A polyaxial bone screw assembly includes a shank body having an upper head portion with a mating segment and a first partial spherical surface, a retainer structure being mateable with the mating segment of the upper head portion, the retainer structure having a second partial spherical surface such that when mated, the first and second partial spherical surfaces form a spherical ball member, a receiver defining an open channel and having a base with a seating surface partially defining a cavity with a shaped wall, the open channel communicating with the cavity, the cavity communicating with an exterior of the base through an opening sized and shaped to receive the shank upper head portion therethrough, and a bushing sized and shaped to fit within open channel and cavity and lock in recesses on interior of receiver.
