Coupling assembly for coupling a rod to a bone anchoring element, polyaxial bone anchoring device and modular stabilization device

A bone anchoring device for coupling a rod to bone, the bone anchoring device comprising:

• a bone anchoring element comprising a shank for anchoring to bone and a head;
• a receiving part having a first end, a second end below the first end, a central axis extending through the first and second ends, a channel at the first end for receiving the rod, and an accommodation space for accommodating the head of the bone anchoring element, the accommodation space defining an opening at the second end;
• a rod receiving element movable in the receiving part, wherein at least part of the rod receiving element is positionable axially lower in the receiving part than a bottom of the channel for the rod, wherein the rod receiving element comprises a rod contacting surface that forms a transverse recess for receiving the rod, and wherein the recess has an axial depth that is less than half of a greatest width of the recess;
• and
• a separate seat movable in the accommodation space, wherein the seat comprises an upwardly facing surface configured to directly engage and exert an upward pressure directed towards the first end of the receiving part on the head;
• wherein the seat is configured to assume an insertion position in the receiving part where the head of the bone anchoring element is insertable through the opening of the receiving part into the seat;
• and
• wherein the rod receiving element is movable downwardly to adjust the seat from the insertion position to a pre-locking position where the head is restricted from being removed through the opening of the receiving part, while an abutment that is positioned axially lower in the receiving part than a bottom of the rod receiving element restricts movement of the seat from the pre-locking position back towards the insertion position.

A bone anchoring device for coupling a rod to bone, the bone anchoring device comprising:

• a bone anchoring element comprising a shank for anchoring to bone and a head;
• a receiving part having a first end, a second end below the first end, a central axis extending through the first and second ends, a channel at the first end for receiving the rod, and an accommodation space at the second end for accommodating the head of the bone anchoring element;
• a first spring separable from and positionable in the receiving part and configured to extend more than halfway around the central axis in a circumferential direction;
• and
• a second spring separable from and positionable in the receiving part, wherein the second spring is sized and/or shaped differently from the first spring;
• wherein when the first and second springs are in the receiving part, at least part of each of the first and second springs is positionable axially lower in the receiving part than a bottom of the channel for the rod, and both the first and second springs are expandable in a radial direction relative to the central axis, with the first and second springs being expandable completely independently from one another;
• and
• wherein when the head is in the accommodation space, the first and second springs are pivotable together with the receiving part relative to the head.

A bone anchoring device for coupling a rod to bone, the bone anchoring device comprising:

• a bone anchoring element comprising a shank for anchoring to bone and a head;
• a receiving part having a first end, a second end below the first end, a central axis extending through the first and second ends, a channel at the first end for receiving the rod, and an accommodation space for accommodating the head of the bone anchoring element, the accommodation space defining an opening at the second end;
• and
• a seat positionable in the accommodation space for holding the head in the receiving part, wherein the seat is configured to extend continuously more than halfway around the central axis in a circumferential direction, while a slit extends completely through the seat to render the seat radially expandable, and wherein the seat defines a recessed portion that is spaced apart from the slit in the circumferential direction;
• wherein the seat is configured to assume an insertion position in the receiving part where the head of the bone anchoring element is insertable through the opening of the receiving part into the seat;
• and
• wherein when the head and the seat are in the receiving part with the recessed portion of the seat oriented at a first radial direction relative to the central axis, the recessed portion facilitates pivoting of the bone anchoring element to a greater angle relative to the receiving part in the first radial direction than in another radial direction different from the first radial direction.