longitudinal axis into the channel for locking the position of the receiving part relative to the bone anchoring element.

6. The receiving part of claim 5 , wherein the locking element is configured to urge an inserted rod toward the bottom end of the receiving part, which clamps a head of the bone anchoring element in the receiving part to lock the receiving part and the bone anchoring element from further movement relative to one another.

7. The receiving part 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 a head of the bone anchoring element, such that the head is insertable into the receiving part from the bottom end.

8. The receiving part of claim 1 , wherein the receiving part is configured to allow pivoting of the bone anchoring element in a symmetrical manner relative to the central axis.

9. A polyaxial bone anchoring device comprising the receiving part of claim 1 and an inner member positionable at least partially in the internal groove, the inner member defining a seat for a head of the bone anchoring element.

10. The polyaxial bone anchoring device of claim 9 , wherein the inner member has at least one slit to facilitate expansion and/or compression.

11. The polyaxial bone anchoring device of claim 9 , wherein the inner member is configured to cover at least a portion of the head from an upper side of the head.

12. The polyaxial bone anchoring device of claim 9 , 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.

13. The polyaxial bone anchoring device of claim 9 , wherein the internal groove provides space to facilitate expansion of the inner member when the head is inserted therein.

14. The polyaxial bone anchoring device of claim 9 , wherein the inner member has a spherically-shaped outer wall.

15. The polyaxial bone anchoring device of claim 9 , wherein the inner member has a spherically-shaped hollow interior forming the seat for the head.

16. The polyaxial bone anchoring device of claim 9 , wherein the inner member has a diameter that is smaller than a diameter of the head.

17. A receiving part for coupling a rod to a bone anchoring element, the receiving part comprising:

a top end, a bottom end, and a longitudinal axis that extends from the top end toward the bottom end;

two arms at the top end defining a channel for receiving the rod;

an opening at the bottom end for the bone anchoring element, wherein the longitudinal axis extends through the opening; and

an inner surface in which an internal groove having a bottom is formed, wherein the internal groove extends circumferentially around a central axis that is oriented at an angle oblique to the longitudinal axis, with a side of the internal groove that extends closer axially to the top end oriented radially toward one of the two arms, and with an opposite side of the internal groove that extends closer axially to the bottom end oriented radially toward the other one of the two arms.

18. The receiving part of claim 17 , wherein an axial distance between the top end of the receiving part and at least part of a downward facing surface at the bottom end that is oriented radially toward the one of the two arms is less than an axial distance between the top end and another part of the downward facing surface that is oriented radially away from the one of the two arms.

19. A polyaxial bone anchoring device comprising the receiving part of claim 17 and an inner member positionable at least partially in the internal groove, the inner member defining a seat for a head of the bone anchoring element.

20. A receiving part for coupling a rod to a bone anchoring element, the receiving part comprising:

a top end, a bottom end, and a longitudinal axis that extends from the top end toward the bottom end;

two arms at the top end defining a channel for receiving the rod;

an opening at the bottom end for the bone anchoring element, wherein the longitudinal axis extends through the opening; and

an inner surface in which an internal groove having a bottom is formed, wherein the internal groove extends circumferentially around a central axis that is oriented at an angle oblique to the longitudinal axis, with a side of the internal groove that extends closer axially to the top end oriented in a first radial direction toward one of the two arms;

wherein an axial distance between the top end of the receiving part and at least part of a downward facing surface at the bottom end that is oriented in the first radial direction is less than an axial distance between the top end and another part of the downward facing surface that is oriented away from the first radial direction.

21. A polyaxial bone anchoring device comprising the receiving part of claim 20 and an inner member positionable at least partially in the internal groove, the inner member defining a seat for a head of the bone anchoring element, wherein when the inner member is positioned at least partially in the internal groove, the central axis defines an axis of rotation of the inner member.

22. The polyaxial bone anchoring device of claim 19 , wherein when the inner member is positioned at least partially in the internal groove, the central axis defines an axis of rotation of the inner member.

23. The polyaxial bone anchoring device of claim 9 , wherein when the inner member is positioned at least partially in the internal groove, the central axis defines an axis of rotation of the inner member.

24. The receiving part of claim 1 , wherein the internal groove has at least an annular region forming an endless ring that is oriented at the angle oblique to the longitudinal axis.