Abstract: The device includes at least one pin and parts for anchoring this pin to the vertebrae. The device includes spherical rings having a plurality of slots distributed on their peripheries. The head of each anchoring part has a cavity that may receive one of the rings with snap-on installation, and at least two lateral threaded holes. Each anchoring part includes a clamping ring presenting a central aperture in a conical form allowing the clamping ring to come into contact with the ring during tightening of the screws that are within the clamping ring.