Abstract: The present invention provides a MEMS sensor guidance system mounted on a surgical instrument and uses the MEMS sensor to determine Inertial Measurement Units to track rotation and acceleration in all three spatial directions. Further the invention provides a method of surgery in which a reference axis, a loci, and a depth are defined and the instrument including the sensor cluster of the invention is placed in relation to the y-axis and x-axis and following the working end is aligned and the orientation and depth data display is observed to aid in maintaining the desired instrument.