A device for regenerating a bone includes a sheathing and a swelling agent. At least a portion of the sheathing has the shape of a bellows, and/or the exterior of the sheathing bears at least one lamella. The swelling agent is enclosed by the sheathing. The sheathing is biocompatible, expandable, contractible, and/or deformable in a predefined and controlled manner as a function of a force effect induced by a change in volume of the swelling agent.
