Reliability analysis of WBCT-derived 3D models for comparing preoperative and postoperative alignment in total ankle arthroplasty

Background: Traditional imaging techniques for total ankle arthroplasty (TAA) evaluation are limited by rotational bias and bone superimposition, highlighting the necessity for more precise assessment methods. The advent of weight-bearing computed tomography (WBCT) generated 3D enhance the visualization of foot and ankle alignment, offering unmatched detail. This study aims to assess the accuracy of preoperative and postoperative measurements in TAA across all three planes using WBCT-generated 3D models. We hypothesize that these models can be reliably used to compare preoperative and postoperative alignment. Methods: For 81 patients undergoing TAA, preoperative and postoperative WBCT models were created. Measurements included five coronal angles: Alpha, Tibiotalar Surface Angle (TSA), Talar Tilt Angle (TT), Salzmann's 20 degrees Angle (SA), and Talocalcaneal Angle (TCA); three sagittal angles: Beta, Gamma, and Tibiotalar Ratio (TTR); and one axial angle: The Posterior Talar Rotational Angle (PTARA). Two raters evaluated these before and after surgery in two separate sessions. The study then compared preoperative to postoperative measurements, calculating inter-rater and intra-rater reliability. Results: Significant changes were observed in three coronal angles (TSA, TT, and SA) and two sagittal angles (Beta and Gamma), with P-values of 0.2, 0.007, 0.019, <0.001, and <0.001, respectively. No significant changes were noted in Alpha, TCA, TTR, and PTARA, with P-values of 0.2, 0.9, 0.2, and 0.6, respectively. Intra-rater and inter-rater reliability scores ranged from 0.885 to 0.97, indicating good to excellent interclass correlation across all planes, both pre-and postoperatively. Conclusion: WBCT-generated 3D modeling and image analysis software have enabled a detailed comparison between preoperative alignment and postoperative TAA positioning across coronal, sagittal, and axial planes, revealing significant adjustments in coronal and sagittal alignments. The high reliability and reproducibility of these measurements affirm their value in preoperative planning in improving the accuracy of surgical interventions.