The geometrical representation of muscles in computational models of the musculoskeletal system typically consists of a series of line segments. These muscle anatomies are based on measurements from a limited number of cadaveric studies that recently have been used as atlases for creating subject-specific models from medical images, so potentially restricting the options for personalisation and assessment of muscle geometrical models. To overcome this methodological limitation, we propose a novel, completely automated technique that, from a surface geometry of a skeletal muscle and its attachment areas, can generate an arbitrary number of lines of action (fibres) composed by a user-defined number of straight-line segments. These fibres can be included in standard musculoskeletal models and used in biomechanical simulations. This methodology was applied to the surfaces of four muscles surrounding the hip joint (iliacus, psoas, gluteus maximus and gluteus medius), segmented on magnetic resonance imaging scans from a cadaveric dataset, for which highly discretised muscle representations were created and used to simulate functional tasks. The fibres’ moment arms were validated against measurements and models of the same muscles from the literature with promising outcomes. The proposed approach is expected to improve the anatomical representation of skeletal muscles in personalised biomechanical models and finite element applications.
This project aims to contribute to musculoskeletal modelling by presenting a fully automated method for generating anatomical muscle models from segmented geometries typically obtained from MRI scans. For each muscle geometry, the method creates an arbitrary number of lines of action of user-defined complexity, i.e. number of segments in the muscle path.
The package available for download consists of musculoskeletal models of the hip joint, including "traditional" and highly-discretised muscle representations, and all the MATLAB scripts and data required to generate the main results and figures presented in the associated publication.
Please note that all the materials and scripts for this publication were developed using the API of OpenSim 3.3. More information about requirements, limitation and intended use of the resources and data shared with the publication are available in the "README.pdf" file within the package and at our GitHub project page: https://github.com/ComputationalBiomechanics/3d-muscles.
The highly-discretised muscle models included in the package were generated automatically using the method described in the paper through a software called LHPBuilder, a multimodal viewer for biomechanical applications that is not developed or supported anymore. The same method is currently being implemented as an OpenSim (v4.1) plugin, a demo of which is visible here:
Release of the plugin will be associated with a future publication.