Bone anchoring device and tool cooperating with such a bone anchoring device

A tool for a bone anchoring device comprising a bone anchoring element having a shank and a head, a receiving part comprising a rod receiving portion with a first end, a second end, and a U-shaped recess for receiving a rod, the recess extending from the first end in a direction of the second end and defining two free legs, a head receiving portion at the second end accommodating the head of the bone anchoring element, the head receiving portion having a free end and being flexible for introducing and clamping the head, and a locking ring around the head receiving portion, the locking ring comprising an engagement structure defining a width of the locking ring that is greater than a greatest width of the rod receiving portion, wherein the locking ring can assume a locking position where the locking ring compresses the head receiving portion of the receiving part to lock the head, the tool configured to move the locking ring out of the locking position towards the first end of the rod receiving portion, the tool comprising:

• a tubular member having a first end, a second end, and an engagement portion at an inner wall of the first end for engaging the engagement structure of the locking ring;
• and
• a shaft insertable into the tubular member and movable relative to the tubular member in an axial direction, the shaft having a first end;
• wherein when the locking ring is in the locking position and the head is locked relative to the receiving part and the engagement portion of the tubular member engages the engagement structure of the locking ring, the first end of the shaft abuts against the rod receiving portion of the receiving part, such that the shaft is configured to move relative to the tubular member to move the locking ring out of the locking position towards the first end of the rod receiving portion to release the locking of the head.

A method of unlocking a bone anchoring device from a locked position, the bone anchoring device comprising a bone anchoring element having a shank and a head, a receiving part comprising a rod receiving portion with a first end, a second end, and a U-shaped recess for receiving a rod, the recess extending from the first end in a direction of the second end and defining two free legs, a head receiving portion at the second end accommodating the head of the bone anchoring element, the head receiving portion having a free end and being flexible for introducing and clamping the head, and a locking ring around the head receiving portion, the locking ring comprising an engagement structure defining a width of the locking ring that is greater than a greatest width of the rod receiving portion, wherein when the locking ring is in the locked position, the locking ring compresses the head receiving portion of the receiving part and locks the head, the method comprising:

• attaching a tool to the bone anchoring element, the tool comprising a tubular member having a first end, a second end, and an engagement portion at an inner wall of the first end, and a shaft in the tubular member and movable relative to the tubular member in an axial direction, the shaft having a first end, the attaching comprising engaging an engagement portion at an inner wall of the first end of the tubular member to the engagement structure of the locking ring, such that the first end of the shaft abuts against the rod receiving portion of the receiving part;
• and
• moving the shaft relative to the tubular member to move the locking ring out of the locking position towards the first end of the rod receiving portion to release the locking of the head.