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...http://www.google.com.au/patents/US5772594?utm_source=gb-gplus-sharePatent US5772594 - Fluoroscopic image guided orthopaedic surgery system with intraoperative registration 
