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

A receiving part for receiving a rod for coupling the rod to a 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 defining an accommodation space for accommodating a head of the bone anchoring element, the head receiving portion having an open end, a central axis extending through the open end, and a flexible region to allow introduction and clamping of the head, wherein the flexible region has a first exterior surface portion positioned along the central axis between the rod receiving portion and a greatest diameter of the accommodation space, a second exterior surface portion positioned along the central axis between the greatest diameter of the accommodation space and the open end, and a groove between the first exterior surface portion and the second exterior surface portion;
• and
• a locking ring configured to be arranged around the head receiving portion, wherein the head receiving portion is expandable for introducing the head when the locking ring is around the head receiving portion in an insertion position, the locking ring having a first interior surface portion configured to move axially from the insertion position towards the open end of the head receiving portion to engage the first exterior surface portion of the head receiving portion at a first contact region to lock an angular position of the head relative to the head receiving portion, and a second interior surface portion configured to engage the second exterior surface portion of the head receiving portion at a second contact region, wherein the first interior surface portion is spaced apart from an end of the locking ring positioned closer to the open end of the head receiving portion when the locking ring is around the head receiving portion;
• wherein at the first contact region, one of the first exterior surface portion and the first interior surface portion comprises a cylindrical surface, and the other one of the first exterior surface portion and the first interior surface portion comprises another cylindrical surface or a ring-shaped bulge portion.

A bone anchoring device comprising:

• a bone anchoring element comprising a shaft for anchoring in a bone and a head;
• and
• a receiving part comprising:
• a receiving part body comprising a rod receiving portion with a channel for receiving a rod, and a head receiving portion defining an accommodation space for accommodating the head, the head receiving portion having an open end, a central axis extending through the open end, and a flexible region to allow introduction and clamping of the head, wherein the flexible region has a first exterior surface portion positioned along the central axis between the rod receiving portion and a greatest diameter of the accommodation space, a second exterior surface portion positioned along the central axis between the greatest diameter of the accommodation space and the open end, and a groove between the first exterior surface portion and the second exterior surface portion;
• and
• a locking ring configured to be arranged around the head receiving portion, wherein the head receiving portion is expandable for introducing the head when the locking ring is around the head receiving portion in an insertion position, the locking ring having a first interior surface portion configured to move axially from the insertion position towards the open end of the head receiving portion to engage the first exterior surface portion of the head receiving portion at a first contact region to lock an angular position of the head relative to the head receiving portion, and a second interior surface portion configured to engage the second exterior surface portion of the head receiving portion at a second contact region, wherein the first interior surface portion is spaced apart from an end of the locking ring positioned closer to the open end of the head receiving portion when the locking ring is around the head receiving portion;
• wherein at the first contact region, one of the first exterior surface portion and the first interior surface portion comprises a cylindrical surface, and the other one of the first exterior surface portion and the first interior surface portion comprises another cylindrical surface or a ring-shaped bulge portion.

A method of coupling a rod to a bone or vertebra via a bone anchoring device, the bone anchoring device comprising an anchoring element having a shaft for anchoring in the bone or vertebra and a head, and a receiving part comprising a receiving part body comprising a rod receiving portion with a channel for receiving the rod, and a head receiving portion defining an accommodation space for accommodating the head, the head receiving portion having an open end, a central axis extending through the open end, and a flexible region to allow introduction and clamping of the head, wherein the flexible region has a first exterior surface portion positioned along the central axis between the rod receiving portion and a greatest diameter of the accommodation space, a second exterior surface portion positioned along the central axis between the greatest diameter of the accommodation space and the open end, and a groove between the first exterior surface portion and the second exterior surface portion, and a locking ring configured to be arranged around the head receiving portion, wherein the head receiving portion is expandable for introducing the head when the locking ring is around the head receiving portion in an insertion position, the locking ring having a first interior surface portion and a second interior surface portion, wherein the first interior surface portion is spaced apart from an end of the locking ring positioned closer to the open end of the head receiving portion when the locking ring is around the head receiving portion, wherein one of the first exterior surface portion and the first interior surface portion comprises a first cylindrical surface, and the other one of the first exterior surface portion and the first interior surface portion comprises a second cylindrical surface or a ring-shaped bulge portion, the method comprising:

• inserting the bone anchoring device into the bone or vertebra;
• adjusting an angular position of the receiving part relative to the bone anchoring element;
• inserting the rod into the channel;
• and
• advancing a closure element into the channel to push the rod against the locking ring and to move the locking ring towards the open end of the head receiving portion to a locking position where the first cylindrical surface engages the second cylindrical surface or the ring-shaped bulge portion at a first contact region to lock an angular position of the head relative to the head receiving portion, and the second interior surface portion engages the second exterior surface portion at a second contact region.