A position monitoring system comprises a single composite fiducial reference comprised of a fiducial key and a fiducial extension rigidly and removably attached to the fiducial key, a tracker for obtaining image information of the surgical site, and a computer system with processor, memory, a software program, and access to a database. The computer has scan data of an area of a surgical patient with the fiducial reference fixed to the area by a multipodal surgical screw fixture. A uniquely identifiable first marker is attached to the fiducial key in a predetermined fixed relative position and orientation. The computer determines the relative position and orientation of the marker based on live image information from the tracker, relates and displays the current position and orientation of the composite fiducial reference to the scan data during a surgical procedure. Further implements at the surgical site may bear further markers that may be tracked. The marker may also serve as fiducial extension, to which end it may be uniquely shaped or marked.
