Locking assembly for a polyaxial bone anchoring device

A method of coupling a rod to a bone or vertebra via a polyaxial bone anchoring device, the bone anchoring device comprising a bone anchoring element having a shank and a head, a receiving part configured to be coupled to the bone anchoring element and to pivotably receive the head, the receiving part having a recess with a substantially U-shaped cross-section for receiving the rod, the recess defining two legs, the legs having an internal advancement structure, a pressure element configured to contact the head to exert pressure on the head to lock an angular position of the head relative to the receiving part, and a locking assembly comprising a first locking element having a longitudinal axis, an outer surface with an external advancement structure configured to cooperate with the internal advancement structure of the legs, an inner wall defining a coaxial bore extending through the first locking element along the longitudinal axis, an internal advancement structure on a portion of the inner wall, and an engagement portion for a tool for advancing the first locking element relative to the receiving part, and a second locking element configured to be arranged at least partially in the first locking element, the second locking element having an outer surface with an external advancement structure configured to cooperate with the internal advancement structure of the first locking element, the method comprising:

• inserting the shank of the bone anchoring element into a bone or vertebra;
• adjusting the angular position of the receiving part relative to the bone anchoring element;
• inserting a rod into the recess of the receiving part, wherein the pressure element is positioned between the head and the rod;
• inserting the locking assembly into the recess;
• advancing the locking assembly in the receiving part towards the head, such that the first locking element is advanced axially in the receiving part at a first speed, and the second locking element moves axially relative to the receiving part at a speed different than the first speed, until the second locking element locks the head relative to the receiving part and the first locking element locks the rod relative to the receiving part.