2025 ISAKOS Biennial Congress ePoster
Operator variation in applying the AtMoves knee loading device for evaluation of tibial component loosening
George Samuel Buijs, MD, Amsterdam NETHERLANDS
Maaike Annemiek ter Wee, MSc, Amsterdam NETHERLANDS
Chiel Klein, BSc, Amsterdam NETHERLANDS
Lidwine B. Mokkink, PhD, Amsterdam NETHERLANDS
Johannes Dobbe, PhD, Amsterdam, Noord-Holland NETHERLANDS
Mario Maas, MD, PhD, Amsterdam NETHERLANDS
Matthias U. Schafroth, MD, Nigtevecht, Noord-Holland NETHERLANDS
Geert Streekstra, PhD, Amsterdam, Noord-Holland NETHERLANDS
Leendert Blankevoort, PhD, Amsterdam NETHERLANDS
Arthur Johan Kievit, MD, Weesp NETHERLANDS
Amsterdam University Medical Center, University of Amsterdam, Amsterdam, NETHERLANDS
The FDA has not cleared the following pharmaceuticals and/or medical device for the use described in this presentation. The following pharmaceuticals and/or medical device are being discussed for an off-label use: AtMoves, AtMoves Knee System
Summary
This study evaluated operator variance for the AtMoves Knee System loading device in patients and found that it can be used consistently by different trained operators with negligible differences in the measurement of tibial component motion relative to the bone.
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Abstract
Background
The current diagnosis of aseptic knee arthroplasty loosening lacks standardization and a definitive test. The AtMoves Knee System offers a direct, CT-based approach to diagnose aseptic loosening by applying a bending moment to the knee by means of a loading device and quantifying the tibial component displacement relative to the tibia by processing the CT scans. This study aims to evaluate the impact of operator differences when applying the AtMoves Knee System’s loading device for detecting implant loosening.
Methods
This study evaluated 16 subjects from a clinical follow-up study, who underwent repeated CT examination with valgus and varus loading using the AtMoves Knee System. Two operators applied the loading device subsequently to each patient. 3D CT image analysis quantified tibial component displacement parameters i.e. rotation about the screw-axis, Maximum Total Point Motion (MTPM) and mean Target Registration Error (mTRE). Two analysis protocols were employed: one including the entire tibia (100%) and another using the proximal tibia (20%) as reference. The purpose of the latter was to mitigate the impact of tibia deformation under load. These protocols were used to evaluate operator variation using the intraclass correlation coefficient (ICCagreement) and measurement error by calculating the standard error of measurement (SEM), standard error of operator (SEO) and smallest detectable change (SDC).
Results
The 100% tibia protocol showed moderate to good ICCagreement for MTPM (0.81), mTRE (0.84), and rotation about the screw-axis (0.64), with SEMs of 0.15 mm, 0.10 mm, and 0.16°, respectively. SEO’s were both statistically and clinically negligible. The corresponding SDC values were 0.44˚ screw-axis rotation, 0.41 mm MTPM and 0.27 mm mTRE. The 20% tibia protocol showed smaller SEM, SEO and SDC values compared to 100% tibia analysis, with poor ICCagreement explained by reduction in patient variance because of tibia deformation correction and the homogenous subject group.
Conclusion
The AtMoves Knee System loading device can be operated by different trained operators and is associated with negligible inter-operator differences of the parameters describing the load-induced motion of the tibial component of the total knee arthroplasty.