Abstract: The invention relates to an implant for an osteosynthesis device, in particular for the spine, the implant including a first assembly itself including: a fixing body having a housing for receiving the head of an anchor screw in such a manner as to define a ball joint; and a positioning ring; and a second assembly itself including a nut type system. According to the invention: the first assembly has a positioning ring mounted in the fixing body; and the second assembly has a nut type system, adapted, when tightened on the body, to bear against the bracing rod and to cause the positioning ring to move in linear displacement.