A method of navigating a cutting instrument, via a computer system, the method comprising: (a) mounting a patient-specific anatomical mapper (PAM) to a human in a single known location and orientation, where the PAM includes a surface precisely and correctly mating with a human surface correctly in only a single location and orientation； (b) mounting a reference inertial measurement unit (IMU) to the human； (c) operatively coupling a guide to the PAM, where the guide includes an instrument inertial measurement unit (IMU) and at least one of a cutting slot and a pin orifice； (d) outputting data from the reference IMU and the instrument IMU indicative of changes in position and orientation of the guide with respect to the human； (e) repositioning the guide with respect to the human to a position and an orientation consistent with a plan for carrying out at least one of a cut and pin placement； and, (f) visually displaying feedback concerning the position and orientation of the guide with respect to the human using data output from the reference IMU and the instrument IMU, which data is processed by a computer program and the computer program directs the visually displayed feedback.
