An implantable device (40, 50, 80, 210, 300, 301, 400, 501, 504, 510, 520, 606, 607, 610, 620, 640, 650, 700, 800) for the adjustment of a bone in a mammal, comprising: - at least one elongated device adapted to be implanted in relation to said bone. - two or more anchoring devices (31, 32, 33, 34, 101, 102, 502, 503, 505, 506, 511, 512, 521, 522, 922, 923, 1050, 1051) adapted to be in contact with the bone in said mammal, engaging the cortical part of the bone, and - an adjustment device for adjusting at least one mechanical bone related parameter of said at least one elongated device, wherein said adjustment device is constructed to postoperatively adjust said mechanical bone related parameter, and wherein the anchoring device is adapted to be adjustable by said adjustment device, when implanted in the mammal, for engaging and stabilizing the anchoring device in relation to the bone, wherein said implantable device is adapted to be wirelessly powered, directly or indirectly, and adapted to receive wireless energy, non-invasively transmitted from an external source for adjusting said at least one mechanical bone related parameter by said adjustment device, wherein the implantable device further comprising an implantable internal energy receiver for receiving the wireless energy, the energy receiver having an internal first coil and a first electronic circuit connected to the first coil, adapted to receive the wireless energy from an external energy transmitter transmitting the wireless energy wherein the implantable device is characterized in that it comprises a feedback device for sending feedback information from inside the patient's body to the outside thereof, the feedback information being related to at least one of a physical parameter of the patient and a functional parameter related to the implantable device, wherein the feedback device is adapted to communicating out information relating to the amount of energy received in the first coil as a feedback information, allowing a second electronic circuit connected to a second coil to determine the coupling factors between the first coil and a second coil comparing the amount of transferred energy by a second coil with the feedback information related to the amount of energy received in the first coil, allowing a regulation of the transmitted energy depending on an obtained coupling factor, and wherein the implantable device further comprises implantable electrical components including at least one voltage level guard and/or at least one constant current guard. - at least one elongated device adapted to be implanted in relation to said bone. - two or more anchoring devices (31, 32, 33, 34, 101, 102, 502, 503, 505, 506, 511, 512, 521, 522, 922, 923, 1050, 1051) adapted to be in contact with the bone in said mammal, engaging the cortical part of the bone, and - an adjustment device for adjusting at least one mechanical bone related parameter of said at least one elongated device, wherein said adjustment device is constructed to postoperatively adjust said mechanical bone related parameter, and wherein the anchoring device is adapted to be adjustable by said adjustment device, when implanted in the mammal, for engaging and stabilizing the anchoring device in relation to the bone,