Patent ID: 7789896

Claim:
A polyaxial bone screw assembly comprising: a) a receiver defining a central bore and having a top portion and a bottom portion, the bottom portion defining a first recess communicating with the central bore and having a bottom opening, the bottom opening having a diameter; b) a shank having an upper portion and a lower portion for fixation to a bone, the upper portion having an upper surface and a maximum width smaller than the receiver bottom opening diameter; the shank upper portion including a radially outward extending stop that is sized and shaped to pass through the receiver bottom opening; the shank upper portion having a second recess on the upper surface thereof that is sized and shaped to receive a tool for operably rotating the shank for installation and removal; c) an independent retaining and articulating structure mateable with the shank upper portion, the retaining and articulating structure having a contact surface configured for slidable engagement with the receiver at the bottom portion defining the recess; the retaining and articulating structure having a top surface; the shank stop operably positioning the retaining and articulating structure on the shank and having a lower surface that cooperates with the retaining and articulating structure contact surface to slidably engage the receiver; d) a compression structure insertable in the receiver and pressable exclusively against the retaining and articulating structure; and e) the shank, the retaining and articulating structure and the receiver being joinable into a pre installation unit prior to installation into a patient wherein, after the shank and the retaining and articulating structure are joined in the receiver, the shank tool receiving second recess on the shank is accessible to such a tool to allow implantation of the shank into a patient's bone while the shank is part of the unit.