The disc has an intermediate body comprising a sliding surface of a revolution shape around to a point. A connecting unit connects the intermediate body with a plate, so that the intermediate body is comprised inside a space defined by plans passing respectively by four faces of two couple lateral faces (24, 26). Another plate comprises a contact surface that contacts with a vertebra and comprises another sliding surface of revolution shape around the point. The plates are associated, such that sliding surfaces cooperate with each other by sliding in rotation.
