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

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

• a bone anchoring element comprising a shank and a head;
• a receiving part having a first end, a second end, a central axis extending through the first end and the second end, 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 compressible element defining a seat that is positionable in the accommodation space to directly engage the head to hold the head in the receiving part;
• and
• a separate ring-shaped element positionable in the receiving part;
• wherein when the bone anchoring element, the compressible element, and the ring-shaped element are assembled to the receiving part, the ring-shaped element is directly engageable with the compressible element and is rotatable around the central axis to adjust a force exerted by the compressible element on the head.

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

• a bone anchoring element comprising a shank and a head;
• a receiving part having a first end, a second end, a central axis extending through the first end and the second end, 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;
• and
• a clamping element comprising an unthreaded surface and at least one projection or recess that is formed on the unthreaded surface, wherein at least part of the clamping element is configured to extend into the accommodation space;
• wherein when the bone anchoring element and the clamping element are assembled to the receiving part, the clamping element is rotatable relative to another part of the bone anchoring device between a first position where the at least one projection or recess of the clamping element is out of engagement with a corresponding recess or projection of the bone anchoring device and a second position where the at least one projection or recess engages the corresponding recess or projection, and wherein rotation of the clamping element relative to the another part of the bone anchoring device facilitates holding of the head in the accommodation space.

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

• a bone anchoring element comprising a shank and a head;
• a receiving part having a first end, a second end, a central axis extending through the first end and the second end, 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;
• and
• an unthreaded clamping element that is positionable in the receiving part;
• wherein when the bone anchoring element and the clamping element are assembled to the receiving part, the clamping element is movable relative to another part of the bone anchoring device in a direction that is angled relative to the central axis from a first position to a second position to increase a clamping force on the head, wherein the clamping force on the head continuously increases as the clamping element moves from the first position to the second position, and wherein the clamping element is configured to be held at the first position, at the second position, and at a plurality of intermediate positions between the first position and the second position.