How Different Marker Sets Affect Joint Angles in Inverse Kinematics Framework.

Area of Science:

• Biomechanics
• Motion Analysis
• Human Movement Science

Background:

• Marker set selection introduces variability in motion analysis.
• Existing research on marker set performance primarily uses direct kinematics, limiting applicability to inverse kinematics.

Purpose of the Study:

• To investigate the sensitivity of kinematic outcomes to inter-marker set variability within an inverse kinematic framework.
• To compare the performance of Plug-in-Gait, University of Ottawa, and a three-marker-cluster marker set.

Main Methods:

• Walking trials of 12 participants were analyzed using OpenSim software.
• Three distinct marker sets were applied to the same participants and model.
• Coefficient of multiple correlations and absolute reliability indices (minimum detectable change) were calculated.

Main Results:

• Coefficient of multiple correlations indicated good to very good reliability for sagittal and coronal plane angles, but lower for the transverse plane.
• Minimum detectable change values varied from 3° (hip sagittal) to 16.6° (hip transverse).
• Significant differences (P < 0.001) in hip and knee abduction/adduction and hip/ankle rotations were observed among marker sets, with Plug-in-Gait yielding larger ranges of motion.

Conclusions:

• Marker set choice critically influences inverse kinematic results, even with the same biomechanical model.
• High minimum detectable changes suggest caution when comparing studies using different marker configurations, particularly concerning joint-defining markers.