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

A method for coupling a rod to a bone using a 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 rod receiving portion for receiving a rod, a head receiving portion for interchangeably receiving the first head of the first bone anchor or the second head of the second bone anchor, and a central axis that extends through the rod receiving portion and the head receiving portion, and a pressure member configured to exert pressure on the first or second head when the first or second head is in the receiving part to clamp the first or second head at a particular position relative to the receiving part, and a fixation device, the method comprising:

• selecting the first bone anchor or the second bone anchor to assemble to the coupling device, 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 to a single plane that includes the central axis, 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;
• implanting the selected bone anchor in bone;
• adjusting the coupling device to a desired position;
• inserting the rod into a recess of the rod receiving portion of the receiving part;
• and
• advancing the fixation device into the rod receiving portion to lock the rod and the head of the selected bone anchor relative to the coupling device.

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 with a free end defining a recess for a tool;
• a second bone anchor different from the first bone anchor and comprising a second shank for anchoring to bone and a second head with a free end defining a recess for a tool;
• and
• a coupling device comprising:
• a receiving part having a rod receiving portion for receiving a rod, a head receiving portion for interchangeably receiving the first head of the first bone anchor or the second head of the second bone anchor, and a central axis that extends through the rod receiving portion and the head receiving portion;
• and
• a pressure member configured to exert pressure on the first or second head when the first or second head is in the receiving part to clamp the first or second head at a particular position relative to the receiving part;
• wherein the coupling device comprises a restraining surface configured to cooperate with the first bone anchor to prevent the first bone anchor from pivoting away from the central axis of the receiving part in every radial direction, and wherein the coupling device is configured to cooperate with the second bone anchor to facilitate pivoting of the second bone anchor away from the central axis of the receiving part.