Polyaxial bone anchoring device

A bone anchoring device comprising:

• a receiving part comprising a first end, a second end below the first end, a longitudinal axis extending between the first and second ends, a channel at the first end for receiving a rod, and an accommodation space at the second end for pivotably holding a head of a bone anchoring element;
• and
• a pressure member movable in the receiving part, the pressure member comprising a rod engaging surface configured to extend into the channel to engage the rod, a pressure exerting surface configured to directly engage and exert pressure on the head, and an arm on either side of the rod engaging surface that extends towards the first end of the receiving part and that is flexible radially relative to the longitudinal axis;
• wherein at least part of the pressure member has a substantially cylindrical profile, wherein at least part of each of the arms extends farther radially from the longitudinal axis than the cylindrical profile to engage the receiving part for holding an axial position of the pressure member, and wherein the pressure member further comprises a projection on either side of the rod engaging surface that is separate from the respective arm and that also extends farther radially from the longitudinal axis than the cylindrical profile.

A bone anchoring device comprising:

• a bone anchoring element comprising a shank for anchoring to a bone and a head;
• a receiving part comprising a first end, a second end, a longitudinal axis extending through the first end and the second end, a channel at the first end for receiving a rod, and an accommodation space for pivotably holding the head;
• a pressure member positionable in the receiving part, the pressure member comprising a pressure exerting surface configured to directly engage and exert pressure on the head to lock the head in the receiving part, and a deformable portion;
• and a locking member configured to be inserted into the channel to move in the channel along the longitudinal axis;
• wherein when the head and the pressure member are in the receiving part, the locking member is moveable from the first end of the receiving part towards the head, wherein the locking member is configured to directly engage the deformable portion for adjusting the deformable portion from a first configuration to a second configuration to increase a force exerted by the pressure exerting surface of the pressure member on the head to lock the head relative to the receiving part;
• and wherein when the deformable portion is at the second configuration, the locking member is movable in a direction away from the head and separable from the receiving part while the deformable portion remains at the second configuration and while a position of the pressure member remains substantially constant to keep the head locked.