Patent ID: 8257399

Claim:
An anchoring assembly for anchoring a rod to a bone or a vertebra, the anchoring assembly comprising: a bone anchoring device comprising: a shaft; and a head connected to said shaft and having a recess with a base having a contact surface, the head further comprising two substantially vertically extending legs spaced apart by a first distance and defining a channel; a fixation element having a contact surface facing the contact surface of the base of the head, the fixation element secured to the legs and configured to move sufficiently into and out of the channel; and at least a first rod and a second rod having different diameters and configured to be interchangeably received in the channel and to be clamped by the fixation element; wherein when any one of the rods is received in the channel, the contact surface of the fixation element and the contact surface of the base contact the rod to clamp the rod in the channel; wherein the first rod and the second rod each have diameters within a range that is smaller than the first distance and sufficiently sized so as to be spaced apart from a bottom of the contact surface of the base when clamped in the channel; and wherein for all rods having a diameter within the range, the rod contacts the contact surface of the base only along two contact lines.