A soft tissue artefact model driven by proximal and distal joint kinematics

Area of Science:

• Biomechanics
• Human Movement Analysis
• Medical Imaging

Background:

• Stereophotogrammetry relies on skin-markers to analyze human movement.
• Soft tissue artefact (STA) describes marker movement relative to underlying bone.
• Accurate STA estimation is crucial for skeletal kinematics and simulation.

Purpose of the Study:

• To devise and assess a mathematical model for estimating subject- and marker-specific STAs.
• To investigate the primary causes of thigh STAs during human movement.
• To evaluate the model's feasibility for in vivo and ex vivo applications and its generalizability.

Main Methods:

• Developed a mathematical model based on hypotheses of skin sliding and linear relationships.
• Tested the model using passive hip/knee movements in non-obese subjects and running volunteers.
• Utilized both skin- and pin-markers for data acquisition and validation.

Main Results:

• The proposed model demonstrated successful calibration with minimal residuals.
• Results confirmed that thigh artefacts are predominantly caused by skin sliding, both ex vivo and in vivo.
• Unreconstructed artefacts in vivo were linked to soft tissue wobbling with low power contribution.

Conclusions:

• The developed mathematical model is feasible for estimating STAs in both ex vivo and in vivo scenarios.
• The model architecture can be integrated into skeletal kinematics estimators.
• Calibrated models show generalizability across similar movement patterns, enabling realistic STA generation for simulations.