Receiving part for coupling a rod to a bone anchor

A bone anchoring device for coupling a rod to a bone anchor, the bone anchoring device comprising:

• a monolithic receiving part having a first end and a second end below the first end, the receiving part comprising:
• a rod receiving portion defining a recess at the first end for receiving the rod, the recess forming two legs each having an engagement surface for engaging a locking device to lock the rod in the recess;
• and
• a head receiving portion at the second end for receiving a head of the bone anchor, wherein at least one slit that extends from the second end to a closed end closer to the first end renders the head receiving portion expandable to permit insertion of the head into the head receiving portion and compressible to lock the head;
• and
• a separate ring positionable around and configured to engage an outer surface of the head receiving portion to urge the head receiving portion inwardly against the head, wherein the entire ring is positionable axially higher than the closed end of the slit;
• wherein when the ring is assembled to the receiving part, a stop on the receiving part positioned axially higher than a bottom of the recess of the receiving part facilitates movement of the ring to an uppermost first position where a majority of the ring is also positioned axially higher than the bottom of the recess to facilitate expansion of the head receiving portion for inserting the head;
• and
• wherein the ring is movable axially downwardly while a rotational orientation of the ring remains constant from the first position to a second position where the expansion of the head receiving portion is restricted and where the rod is insertable into and configured to be locked in the recess of the receiving part with the locking device.

A bone anchoring device for coupling a rod to a bone anchor, the bone anchoring device comprising:

• a receiving part having a first end, a second end below the first end, and a central axis extending between the first and second ends, the receiving part comprising a rod receiving portion defining a recess at the first end for receiving the rod, a head receiving portion at the second end for receiving a head of the bone anchor, and a coaxial central bore extending from the first end to the head receiving portion;
• and
• a separate ring positionable around and configured to engage an outer surface of the head receiving portion to urge the head receiving portion inwardly against the head;
• wherein at least one laterally extending channel that is spaced apart from the recess for the rod extends laterally through the receiving part from the central bore to outside the receiving part, and wherein a cross-sectional profile of the channel gradually increases in size over a majority of an entire lateral length of the channel as the channel extends outwardly through the receiving part.

A bone anchoring device for coupling a rod to bone, the bone anchoring device comprising:

• a bone anchor comprising a shank for anchoring to bone and a head;
• a monolithic receiving part having a first end, a second end below the first end, a central axis extending between the first and second ends, a recess at the first end for receiving the rod, an accommodation space for receiving the head of the bone anchor, and an opening at the second end for inserting the head into the accommodation space, wherein for at least one cross-section taken perpendicularly to the central axis, the receiving part forms an uninterrupted closed ring that extends entirely circumferentially around the central axis;
• and
• a separate locking device with a substantially cylindrical outer profile that movable in the recess to lock the rod in the recess of the receiving part;
• wherein the head and the rod are configured to be locked to the receiving part by only adjusting the locking device, without moving or adjusting any further part that is separable from the receiving part or the locking device relative to either the head or the receiving part, and while the head is configured to remain spaced apart from the rod.