2025 ISAKOS Biennial Congress ePoster
Validation Of A Six Degrees Of Freedom Biomechanical Simulator For The Assessment Of Knee Joint Kinematics
Adrian Deichsel, MD, Münster, NRW GERMANY
Nina Marx, cand. med., Münster, NRW GERMANY
Matthias Klimek, M. Sc., Muenster GERMANY
Michael J. Raschke, MD, Prof., Münster GERMANY
Christian Peez, MD, Münster, NRW GERMANY
Thorben Briese, MD, Münster GERMANY
Elmar Herbst, MD, PhD, Muenster GERMANY
Christoph Kittl, MD, MD(res), Muenster GERMANY
Department of Trauma, Hand and Reconstructive Surgery, University Hospital Münster, Münster, NRW, GERMANY
FDA Status Not Applicable
Summary
The presented knee joint simulator exhibits excellent repeatability, responsiveness, and strong correlation with the gold standard robotic test setup, making it suitable for use in biomechanical studies of the knee joint.
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Abstract
Background
Various simulators and experimental setups are available for the assessment and evaluation of native and pathological kinematics of the human knee joint, each with different advantages and disadvantages.
Purpose
The aim of this study was to validate a novel experimental test setup for assessing human knee joint kinematics.
Methods
A novel knee joint simulator was designed. In the simulator the femur is rigidly mounted to the simulator, while the tibia is allowed to float freely, allowing movements of the knee joint in all six degrees of freedom. Movements are applied to the knee joint by a cable pulley system, to which static weights are applied. A continuous axial compression of the joint is achieved through axial loading of the tibia via a spherical roller bearing. The movements of the knee joint in the spatial planes were recorded using a commercial stereo-optical measurement system (ARAMIS, GOM GmbH). For validation, four human cadaveric knee joints were used. The following test protocol was conducted to analyze knee joint movements: Under 200 N axial compression at 0°, 30°, 60°, and 90° knee flexion: 89N anterior/posterior tibial translation (ATT/PTT), 5 Nm internal rotation (IR)/external rotation (ER), and 8 Nm varus (VR)/valgus (VL). Each movement was repeated five times in the native state to determine the repeatability (via intraclass correlation coefficient (ICC)). Subsequently, the anterior cruciate ligament (ACL) and the lateral collateral ligament (LCL) were sequentially severed to assess the system’s responsiveness (whether changes in the knee joint condition could be significantly detected). For external validation, the native knee kinematics were assessed in a six degrees of freedom robotic test setup (gold standard). The kinematics of the novel knee joint simulator and the gold standard were compared, using Pearson’s correlation coefficient. Statistical analysis was performed using PRISM (GraphPad Software) and Excel (Microsoft).
Results
Excellent repeatability of the individual movements was demonstrated, with an ICC of ≥ 0.98 for each of the six movements (indicating excellent repeatability). After severing the ACL, a significant increase in ATT was observed in all degrees of flexion (p < 0.05). After severing the LCL, a significant increase under varus load was observed in all degrees of flexion (p < 0.05), indicating responsiveness of the knee simulator to changes in the state of the knee joint. Finally, the measurements of the knee joint simulator showed significant correlations with the gold standard in all assessed movements, with correlation coefficients between 0.54 and 0,86.
Conclusion
The presented knee joint simulator exhibits excellent repeatability, responsiveness, and strong correlation with the gold standard robotic test setup, making it suitable for use in biomechanical studies of the knee joint.