Accuracy of Planar Anteversion Measurements in Anteroposterior Radiographs

Abstract

Introduction Number of methods has been suggested to measure anteversion in the simple AP radiograph and a few studies have validated their accuracy and reliability. In the current study, we compared six widely used anteversion measurement methods using two different radiographs (conventional pelvis AP vs hip centered AP) in order to determine which measurement method and which radiograph provides highest accuracy and reliability. Material and methods We developed custom made two planar anteversion measurement models for the validation. Each models are designed for Pelvis AP and hip AP. The radiographs were taken with the both models’ inclination changing from 10° to 70° at 10° increments and for each inclination angles, anteversion was changed from 0° to 30° at 5° increments. Therefore, the x-ray of the two models were taken in 49 scenarios. The measurements were done independently by two orthopaedic surgeons blinded from each other using 6 methods : 1) Pradhan et al, 2) Lewinak et al, 3) Widmer et al, and 4) Liaw et al. 5) Hassan et al, 6) Ackland et al. Result The highest accuracy was found when Liaw method was used in hip centered AP radiograph which showed difference of 1.37° ± 1.73. Also, regardless of the type of the radiographs, Pradhan, Lewinnek, Liaw all showed relatively high accuracy. However, substantial difference was found when Widmer, Hassan, Ackland method were utilized regardless of the type of radiograph used. When the anteversion were measured in the inclination between 30° and 50°, Pradhan’s method in pelvis AP showed the highest accuracy (1.23° ± 0.92°). Also, we found no significant difference when measured anteversions were compared between Pelvis AP and hip centered AP. Conclusion The study indicates that the Pradhan, Liaw and Lewinnek method may provide the relatively accurate anteversion measurement regardless of the type of the radiographs. Also, it would be unnecessary to take the hip centered AP radiographs in addition to the pelvis AP radiographs for the purpose of measuring anteversion.