An implantable device comprising a driving unit and a kinematic assembly joined together: the driving includes, in an hermetic capsule, electromechanical component, like an electric motor and, the battery pack, and electronic elements, while the kinematic assembly includes a reducer and an actuator, for example a lead-screw distractor, and is lubricated by body fluids. Mechanical energy is transmitted without contact from the former to the latter by a magnetic transmission.