High Accuracy of Pelvic Tilt Measurement Using Three-Dimensional Planning Software: A Validation Study Using Dry Bone Models

The “CR Alignment” function was recently introduced in ZedHip®, the hip joint module of ZedView®, to evaluate pelvic tilt in non-supine positions via two-dimensional (2D)‒3D matching using radiographs. However, its ccuracy has not been validated. This study therefore evaluated the accuracy of pelvic tilt measurements using the CR Alignment function in dry pelvic bone specimens. Two cadaveric pelvic bone models were placed in nine orientations (anterior/posterior tilt and left/right rotation). Both radiographic and CT images were acquired in each position. In Study 1, pelvic tilt measured directly from CT images was defined as the “true value.” Three observers used the CR Alignment function to calculate pelvic tilt on radiographs, and measurement errors were determined relative to the true values. In Study 2, measurement errors were compared between matched (same position) and mismatched (different position) imaging. In Study 1, the mean measurement error was 1.28±0.64°. Intra- and interobserver intraclass correlation coefficients were 0.996-0.998 and 0.997, respectively. In Study 2, the mean errors were 1.20±0.88° (matched) and 1.32±1.03° (mismatched). This software exhibited high accuracy and reproducibility in 2D‒3D matching of pelvic tilt, with lower variability under matched acquisition, demonstrating its utility for pre- and postoperative assessment in joint arthroplasty.