| CPC A61B 17/7035 (2013.01) [A61B 17/7032 (2013.01); A61B 17/7034 (2013.01)] | 18 Claims |

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1. A method of bone fixation, the method comprising steps of:
implanting a bone anchor having a head into a bone;
attaching an anchor subassembly onto the bone anchor, the attaching step comprising:
receiving the head of the bone anchor into a lower opening of a body of the anchor subassembly, the body having an upper end defining an upper opening, and a lower end spaced from the upper end, the lower end defining a lower opening, and the body defining a bore that extends substantially between the upper opening and the lower opening; and
receiving the head of the bone anchor into an interior cavity of an insert member disposed in the bore of the body such that a lower end portion of the insert member expands so as to receive the head such that the insert member engages the head, wherein at least one slot is defined by the insert member extending from the lower end portion towards an upper end portion of the insert member so that the lower end portion expands and collapses when the head is received so that the head is inserted into the interior cavity and locked in the interior cavity;
positioning a spinal rod in a first rod-receiving channel defined by the body of the anchor subassembly and in a second rod receiving channel defined by a sleeve disposed in the bore of the body, the sleeve including at least one arm that extends along a longitudinal axis of the bore and defines a portion of the second rod-receiving channel, and the sleeve engaging the upper end portion; and
displacing the sleeve, with at least one movable element that moves along the longitudinal axis from a first position to a second position, within the bore towards the lower opening of the body such that the sleeve moves the insert member within the bore from an unlocked position to a locked position when the head of the bone anchor is disposed in the interior cavity of the insert member,
wherein in the unlocked position, the bone anchor is poly-axially rotatable with respect to the body, and in the locked position, the insert member secures a position of the bone anchor with respect to the body by engaging the head of the bone anchor.
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