This is a new bone spacer with semispherical projecting parts and/or teeth suitable for fitting and engaging in cavities specifically prepared on the surface of the vertebrae so as to prevent the displacement of said spacer, and containing at least one channel placing the side facing towards the operator during its insertion in communication with the two opposite, superior and inferior surfaces facing the vertebrae. Plates are also provided for coupling superiorly and inferiorly to the spacer, complete with ribs and/or teeth.