Design, Evaluation, and Implementation of a Novel Magnetic Resonance Imaging-Compatible Physiologic Loading Simulator...

Area of Science:

• Biomechanics
• Biomedical Engineering
• Medical Imaging

Background:

• Quantitative magnetic resonance imaging (qMRI) combined with mechanical testing can reveal relationships between loading and joint/tissue function.
• Existing MRI-compatible testing devices are limited to uniaxial compression, low loads, or single-tissue analysis, hindering comprehensive joint investigation.
• Complex biomechanical simulators often lack MRI compatibility, limiting in-situ functional assessment.

Purpose of the Study:

• To design, construct, and validate an MRI-compatible multi-axial load-control system for cadaveric joints.
• To enable simulation of physiologically relevant, multi-axial loading conditions, including gait, within an MRI environment.
• To investigate joint and tissue function under realistic loading scenarios using qMRI.

Main Methods:

• Development of a portable, MRI-compatible loading device utilizing pneumatic actuators for multi-axial control.
• Integration of axial compression (≤2.5 kN), shear (≤1 kN), bending (≤30 N·m), and muscle tension simulation.
• Experimental testing on a cadaver knee specimen, including validation of physiological loading conditions and repeatability assessment using force/pressure sensors.

Main Results:

• The system successfully simulated healthy and pathologic gait loading (stance/swing) with good repeatability (e.g., 1.23-2.91% CV for axial compression).
• Repeatability was comparable to state-of-the-art simulators, yielding consistent joint contact responses.
• Contact measurements showed expected tibiofemoral and patellofemoral load transfer and localized high contact pressures consistent with literature.

Conclusions:

• The developed MRI-compatible multi-axial loading system effectively simulates physiologically relevant gait loading in cadaver knees.
• This technology advances the capability to study joint mechanics and tissue response under complex loading conditions using qMRI.
• The system provides a valuable tool for research into joint health, disease, and the effects of physical loading.