Receiving part for receiving a rod for coupling the rod to a bone anchoring element and bone anchoring device with such a receiving part

A bone anchoring device comprising:

• a bone anchoring element having a threaded shaft and a head;
• and
• a receiving part for receiving a rod for coupling the rod to the bone anchoring element, the receiving part comprising:
• a receiving part body comprising a rod receiving portion with a channel for receiving the rod, and a head receiving portion for accommodating the head of the bone anchoring element, the head receiving portion having an open end and being flexible for inserting and clamping of the head, and an exterior surface with a curved portion;
• and
• a locking ring around the head receiving portion, wherein the locking ring has an interior surface with a curved portion for engagement with the curved portion of the exterior surface of the head receiving portion for locking a position of the head relative to the head receiving portion.

A method of coupling a rod to a bone anchoring element via a receiving part, the receiving part comprising a rod receiving portion with a channel for receiving the rod, a head receiving portion having an open end and being flexible for inserting and clamping of a head of the bone anchoring element and an exterior surface with a curved portion, and a locking ring around the head receiving portion and having an interior surface with a curved portion for engagement with the curved portion of the exterior surface of the head receiving portion, the method comprising:

• introducing the head of the bone anchoring element into the open end of the head receiving portion;
• pivoting the head receiving portion relative to the head to align the receiving part with the rod;
• inserting the rod into the channel of the rod receiving portion;
• advancing a closure element in the channel to push the rod against the locking ring;
• and
• further advancing the closure element in the channel towards the head receiving portion to force the locking ring towards the open end of the head receiving portion via the rod and to lock a position of the rod relative to the receiving part,
• wherein advancement of the locking ring towards the open end of the head receiving portion engages the curved portion of the locking ring with the curved portion of the exterior surface of the head receiving portion to compress the head receiving portion and lock the position of the bone anchoring element relative to the receiving part.