Modular polyaxial bone anchor with retainer having interconnected pieces

摘要

A polyaxial bone screw assembly includes a threaded shank body having an integral upper portion receivable in a one-piece receiver, the receiver having an upper channel for receiving a longitudinal connecting member and a lower cavity cooperating with a lower opening. A down-loadable, friction fit compression insert (some with lock and release feature), a down-loadable two-piece, interconnected retaining ring articulatable with respect to the receiver and an up-loadable shank upper portion cooperate to provide for assembly of the shank with the receiver either prior to or after implantation of the shank into a vertebra.