Bone anchoring device

A bone anchoring device comprising:

• an anchoring element having a shaft for anchoring in a bone, the shaft having a shaft axis, and a head above the shaft, the head comprising a spherical segment-shaped outer surface that includes a greatest diameter of the sphere when measured in a direction perpendicular to the shaft axis, and a groove that extends circumferentially around the entire spherical segment-shaped outer surface, wherein the entire groove is positioned axially above the greatest diameter of the sphere on a side of the head opposite the shaft, and wherein the groove includes a first surface that is angled arranged at a non-zero angle relative to the shaft axis to face at least partially towards a free end of the head and a second surface that is arranged at a non-zero angle relative to the shaft axis to face at least partially away from the free end of the head;
• a receiving part having a first end and a second end below the first end, a recess for receiving a rod, a bore extending from the first end in the direction of the second end and configured to pivotably receive the head near the second end;
• and
• a pressure element movable in the bore for exerting pressure on the head to lock an angle of the head relative to the receiving part;
• wherein when the head and the pressure element are assembled to the receiving part, the pressure element is configured to simultaneously engage an entire circumference of the groove.

A bone anchoring device comprising:

• an anchoring element having a shaft for anchoring in a bone, the shaft having a shaft axis, and a head above the shaft, the head comprising a spherical segment-shaped outer surface that includes a greatest diameter of the sphere when measured in a direction perpendicular to the shaft axis;
• a receiving part having a first end and a second end, a recess for receiving a rod, a bore extending from the first end in the direction of the second end and configured to pivotably receive the head near the second end;
• a pressure element movable in the bore for exerting pressure on the head to lock an angle of the head relative to the receiving part, wherein a central axis of the pressure element is substantially fixed relative to a central axis of the receiving part such that the pressure element is pivotable together with the receiving part relative to the head when in contact with the head in the receiving part;
• and
• a ring that is radially expandable and compressible, wherein the ring is positionable in a groove formed on one of the receiving part or the pressure element;
• wherein when the head, the pressure element, and the ring are assembled to the receiving part and the shaft axis is coaxial with the central axis of the receiving part, the ring is configured to directly engage the head, and the entire ring is positioned axially above the greatest diameter of the sphere on a side of the head opposite the shaft and is restricted by the groove from moving axially towards the second end of the receiving part.