Reliability and validity of a mobile application for femoral anteversion measurement in adult patients

BACKGROUND: Femoral torsion is primarily measured by computed tomography (CT), which has cost and radiation exposure concerns. Recently, femoral anteversion measurement by a simple radiograph-based mobile application was developed for patients with cerebral palsy. This study aimed to validate the use of a mobile application that can reconstruct a three-dimensional model of the femur from conventional radiographs for adults. METHODS: Medical records of 76 patients undergoing conventional femur anteroposterior/lateral radiography and femur CT were reviewed. To measure femoral anteversion on the reconstructed 3-dimensional images from both the mobile application and CT, we drew a line which connects the posterior margins of each femoral condyle and another line which passes through the center of the femoral head and the midpoint of the femoral neck. After the reliability test, a single examiner measured femoral anteversion on the mobile application and CT. Pearson’s correlation analysis was used to assess the correlation between anteversion on the mobile application and CT. RESULTS: Femoral anteversion measured on both CT and the mobile application showed excellent reliability (intraclass correlation coefficients: 0.808–0.910). The correlation coefficient between femoral anteversion measured using CT and the mobile application was 0.933 (p < 0.001). The correlation of femoral anteversion between CT and the mobile application was relatively higher in the absence of metallic implants (correlation coefficient: 0.963, p < 0.001) than in the presence of metallic implants (correlation coefficient: 0.878, p < 0.001). CONCLUSIONS: Using two simple radiographs, the mobile application showed excellent validity and reliability for femoral anteversion measurement in adults as compared to CT. With the high accessibility and cost-effectiveness of this mobile application, femoral torsion measurement might be easily performed with simple radiography in clinical settings in the near future. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13018-023-03853-y.