An implantable device for the elongation of a bone in a mammal. The device comprises at least one elongated device adapted to be implanted in relation to said bone and two or more anchoring devices adapted to be in contact with the bone in said material, adapted to engage the bone and stabilizing in relation to the bone, wherein said anchoring devices are adapted to be implanted intramedullary in the bone of said mammal. The two or more anchoring devices are adapted to engage said bone from the inside of the intramedullar cavity of the bone and carry weight on the inside of the bone. The device further comprises an adjustment device adapted to be implanted intramedullary in the bone of said mammal, for adjusting at least one mechanical bone related parameter of said at least one elongated device, wherein said adjustment device is constructed to postoperatively non-invasively adjust said at least one mechanical bone related parameter.
