Abstract

1. Abstract [Background] Orientation of acetabulum and wearing parameters are important prognostic factors after total hip arthroplasty. Various methods are proposed to measure them. All these methods need a standardized radiograph to verify their accuracy. In the past, mechanical devices are used. The disadvantages are expensiveness and operation error. We developed a program to do the same job. With this program, every parameter can be manipulated, and the results are reproducible without operation error. [Methods] With Windows plateform and Borland C++ builder tool, we developed the simulator. Ray tracing method is used to estimate the thickness of metal which the X-ray bean passed through. Then the photo-density is calculated by interpolation of look up tables. Parameters that we can manipulate include thickness, cup size, head size, inclination, anatomic anteversion, radiographic anteversion, and operative anteversion. [Results] With this program, we simulated 45 X-rays with different inclinations and anteversions. These simulated radiographs are printed in papers as teaching materials for practicing measurement of anteversions and wearings. The quality is as good as real X-rays, in which the real orientations and wearing are hard to estimate. We also use these simulated X-rays as source of automatic wearing measurement program. The result shows that the errors are within one millimeter. [Conclusions] Mechanical simulation is straightforward but expensive, with inevitable operation error. Computer simulated radiograph could be a standard to estimate accuracy of a new method and also serving as a training material for residents. Introduction Many parameters can (should) be measured. a. Orientations: Anteversion: Lewinnek method Liaw method Widmer method Fabeck method Inclination b. Wearing: Upper, Medial, Posterior Manual method Livermore method … Computerized method Hardinge method Shaver method Liaw method Verification of these methods is important!! Mechanical Simulation SIC03-P012 Simulated Radiograph of Total Hip Arthroplasty for Verifying Measuring InstrumentChen-Kun Liaw1,3 Rong-Sen Yang2 Sheng-Mou Hou2 Chiou-Shann Fuh3 Tai-Yin Wu4En Chu Kong Hospital, Taipei Hsian, Taiwan1National Taiwan University Hospital, Taipei, Taiwan2 National Taiwan University, Computer Science and Information Engineering3Taipei City Hospital4 • Advantages: • Easy to persuade people to use. • Disadvantages • Expensive • Precision? • Digitalization Our Solution • Building our own software • Cost down • Digitalization • Bias elimination • Batch processing can automatically produce many simulated X-rays. • Our Algorithm • Ray tracing • See X-ray as many X-ray lines • Trace every X-ray line • Calculate the total thickness of metal it passes. • Convert thickness to gray-scale pixel