The implant includes two side walls resting against the vertebral end-plates and an intermediate wall joining the supporting walls. The implant can be deformed for insertion between the vertebrae to be treated to restore the attenuated mobility of the vertebrae, and includes mounting elements mounting on the vertebrae. The side walls have a curved shape, whose convexity is oriented towards the outside of the implant; the intermediate wall has a curved shape, whose convexity is oriented towards the outside of the implant such that it does not form any pronounced angles with the supporting side walls. The supporting side walls and the intermediate wall, have a partially oval shape; and the mounting elements are configured such that the implant can be mounted on the vertebrae.