Description
Thesis at UoA. I created scaled and subject-specific models of the lower limb of a typically developed child and a child with cerebral palsy to compare the estimated structure and function of the models using Python and OpenSim. I found that the differences in structure lead to differences in the estimated joint kinematics and muscle forces, highlighting the importance of using accurate geometries in musculoskeletal models. The methods established can also be used to investigate relationships between the accuracy of modelling methods and the severity of a child's cerebral palsy.
Inspiration
Research involving children can be more challenging than research involving adults, leading to a shortage of paediatric research and resulting in children being treated as small adults. This assumption is not always valid for typically developed children and children with cerebral palsy with impaired posture and movement. The musculoskeletal system plays a key role in movement. Musculoskeletal models can be used to simulate movement and study the structure and function of the musculoskeletal system. To estimate the function accurately, the structure must be accurately modelled. Existing methods include scaling generic adult models, segmenting medical images to create subject-specific models, and making predictions from statistical shape models. Currently, there is limited research comparing scaled and subject-specific models for children.
Process
This project aimed to create scaled and subject-specific models of the lower limbs of a typically developed (TD) child and a child with cerebral palsy (CP) and to compare the estimated structure and function between the scaled and subject-specific models.
Lower limb bones and muscles were segmented from medical images of a TD child and a child with CP. A workflow was established to create a subject-specific OpenSim model of the TD child. A scaled OpenSim from a generic adult model was also built to compare joint kinematics, kinetics, and muscle forces. The bone meshes generated for the TD child and child with CP by 1) the scaled model, 2) the statistical shape model, and 3) the subject-specific model were compared.
Learnings
The meshes of TD child were more accurate than those of the child with CP for each modelling method. The shape model predicted bone meshes were more accurate to the subject-specific reconstructed surfaces than the scaled meshes for both children, suggesting that the paediatric shape model could provide a good alternative to subject-specific modelling. Differences in the scaled and subject-specific models' structure lead to differences in the estimated joint kinematics and muscle forces, highlighting the importance of having accurate geometries in musculoskeletal models. The methods established in this project can be used to investigate relationships between the accuracy of various modelling methods and the severity of a child's cerebral palsy. This would give a more complete understanding of the effects of differences in structure on the function of the musculoskeletal system and recommendations for which modelling method to use in different applications.