Accuracy and reliability of different methods to evaluate the acetabular cup version from plain radiographs

Abstract

Purpose: The purpose of this study was to compare different methods of evaluating the version of a metallic acetabular cup from plain radiographs and to compare them regarding their accuracy, inter- and intra-observer reliability.

Methods: Conventional anterior-posterior radiographs were taken of a phantom-model at different defined ante- and retroversion angles of the acetabular cup. The version angles of the acetabular cup were derived according to four different established methods from the radiographs by five independent examiners.

Results: We were able to determine the radiographic version with the greatest accuracy according to a modified technique of Pettersson et al. Furthermore, we found the highest intra- and inter-observer reliability using this technique.

Conclusions: A modified technique of Pettersson et al. broadens the spectrum of applicability for the radiographic evaluation of the version angle of metal-backed acetabular cups in comparison to the originally introduced method. In clinical practice, however, the significance of deriving the cup position from standard radiographs should not be over-estimated and therefore a computed tomography should be performed in certain critical cases.