Sensitivity of model-predicted muscle forces of patients with cerebral palsy to variations in muscle-tendon parameters

Abstract

Computational musculoskeletal modeling and simulation platforms are efficient tools to gain insight into the muscular coordination of patients with motor disabilities such as cerebral palsy (CP). Muscle force predictions from simulation programs are influenced by the architectural and contractile properties of muscle-tendon units. In this study, we aimed to evaluate the sensitivity of major lower limb muscle forces in patients with CP to changes in muscle-tendon parameters. Open-access datasets of children with CP (n=8) and healthy children (n=8) were considered. Monte Carlo analysis was executed to specify how sensitive the muscle forces to perturbations between +10% and −10% of the nominal value of the maximum isometric muscle force, optimal muscle fiber length, muscle pennation angle, tendon slack length, and maximum contraction velocity of muscle. The sensitivity analysis revealed that muscle forces of CP patients and healthy individuals were most sensitive to perturbations in the tendon slack length (p<0.05), while forces of CP patients were more sensitive to tendon slack length when compared to the healthy group (p<0.05). Muscle forces of patients and healthy individuals were insensitive to the other four parameters (p>0.05), except for the gracilis and sartorius muscles in which the proportion of optimal muscle fiber length to tendon slack length is higher than 1; forces of these two muscles were also sensitive to the optimal muscle fiber length. The results of this study are expected to contribute to our understanding of which parameters should be personalized when conducting musculoskeletal modeling and simulation of patients with CP.