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In-vitro validation of inertial-sensor-to-bone alignment.
Ive Weygers1, Manon Kok2, Thomas Seel3
1KU Leuven campus Bruges, Department of Rehabilitation Sciences, 8200 Bruges, Belgium.
Journal of Biomechanics
|October 10, 2021
Summary
Accurate alignment of inertial sensors to bone is crucial for reliable kinematic estimation. This study introduces a novel anatomical ground truth for validating model-based alignment methods, revealing limitations in secondary kinematic axis identification.
Area of Science:
- Biomechanics
- Biomedical Engineering
- Orthopedics
Background:
- Accurate kinematic estimation using skin-attached inertial sensors requires precise alignment between sensor and bone coordinate systems.
- Model-based alignment methods offer an alternative to calibration movements but their accuracy in aligning sensor and segment axes is not well-established.
- Validating alignment models is challenging due to inherent limitations in traditional optical motion capture ground truths.
Purpose of the Study:
- To present a novel anatomical tibiofemoral ground truth for validating model-based inertial sensor-to-bone alignment.
- To assess the accuracy of existing model-based alignment strategies in aligning sensor axes with underlying segment axes.
- To investigate the influence of joint biomechanics on the accuracy of secondary kinematic axis identification.
Main Methods:
- Development of an anatomical tibiofemoral ground truth using an unloaded cadaveric setup to minimize soft tissue and palpation errors.
- Validation of existing model-based inertial sensor-to-bone alignment strategies against the established ground truth.
- Analysis of how modeling joint degrees of freedom and utilizing rich movement data influences the identification of underlying joint axes.
Main Results:
- The primary sagittal rotation axis alignment demonstrated good correlation with the segment-embedded reference.
- Axes related to secondary kinematics showed deviations from segment-embedded axes, proportional to their expected range of motion.
- Relative inertial sensor orientation and diverse movements aided in identifying underlying joint axes.
Conclusions:
- The developed anatomical ground truth provides a robust method for validating inertial sensor-to-bone alignment.
- Current model-based alignment strategies show limitations in accurately capturing secondary joint kinematics.
- Future alignment models need to incorporate detailed joint biomechanics for improved interpretation of secondary kinematics.
