Musculoskeletal full-body models including a detailed thoracolumbar spine for children and adolescents aged 6-18 years

TL;DR

This paper introduces detailed full-body musculoskeletal models for children and adolescents aged 6-18, validated against in vivo data, enabling accurate simulations of trunk muscle strength, spinal loading, and activity for this age group.

Contribution

The authors developed and validated age-specific full-body musculoskeletal models including a detailed thoracolumbar spine for children and adolescents, filling a gap in existing adult-based models.

Findings

High correlation between model predictions and in vivo data for muscle strength and spinal loading.

Models accurately predict trunk muscle activity and segmental loading in children and adolescents.

Framework can be adapted for pathological conditions like scoliosis.

Abstract

Currently available musculoskeletal inverse-dynamics thoracolumbar spine models are entirely based on data from adults and might therefore not be applicable for simulations in children and adolescents. In addition, these models lack lower extremities, which are required for comprehensive evaluations of functional activities or therapeutic exercises. We therefore created OpenSim-based musculoskeletal full-body models including a detailed thoracolumbar spine for children and adolescents aged 6-18 years and validated by comparing model predictions to in vivo data. After combining our recently developed adult thoracolumbar spine model with a lower extremity model, children and adolescent models were created for each year of age by adjusting segmental length and mass distribution, center of mass positions and moments of inertia of the major body segments as well as sagittal pelvis and spine alignment based on literature data. Similarly, muscle strength properties were adjusted based on CT-derived cross-sectional area measurements. Simulations were conducted from in vivo studies reported in the literature involving children and adolescents evaluating maximum trunk muscle strength (MTMS), lumbar disc compressibility (LDC), intradiscal pressure (IDP) and trunk muscle activity (MA). Model predictions correlated highly with in vivo data (MTMS: r>=0.82, p<=0.03; LDC: r=0.77, p<0.001; IDP: r>=0.78, p<0.001; MA: r>=0.90, p<0.001), indicating suitability for the reasonably accurate prediction of maximal trunk muscle strength, segmental loading and trunk muscle activity in children and adolescents. When aiming at investigating children or adolescents with pathologies such as idiopathic scoliosis, our models can serve as a basis for the creation of deformed spine models and for comparative purposes.