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

A bone anchoring device comprising:

• a bone anchoring element comprising a head and a threaded shaft;
• 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 so as to allow introduction and clamping of the head and an exterior surface, wherein a longitudinal axis extends from the rod receiving portion to the head receiving portion;
• and
• a locking ring configured to be arranged around the head receiving portion and comprising an interior surface with a curved portion curving along a direction parallel to the longitudinal axis, wherein when the locking ring is around the head receiving portion, the locking ring is movable along the longitudinal axis between a first position wherein a space between the locking ring and the head receiving portion permits expansion of the head receiving portion for inserting the head, and a second position wherein the curved portion is configured to engage the exterior surface of the head receiving portion to clamp the head therein.

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 and a head receiving portion for accommodating a head of the bone anchoring element, the head receiving portion having an open end and being flexible so as to allow introduction and clamping of the head and an exterior surface, wherein a longitudinal axis extends for the rod receiving portion to the head receiving portion, and a locking ring around the head receiving portion and comprising an interior surface with a curved portion curving along a direction parallel to the longitudinal axis, wherein the locking ring is movable along the longitudinal axis between a first position wherein a space between the locking ring and the head receiving portion permits expansion of the head receiving portion for inserting the head, and a second position wherein the curved portion is configured to engage the exterior surface of the head receiving portion to lock a position of the bone anchoring element relative to the receiving part, the method comprising:

• introducing the head of the bone anchoring element into the open end of the head receiving portion when the locking ring is in the first position;
• pivoting the head relative to the head receiving portion to be aligned with the rod;
• inserting the rod in 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 to the second position 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 to the second position engages the curved portion of the locking ring with the exterior surface of the head receiving portion to compress the head receiving portion and to lock the position of the bone anchoring element relative to the receiving part.