A device for bone adjustment in a mammal. The device comprising two or more anchoring devices adapted to implanted intramedullary and attached to a bone in said mammal and an adjustment device for exerting force on said anchoring devices, said adjustment device being adapted to postoperatively adjust at least one of the distance between or orientation of, at least two of said anchoring devices. The operation device further comprises a motor and said operation device is adapted to operate said adjustment device. The operation device further comprises a gearbox connected to the motor, wherein an outgoing speed from the gear box is lower than the speed by the motor alone, accomplished by the gearbox, and wherein the outgoing speed of the gearbox is less than 10 turn per second during normal operation. The device also comprises a control device adapted to control the operation device, wherein the control device is: programmed to control the device according to a pre-programmed time-schedule, and programmed to control the device based on input from a sensor or measuring device sensing any possible physical parameter of the patient or any functional parameter of the system.
