In this project, previously collected motion capture data was analyzed and used to calculate musculoskeletal loadings. Following three participant groups were analyzed:
• 10 typically developing children
• 14 children with cerebral palsy before and after receiving Botulin Toxin-A injections
• 25 children with cerebral palsy before and after receiving a selective dorsal rhizotomy
Many children with cerebral palsy have an abnormal motor control. Considering that the standard musculoskeletal modelling workflow uses an approach to calculate muscle forces, which does not differentiate between normal and pathological motor control, we also investigated the impact of including electromyography data to account for the subject-specific motor control on the musculoskeletal simulation results.
Most generic musculoskeletal model are based on a bony geometry of an adult person. Hence, we also investigated how a modified child-specific femoral geometry in a musculoskeletal model influence hip joint contact forces, which have the biggest impact on femoral bone growth simulations.
During the development of the multi-scale bone growth prediction workflow we had to address several technical question. First, we developed a workflow to create a subject-specific finite element model of the femur of a child based on magnetic resonance images. This workflow, however, was too slow to create a patient-specific model for each participant. Hence, we developed a workflow in which we could morph the finite element model to different femoral geometries (Fig. 1). Using this workflow, we showed how the femoral geometry influence growth predictions. Furthermore, in a study based on simplified loading conditions, we compared two growth direction methods and showed that only the ‘average neck deflection’ method leads to reasonable results.
In the final study we showed that Botulinum-Toxin A injections have a minor impact on femoral bone growth. Furthermore, we showed that selective dorsal rhizotomy has a positive impact on femoral bone growth. Additionally, we investigated difference between children with cerebral palsy who have typically developing bone growth and who have pathological femoral growth. Our findings showed that the main difference is caused by a different pelvic and hip movement strategy during mid-stance of the gait cycle, which leads to a less posterior oriented hip joint contact force in children with pathological femoral growth.
Dissemination of results
The project led to five peer-reviewed full papers in top international journals (2 published, 2 under review, 1 in preparation), four published conference abstracts and six conference presentations. Furthermore, I was selected as a finalist for the ‘Clinical Biomechanist Award’ from the European Society of Biomechanics. Hence, in July 2020 I will present the findings of this project in a webinar (due to COVID-19) together with three more finalist.
