Abstract
BackgroundMusculoskeletal modelling is used to assess musculoskeletal loading during gait. Linear scaling methods are used to personalize generic models to each participant's anthropometry. This approach introduces simplifications, especially when used in paediatric and/or pathological populations. This study aimed to compare results from musculoskeletal simulations using various models ranging from linear scaled to highly subject-specific models, i.e., including the participant's musculoskeletal geometry and electromyography data. MethodsMagnetic resonance images (MRI) and gait data of one typically developing child and three children with cerebral palsy were analysed. Musculoskeletal simulations were performed to calculate joint kinematics, joint kinetics, muscle forces and joint contact forces using four modelling frameworks: 1) Generic-scaled model with static optimization, 2) Generic-scaled model with an electromyography-informed approach, 3) MRI-based model with static optimization, and 4) MRI-based model with an electromyography-informed approach. FindingsRoot-mean-square-differences in joint kinematics and kinetics between generic-scaled and MRI-based models were below 5° and 0.15 Nm/kg, respectively. Root-mean-square-differences over all muscles was below 0.2 body weight for every participant. Root-mean-square-differences in joint contact forces between the different modelling frameworks were up to 2.2 body weight. Comparing the simulation results from the typically developing child with the results from the children with cerebral palsy showed similar root-mean-square-differences for all modelling frameworks. InterpretationIn our participants, the impact of MRI-based models on joint contact forces was higher than the impact of including electromyography. Clinical reasoning based on overall root-mean-square-differences in musculoskeletal simulation results between healthy and pathological participants are unlikely to be affected by the modelling choice.
Highlights
Musculoskeletal simulations have been used to answer research questions on musculoskeletal loading in paediatric and pathological populations (Kainz et al, 2020; Steele et al, 2012b; Wesseling et al, 2016)
RMSD in joint kinematics and kinetics between the generic-scaled and magnetic resonance images (MRI) models were below 5◦ and 0.12 Nm/kg, respectively (Fig. 4)
Hip and knee joint contact force (JCF) were sensitive to the inclusion of subject-specific geometry, whereas ankle JCF were more sensitive to the inclusion of EMG data in most cerebral palsy (CP) participants
Summary
Musculoskeletal simulations have been used to answer research questions on musculoskeletal loading in paediatric and pathological populations (Kainz et al, 2020; Steele et al, 2012b; Wesseling et al, 2016). A generic musculoskeletal model developed from cadaveric data of an adult is scaled to the anthropometry of the child (Delp et al, 2007). This procedure neglects subject-specific musculo skeletal geometry, e.g., subject and age-specific femoral neck-shaft angle (Bobroff et al, 1999). In children with cerebral palsy (CP), only a small number of studies have compared generic scaled with medical imaging-based models. Comparing the simulation results from the typically developing child with the results from the children with cerebral palsy showed similar root-mean-squaredifferences for all modelling frameworks. Clinical reasoning based on overall root-mean-square-differences in musculoskeletal simulation results between healthy and pathological participants are unlikely to be affected by the modelling choice
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