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.
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. 14. The improvement of claim 13 wherein a pair of shallow grooves are formed in the outer surface of the receiver, each groove communicating with a respective aperture, each groove extending from the respective aperture to a top surface of the top portion of the receiver, each groove having a width for receiving a second manipulation tool.