Method of assembling a cannulated polyaxial screw having a shank head with a flat top spaced apart from a compression insert

A method of assembling a cannulated polyaxial bone anchor into a bone of a patient with tooling and connecting to a rod, the method comprising:

• obtaining a cannulated screw shank comprising an upper capture portion, an anchor portion opposite the upper capture portion configured for implantation into the bone, and a central bore extending an entire length of the cannulated screw shank from an internal drive socket to a distal tip of the anchor portion, the internal drive socket entirely surrounded by a planar annular top surface;
• obtaining a receiver comprising a pair of arms extending upwards from a base to define an open channel extending between front and back faces of the receiver that are defined in part by opposed parallel front and back planar surfaces on the arms, a tool engagement recess formed into an outer side surface of each of the pair of arms, the base including an internal accommodation space communicating with the open channel and with a bottom opening to define an axial bore centered about a vertical centerline axis of the receiver, the internal accommodation space including a non-tapered seating surface adjacent the bottom opening;
• obtaining a compression insert having a lower surface configured to engage the upper capture portion of the cannulated screw shank and an upper surface configured to engage the rod;
• positioning the cannulated screw shank within the internal accommodation space with the upper capture portion in engagement with the non-tapered seating surface and the compression insert at least partially in the open channel with the lower surface in engagement with the upper capture portion;
• implanting the anchor portion of the cannulated screw shank into the bone of the patient with the tooling attached to the tool engagement recesses of the receiver and without a closure top in the open channel of the receiver;
• positioning a rod in the open channel of the receiver with an outer cylindrical surface on the rod in engagement with the upper surface of the compression insert;
• and
• rotatably downwardly positioning the closure top into the open channel of the receiver above the rod to lock the rod to the cannulated polyaxial bone anchor,
• wherein with the cannulated polyaxial bone anchor in a locked configuration, the planar annular top surface of the upper capture portion is spaced apart from the lower surface of the compression insert.