The present invention is an improved system for allowing an orthopaedic surgeon to safely determine the precise trajectory of insertion of a guide pin or screw into an object bone and to check the accuracy of the procedure using real time feedback. The system uses a C-arm fluoroscope in conjunction with a three-dimensional optical digitizer to provide a real time image of the drill and object bone on a screen. The system uses light emitting diodes (LEDs) positioned on the C-arm fluoroscope and on the drill and two dimensional image registration of the object bone to orientate the surgeon. In addition, LEDs are attached to a reference bar positioned on the object bone. The distinctive pattern formed by the combination of these elements allows the surgeon to continually observe the progress of the surgery without necessitating additional x-ray images. A computer software program allows the surgeon to record the position of the object bone, to correct the parallax of the C-arm fluoroscope and to relate the position of the object bone in the two fields by two dimensional image registration to determine the exact relative position of the object bone seen on the two images.