The Research Of Surgical Navigation System In Orthopaedics

Computer aided surgery is a multi-discipline topic that including computer technology, precision machine, mathematics, precision measurement, medicine and image engineering. Its functions are as follows: (1) helping the surgeon to diagnose patient accurately. (2) Showing instruments' exact position relative to focus, and the surgery can see the operation route and position clearly, thus reducing operation hurt and saving operation time. The common method is to use intra-medullary nail to fix the thighbone and shinbone fracture. Therefore, it is worthwhile to do research on ubiety btween operation tools and body tissue.By analyzing the present condition of domestic and foreign techniques, a new surgical navigation method that based on C-arm X-ray image is given, and the hardware and software of the surgical navigation system are developed. It helps to overcome the difficulty of interlocking intra-medullary nail's orientation in thighbone and shinbone operation. There are two methods in CCD calibration, one is linear calibration, which doesn't take lens's distortion into account, and the other is nonlinear calibration which considers lens's distortion. A new method by analyzing above two methods is given. First, calibrating the CCD in linear method, and then compensating the error. It not only reduces the error drastically in linear calibration, but also avoids the shortcoming of nonlinear calibration. In binocular matching, we advance corresponding point's matching algorithm based on epipolar line bunch, order bunch and geometrical comparability bunch, and matching two CCD markers correctly.In the analog experiment of operation navigation, according to the theory that three points can form a coordinate, we get the relative position of the drill and the intra-medullary nail with the help of C++ Builder and MATLAB, and navigate thighbone and shinbone interlocking intra-medullary nail orientation correctly.In a word, the paper aims at the difficulty of how to locate intra-medullary nail's outlying screw in fracture operation navigation, according to the method that binocular can apperceive depth, getting marker's 3-D position with the help of binocular vision technology. The system gets two image of one object with two CCD, thus obtains depth from two CCD's parallax. After investigating the operation spot and discussing with surgeons we use LED as markers, and get the marker's 3-D position with a non-contact optics orientation method. After calibrating the CCD, processing the image, the system can figure out marker's areal coordinates, get marker's 3-D coordinate in dummy world coordinate system, thereby obtain instrument's 3-D position and orientation. After the coordinate transformation and a series of orientation calculation, operation navigation comes true. It lays a foundation for the development of a surgical navigation system for practical use.