Measurement accuracy in acetabular cup wear

The accuracy of three methods (the simple and noncomputerized Scheier-Sandel and Charnley-Duo methods and the computerized Ein Bild Roentgen Analyse [EBRA] method) for retrospective wear measurements of the acetabular cup from standard pelvis radiographs was studied. Measurements on 13 hip prostheses were compared with those obtained by roentgen stereophotogrammetry analysis. The Scheier Sandel method had the lowest accuracy and the EBRA method had the best accuracy. The Charnley-Duo method was almost as good when starting analysis 3 months after surgery and is easier to use. The EBRA method is useful for accurate measurements on a small number of patients; the Charnley-Duo method is recommended for clinical wear studies on a larger number of patients.