Instrument for locking and unlocking a head of a bone anchor in a polyaxial bone anchoring device

A system comprising:

• a polyaxial bone anchoring device comprising a bone anchor for anchoring in a bone, a receiving part for receiving a head of the bone anchor, and a clamping device configured to clamp the head to lock the head relative to the receiving part;
• and
• an instrument connectable to the bone anchoring device to lock and unlock the head relative to the receiving part, the instrument comprising an actuator movable in a first direction from a first orientation to a second orientation,
• wherein the clamping device is movable relative to the receiving part, from a first position where the head is pivotable relative to the receiving part towards a second position where the head is locked relative to the receiving part, when the actuator is moved in the first direction, and
• wherein the clamping device is further movable from the second position back towards the first position when the actuator is moved in the first direction.

A method for using an instrument to lock and unlock a polyaxial bone anchoring device comprising a bone anchor, a receiving part for receiving a head of the bone anchor, and a clamping device for clamping the head, the method comprising:

• inserting a shank of the bone anchor into a bone;
• connecting the instrument to the bone anchoring device when the head is held in the receiving part;
• adjusting an angular position of the receiving part relative to the head;
• moving an actuator of the instrument in a first direction from a first orientation towards a second orientation to move the clamping device from a first position where the angular position of the receiving part remains adjustable relative to the head towards a second position where the receiving part is locked relative to the head;
• and
• moving the actuator of the instrument in the first direction to move the clamping device from the second position back towards the first position to unlock the receiving part relative to the head.