The Repeatability of EBRA in Migration and Wear Analysis

The new computerized EBRA method should be tested for its usefulness in multicentre studies. One patient was followed with roentgen-stereophotogrammetry for three years after THA. Ten clinical pelvic radiographs were taken over a period of nine years and analysed with EBRA at four different centres independently. The maximum difference in repeated measurements after nine years was 2,2 mm for migration and 0,7 mm for wear. The error of measurement (two standard deviations) was 0,36 mm for horizontal and 0.62 mm for vertical migration. For wear it was 0,06 mm and 0,16 mm respectively. The results with EBRA were similar to the corresponding roentgen-stereophotogrammetric results. EBRA proved to be useful for multicentre studies, reducing the error of measurement. It might detect prosthetic failure at a more early stage.