Coupling device for coupling a rod to a bone anchor and system including such a coupling device and at least two bone anchors

A system for coupling a rod to bone, the system comprising:

• a first bone anchor comprising a first shank for anchoring to bone and a first head;
• a second bone anchor different from the first bone anchor and comprising a second shank for anchoring to bone and a second head;
• and
• a coupling device comprising:
• a receiving part having a first end, an opposite second end, and a central axis extending between the first end and the second end, the receiving part comprising a rod receiving portion at the first end for receiving a rod, and a head receiving portion at the second end that defines an accommodation space for interchangeably accommodating the first head of the first bone anchor or the second head of the second bone anchor;
• a pressure member positionable in the receiving part;
• and
• a locking member positionable at least partially around the head receiving portion;
• wherein when the first head or the second head is in the accommodation space, the locking member is movable from a first position where the head in the accommodation space is movable relative to the receiving part, to a second position where the head in the accommodation space is locked relative to the receiving part, and the pressure member is configured to exert additional pressure on the head in the accommodation space to lock the head relative to the receiving part;
• wherein the coupling device comprises a restraining surface configured to cooperate with the first bone anchor to restrict pivoting of the first bone anchor relative to the receiving part, and wherein the coupling device is configured to cooperate with the second bone anchor to restrict pivoting of the second bone anchor relative to the receiving part differently than the restricted pivoting of the first bone anchor relative to 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 receiving part having a first end, an opposite second end, and a central axis extending between the first end and the second end, the receiving part comprising a rod receiving portion at the first end for receiving a rod, and a head receiving portion at the second end that defines an accommodation space for accommodating the head, wherein a plurality of slits extend from the second end towards the first end to form at least one wall section configured to be separated from the rest of the receiving part to form a cutout portion configured to facilitate angulation of the bone anchor at an enlarged pivot angle in at least one direction relative to the receiving part;
• and
• a locking member configured to be assembled to the receiving part, wherein when the head is in the accommodation space, the locking member is movable from a first position where the head is movable relative to the receiving part, to a second position where the head is locked relative to the receiving part;
• wherein the coupling device comprises a restraining surface configured to cooperate with the head of the bone anchor to restrict pivoting of the bone anchor relative to the receiving part.