Coupling assembly for coupling a rod to a bone anchoring element and bone anchoring device with such a coupling assembly

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

a receiving part with a first end and an opposite second end below the first end, a channel at the first end for receiving the rod, and an accommodation space at the second end for accommodating a head of the bone anchoring element;

an expandable seat positionable at least partially in the accommodation space to engage and hold the head in the accommodation space; and

a resilient ring separate from the seat that is configured to extend more than halfway around the central axis in a circumferential direction;

wherein when the seat is at an insertion position, the seat is expandable to facilitate insertion of the head into the accommodation space, while an abutment on the receiving part is configured to directly block the seat from moving upwardly towards the first end of the receiving part;

wherein the seat is adjustable from the insertion position to a pre-locking position where the seat is restricted from expanding to restrict the head from being removed from the accommodation space, while the ring is configured to directly block the seat from being adjusted back towards the insertion position; and

wherein when the seat is at a locking position, the head is locked relative to the receiving part.

2 . The coupling assembly of claim 1 , wherein the seat is formed as part of a pressure element that is further configured to engage the rod in the receiving part.

3 . The coupling assembly of claim 2 , wherein the pressure element is monolithic.

4 . The coupling assembly of claim 1 , wherein the ring is a slit ring.

5 . The coupling assembly of claim 1 , wherein the ring is expandable.

6 . The coupling assembly of claim 1 , wherein the receiving part comprises at least one pin, and wherein the abutment is formed on the at least one pin.

7 . The coupling assembly of claim 1 , wherein at least part of the seat is positionable axially lower than the ring when the seat and the ring are in the receiving part.

8 . A coupling assembly for coupling a rod to a bone anchoring element, the coupling assembly comprising:

a receiving part with a first end and an opposite second end below the first end, a channel at the first end for receiving the rod, and an accommodation space at the second end for accommodating a head of the bone anchoring element; and

a pressure element positionable at least partially in the accommodation space, the pressure element comprising head engaging surface configured to engage the head and a rod engaging surface that faces axially upwardly towards the first end of the receiving part to engage the rod;

wherein when the pressure element is at an insertion position, the pressure element is prevented from moving upwardly relative to the receiving part, the head is insertable into the accommodation space, and a surface of the pressure element that is positioned axially lower than a lowermost end of the rod engaging surface abuts against another part of the coupling assembly to restrict axial movement of the pressure element; and

wherein the pressure element is adjustable from the insertion position to a pre-locking position where the head is restricted from being removed from the accommodation space, while an uppermost surface of the pressure element, the entirety of which faces axially upwardly towards the first end of the receiving part, abuts against the receiving part to restrict the pressure element from being adjusted back towards the insertion position; and

wherein when the pressure element is at a locking position, the pressure element clamps and locks the head relative to the receiving part.

9 . The coupling assembly of claim 8 , wherein when the pressure element is at the insertion position, a seat for the head is expandable to facilitate insertion of the head into the accommodation space, and wherein when the pressure element is at the pre-locking position, the seat is restricted from expanding to restrict the head from being removed from the accommodation space.

10 . The coupling assembly of claim 9 , wherein the seat is formed as part of the pressure element.

11 . The coupling assembly of claim 8 , wherein the pressure element is at an uppermost position in the receiving part when at the insertion position.

12 . The coupling assembly of claim 8 , wherein the abutment at the insertion position restricts axial movement of the pressure element upwardly towards the first end of the receiving part.

13 . The coupling assembly of claim 8 , further comprising a holding element that is positionable at least partially in the receiving part, wherein the abutment at the insertion position is formed on the holding element.

14 . The coupling assembly of claim 13 , wherein the holding element comprises one or more pins.

15 . The coupling assembly of claim 8 , wherein when the pressure element is at the insertion position, the uppermost surface of the pressure element is configured to be spaced apart from the receiving part.

16 . The coupling assembly of claim 8 , wherein when the pressure element is at the insertion position, the pressure element is restricted from moving both axially upwardly and downwardly relative to the receiving part.

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

a receiving part with a first end and an opposite second end below the first end, a channel at the first end for receiving the rod, and an accommodation space at the second end for accommodating a head of the bone anchoring element; and

a pressure element positionable in the receiving part, the pressure element having an upper end, a lower end, a central axis that extends between the upper and lower ends, and two axially extending arms defining a recess that extends transversely through the pressure element along an axis of extension for receiving the rod;

wherein a surface of the pressure element that defines a bottom of the recess is substantially V-shaped for interchangeably contacting at least two rods with different diameters along two lines of contact that each extends substantially parallel to the axis of extension of the recess, wherein the two lines of contact are spaced apart from one another in a lateral direction that is perpendicular to a plane defined by the central axis and the axis of extension of the recess, and wherein a gap extends laterally away from either side of the substantially V-shaped surface to respectively space apart each of the two arms from the substantially V-shaped surface in the lateral direction; and

wherein when the head of the bone anchoring element and the pressure element are in the receiving part, the pressure element is movable relative to the receiving part to increase a clamping force on the head to lock the head relative to the receiving part.

18 . The coupling assembly of claim 17 , wherein the pressure element is configured to assume an insertion position where the head of the bone anchoring element is insertable from the second end of the receiving part into the accommodation space.

19 . The coupling assembly of claim 18 , wherein when the pressure element is at the insertion position, a seat for the head is expandable to facilitate insertion of the head into the accommodation space, and wherein the pressure element is adjustable from the insertion position to a pre-locking position where the seat is restricted from expanding to restrict the head from being removed from the accommodation space.

20 . The coupling assembly of claim 17 , wherein for at least one cross-sectional plane that is perpendicular to the central axis, each of the two arms is completely spaced apart from the substantially V-shaped surface in the lateral direction by the respective gap.