Clinical Validation and Excellent Interobserver Agreement of Volumetric Matching Micromotion Analysis (V3MA) in Total Knee Arthroplasty.

CT-based radiostereometric analysis (CT-RSA) is an alternative to RSA to measure implant migration. We performed a clinical validation study using VoluMetric Matching Micromotion Analysis (V3MA) software for CT-RSA. The aims of this study were to assess the agreement between V3MA and Model-based RSA software (for RSA), and to determine the interobserver agreement in V3MA. On a subset of patients included in a clinical trial, knee prosthesis tibial implant migration was measured between 1 and 5 years postoperative with V3MA and Model-based RSA software. V3MA and Model-based RSA results were compared by assessing the mean differences and limits of agreement (mean ± 1.96* standard deviation) using Bland-Altman analysis. V3MA migration results of two observers were compared using intraclass correlation (ICC) and Bland-Altman analysis. Twenty-four patients were included in the analysis. The mean difference (limits of agreement [LOA]) was -0.14 mm [-0.88 to 0.60] for maximum total point motion (MTPM). LOA for translations and rotations did not exceed ±0.5 mm and ±1°, respectively. The ICC (95% confidence interval) for MTPM between observers was 0.995 (0.989-0.998), and the mean difference [LOA] was 0.04 mm [-0.17 to 0.24]. We showed that between 1 and 5 years postoperative, V3MA migration results were comparable to those of Model-based RSA for cemented tibial component migration in a clinical study. The interobserver variability showed excellent agreement for V3MA. Overall, V3MA is a valid alternative to Model-based RSA for the analysis of tibial component migration in TKA with medium-term follow-up.