Coupling assembly for coupling a rod to a bone anchoring element, kit of such a coupling assembly different rod receiving elements and bone anchoring device

A bone anchoring device comprising:

• a bone anchoring element having a shank for anchoring to a bone and a head;
• a rod;
• a coupling element, the coupling element comprising:
• a receiving part having a first end, a second end and a central axis extending though the first end and the second end, a recess for receiving the rod, and an accommodation space for accommodating the head of the bone anchoring element, the accommodation space having an opening at the second end for inserting the head;
• a pressure element configured to be positioned at least partly in the accommodation space, the pressure element having a first end comprising a first end surface and a second end facing towards the second end of the receiving part, a central axis coaxial with the central axis of the receiving part, and a flexible portion to clamp an inserted head,
• a rod receiving element that is a separate part comprising a first end comprising a first end surface and a channel for inserting a rod adjacent to the first end and a second end having a second end surface facing towards the second end of the receiving part;
• wherein the first end surface of the pressure element is configured to extend into the channel of the rod receiving element;
• and
• a locking element that is configured to advance in axial direction in the receiving part for locking the head and the rod;
• wherein the pressure element comprises a portion that is configured to cooperate with a portion of the rod receiving element under axial load exerted by the locking element onto the rod receiving element such that either the portion of the pressure element or the portion of the rod receiving element is deformed so as to move the first end surface of the pressure element further into the channel of the rod receiving element in an axial direction.