The system has an anchoring element (20) e.g. slug or screw, with a cylindrical head connected to a rod. A cylindrical shaped housing is realized such that a longitudinal axis of the rod forms a non-zero angle with a support face (12) of a cage (10) e.g. intervertebral cage, when the head is inserted in the housing. The rod crosses the housing via an outlet port and the head via a radial groove of the housing and enters in the osseous body of one of two adjacent vertebrae (V1, V2) that is in contact with another support face (11) of the cage when cage is interposed between the vertebrae. An independent claim is also included for a positioner for placing a slug in a body of vertebrae.
