A Shoulder Musculoskeletal Model with Three-Dimensional Complex Muscle Geometries

Area of Science:

• Biomechanics
• Computational Modeling
• Anatomy

Background:

• Traditional musculoskeletal models use simplified line segments for muscle geometry, limiting accuracy in predicting complex muscle paths and interactions.
• Existing models struggle to represent how muscle shape changes and interacts with moving bones and joints.
• The assumption of equivalent moment arms for all muscle fibers in simplified models is a significant limitation.

Purpose of the Study:

• To develop a shoulder musculoskeletal model incorporating complex, realistic muscle geometries.
• To enhance the anatomical fidelity of computational musculoskeletal models.
• To improve the simulation of shoulder movements and muscle fiber lines of action.

Main Methods:

• An automated technique was used to reconstruct the detailed fiber shape within the entire volume of six shoulder muscles.
• Fibers were generated from the skeletal muscle's surface geometry and attachment areas, creating highly discretized muscle representations.
• Simulations of various shoulder movements were performed using these detailed models, and moment arms were calculated.

Main Results:

• The developed musculoskeletal models produced more realistic muscle geometries compared to traditional line-segment methods.
• The new models offer an expanded physical representation of muscles, capturing complex shapes and interactions.
• Calculated moment arms were validated against cadaveric measurements and existing literature models.

Conclusions:

• The created shoulder musculoskeletal model with complex muscle geometry significantly increases anatomical realism.
• This advanced modeling approach enhances the accurate representation of muscle fiber lines of action.
• The model provides a foundation for advanced finite element analyses of shoulder biomechanics.