Patent ID: 8366753

Claim:
A polyaxial bone screw assembly comprising: a) a bone screw shank having an upper portion with a capture structure having a lower convex partially spherically shaped first surface; b) a receiver having a pair of arms forming a channel, the receiver also having a cavity with a concave partially spherically shaped second surface adapted to receive and allow pivotal movement of the shank first surface during positioning and an opening to an exterior of the receiver opposite the pair of arms, the cavity communicating with the channel, the bone screw upper portion being uploaded and received in the cavity through the opening; the receiver having a lower groove within the cavity; c) a retaining structure being receivable in the cavity and securable to the receiver in fixed relation thereto when the shank upper portion is in the receiver, the retaining structure being outwardly biased and received in the receiver lower groove; the retaining structure having a third surface sized and shaped to receive a portion of the shank first surface, the retaining structure being sized and shaped to retain the shank upper portion within the receiver cavity, the shank upper portion sized and shaped to extend above the retaining structure and receive direct downward force from direct forceful engaging contact between the rod and the shank when the shank upper portion is retained in the cavity by the retaining structure such that all downward force from the rod is applied directly to the shank and so as to lock the angular position of the receiver relative to the shank in a locked position due to the direct forceful contact between the rod and the shank, the assembly having an unlocked position wherein the shank upper portion is in sliding, pivotable relation with the retaining structure and a locked position wherein the shank first surface is in direct frictional engagement with the receiver second surface and the retaining structure third surface; and d) the second surface of the receiver and the third surface of the retainer cooperating to receive the first surface of the shank capture structure to allow polyaxial rotation of the shank relative to the receiver in the unlocked configuration during assembly.