EBRA improves the accuracy of radiographic analysis of acetabular cup migration.

EBRA (Ein Bild Röntgen Analyse) is a new computerized method measuring migration and wear of the acetabular cup, suggested to improve measurement accuracy. We evaluated possible errors of measurement and compared EBRA with standard methods. 1. We did repeated measurements on a single radiograph using the same reference lines. The reliability of the input procedure with standard measurements was significantly better than repeated digitization with EBRA. 2. In a more clinical test, a group of 10 patients was studied. 5 radiographs were taken of the same patient on the same day. EBRA improved the reliability of repeated radiographic examination significantly for migration measurements in the vertical direction. 3. To assess the inter- and intraobserver variations, repeated measurements were performed on the clinical series of pelvic radiographs of 10 patients. EBRA was significantly better than standard methods. With EBRA, errors of wear and migration measurements could be reduced, as compared to standard methods. The major improvement with EBRA was found for migration measurements in the vertical direction.