Monitoring Implant Migration in Total Ankle Arthroplasty: A Longitudinal Study using Weight Bearing CT based Radio Stereometric Analysis

Research Type: Level 4 – Case series Introduction/Purpose: Radiostereometric analysis (RSA) is the gold standard for detecting in vivo implant migration, a key indicator of implant stability in Total Ankle Arthroplasty (TAA). However, conventional RSA is practically cumbersome, and access is limited, while Weight Bearing CT (WBCT) could be harnessed to perform Computed tomography-based RSA (CT-RSA). This pilot study aims to describe and validate WBCT-based Volumetric Matching Micromotion Analysis (V3MA), an innovative CT-RSA technique, in the setting of TAA to investigate migration patterns in TAA implants. Methods: This retrospective analysis included ten patients with Salto fixed bearing implants. Each patient had two WBCT scans acquired at minimum six months postoperatively for the first and minimum two years subsequently for the second. Scans were analyzed using V3MA software following segmentation in Mimics. Prosthesis migration (translation and rotation) was quantified in three dimensions. Metrics included translation (mm) and rotation (°). Outlier cases were scrutinized for artifacts or atypical movement. Descriptive analyses were visualized with boxplots and tables; no inferential statistics were performed due to sample size constraints. Results: Median translation values were stable for both tibial (0.11 mm; range 0.08–0.47 mm) and talar (0.10 mm; range 0.03–0.39 mm) components. Rotational movement showed median values of 0.35° for tibial and 0.39° for talar components. Outlier analysis identified one patient with significant deviations attributed to a motion artifact. Conclusion: CT-RSA using V3MA and WBCT scans was feasible for monitoring TAA implants, demonstrating stable migration measurements comparable to established RSA standards. Motion artifacts could present potential limitations, recommending adoption of positional guidelines into standard clinical workflows. Further research is needed to assess the clinical benefits of WBCT over conventional CT and to evaluate early postoperative migration patterns and risk factors. Implementing these methodological optimizations may substantially improve the practicality and clinical utility of CT-RSA in the longitudinal assessment of ankle prosthesis stability, enhancing postoperative surveillance and clinical decision-making in ankle arthroplasty.