Digital automated RSA compared to manually operated RSA

The accuracy of digital Roentgen stereophotogrammetric analysis (RSA) was c ompared to the accuracy of a manually operated RSA system. For this purpose , we used radiographs of a phantom and radiographs of patients. The radiogr aphs of the patients consisted of double examinations of 12 patients that h ad a tibial osteotomy and of double examinations of 12 patients that receiv ed a total hip prosthesis. First, the radiographs were measured manually wi th an accurate measurement table. Subsequently, the images were digitized b y a film scanner at 150 DPI and 300 DPI resolutions and analyzed with the R SA-CMS software. In the phantom experiment, the manually operated system pr oduced significantly better results than the digital system, although the m aximum difference between the median values of the manually operated system and the digital system was as low as 0.013 mm for translations and 0.033 d egrees for rotations. In the radiographs of the patients, the manually oper ated system and the digital system produced equally accurate results: no si gnificant differences in translations and rotations were found. We conclude that digital RSA is an accurate, fast, and user friendly alternative for m anually operated RSA. Currently, digital RSA systems are being used in a gr owing number of clinical RSA-studies. (C) 2000 Elsevier Science Ltd. All ri ghts reserved.