13. In a bone anchor, the improvement comprising: a) a shank having a body for fixation to a bone and an integral upper substantially spherical head having a first radius; b) a receiver having a base, a first pair of upright arms and an outer surface, the receiver upright arms defining an open channel, the base defining a chamber and a lower opening, the chamber communicating with both the channel and the lower opening, each arm having a through aperture formed therein; c) an insert disposed within the receiver chamber, the insert having a surface sized and shaped for frictional mating cooperation with the shank head and having a second open channel, the insert further having a second pair of upright arms, each arm having an interior surface and each arm having an outwardly extending wing, the arm interior having a groove, the groove being engageable by a first manipulation tool for movement of the insert upward, downward, and rotationally; and d) a resilient open retainer having a base, the retainer captured within the chamber and expandable about at least a portion of the shank head and wherein expansion-only locking engagement occurs between the shank upper portion and the retainer base and between the retainer base and the receiver, the retainer having a concave second substantially spherical surface with a radius smaller than the radius of the shank head, the second surface terminating at upper and lower edges, the edges temporarily frictionally mating with the shank head, providing a friction fit between the retainer and the shank head during non-locking angular manipulation of the shank with respect to the receiver.
19. The improvement of claim 13 wherein the retainer further comprises a pair of opposed outwardly extending resilient tabs and the retainer base having at least a first planar surface and the receiver having a second planar surface partially defining the receiver chamber and a second pair of opposed apertures and wherein after the shank head is received through the retainer base, the retainer base first planar surface is seated on the receiver second surface and the resilient tabs expand to a neutral state and are captured within the second pair of receiver apertures.