Adjustable implant and method of use

A method of adjusting an adjustable implant configured for implantation internally within a subject, the adjustable implant comprising a housing, a permanent magnet disposed within the housing and configured for rotation about an axis of rotation, the permanent magnet operatively coupled to a drive transmission disposed within the housing and configured to alter an external dimension of the adjustable implant, wherein the drive transmission comprises a lead screw operatively coupled to the permanent magnet of the adjustable implant and a nut moveable along the length of the lead screw, wherein the adjustable implant is configured to be adjusted using a programmable external adjustment device comprising drive control circuitry, a motor, and at least one permanent magnet configured for rotational movement in response to actuation of the motor, wherein the drive control circuitry is configured to receive and store drive instructions, the method comprising:

• adjusting the implant in accordance with the drive instructions stored in the drive control circuitry of the external adjustment device, wherein the drive control circuitry is configured to receive an input signal from an encoder disposed external to the subject in the external adjustment device that measures the angular position of the at least one permanent magnet of the external adjustment device and terminates operation of the motor based at least in part on the input signal from the encoder.