Vertebral anchoring device and its blocking device on a polyaxial screw

The vertebral anchoring device according to the present invention comprises a connector (2), a connecting rod (10) and a polyaxial anchoring screw (3) comprising a spherical head (15) and a screw-threaded body (16) whose external diameter d at a summit of the screw threads (17) is greater than the external diameter a of the spherical head (15), each connector (2) being constituted by a connecting element (4) comprising vertical branches (5, 6) delimiting an opening (7) of U shape, and by a locking clip (8) provided with a pressure screw (9) for blocking in the bottom of the U the connecting rod (10), said connecting element (4) being pierced at its middle with a vertical bore (11) permitting receiving opposite the opening (7) a blocking device (19) formed by a ring (20) and a screw-threaded socket (21) for the emplacement and positioning of the connector (2) on the spherical head (15) of the anchoring screw (3).