Surgical instrument including housing, a cutting accessory that extends from the housing and actuators that establish the position of the cutting accessory relative to the housing

A system including an instrument adapted to be manually supported and moved by a user. The instrument having a hand-held portion, a working portion movably coupled to the hand-held portion, and a plurality of actuators operatively coupled to the working portion for moving the working portion in a plurality of degrees of freedom relative to the hand-held portion. The instrument having a tracking device attached to the hand-held portion. The system including a navigation system for determining a position of the working portion relative to a target volume, and a control system in communication with the actuators to control the actuators to move the working portion relative to the hand-held portion such that the working portion autonomously follows a path defined in the control system to remove material of the target volume while the user maintains the hand-held portion in a gross position relative to the target volume.