The effects of anatomical errors on shoulder kinematics computed using multi-body models

Area of Science:

• Biomechanics
• Medical Imaging
• Human Movement Analysis

Background:

• Multi-body models and inverse kinematics offer advantages for calculating joint motion over marker-based methods.
• Computed joint kinematics can be sensitive to the chosen model, participant anthropometry, and sex.

Purpose of the Study:

• To compare shoulder kinematics derived from an anatomical, MRI-based model against a scaled-generic model.
• To quantify the impact of anatomical errors and participant characteristics on calculated joint angles.

Main Methods:

• Developed participant-specific multi-body shoulder models using both image-based and scaled-generic approaches.
• Captured planar shoulder movements experimentally and performed inverse kinematics using both modeling procedures.
• Analyzed results using Bland-Altman analysis and multi-linear regressions.

Main Results:

• Anatomical and scaled-generic models yielded average kinematic differences of 3.2–5.4 degrees, task-dependent.
• The MRI-based anatomical model showed better agreement with direct kinematics than the scaled-generic model.
• Anatomical errors, sex, and BMI explained 41–80% of kinematic variability between models.

Conclusions:

• Modeling precision significantly impacts shoulder kinematics calculations.
• Anatomical errors and individual anthropometric factors influence computed joint angles.
• Accurate, individualized models are crucial for reliable shoulder kinematics analysis.