Dynamic Musculoskeletal Simulation of a Passive Exoskeleton for Simulating Contracture

Area of Science:

• Biomechanics
• Musculoskeletal modeling
• Gait analysis

Background:

• Gait assessment scores are crucial for quantifying gait abnormalities but their clinical acceptance is hindered by unreliable performance evaluation methods.
• Current assessment methods for gait scores are prone to errors due to variations in patient populations and observers, affecting reliability and sensitivity.
• There is a need for a reproducible methodology to simulate musculoskeletal deformations, like contractures, for objective gait assessment score evaluation.

Purpose of the Study:

• To develop and verify a mathematical model of a passive exoskeleton capable of simulating musculoskeletal deformations, specifically contractures.
• To create a reliable method for objectively evaluating the performance of gait assessment scores across varying severities of simulated contractures.
• To assess the accuracy and robustness of the proposed simulation model under different conditions and perturbations.

Main Methods:

• Dynamic musculoskeletal simulations were employed to model and verify a passive exoskeleton system.
• The model was tested using five unique combinations of linear and non-linear torques.
• Simulations included seven degrees of severity for hamstring contracture and were subjected to various environmental perturbations.

Main Results:

• The proposed model demonstrated high accuracy, achieving a root mean square error of 1.864° and a correlation coefficient of 0.984.
• The model successfully simulated hamstring contractures with varying degrees of severity and different torque inputs.
• Performance testing under environmental perturbations indicated the model's tolerance to noise, confirming its robustness.

Conclusions:

• A passive exoskeleton attached to an unimpaired musculoskeletal model can accurately simulate targeted muscle contractures.
• The developed methodology provides a valuable tool for objectively evaluating gait assessment score performance.
• This approach aids in understanding the biomechanical effects of contractures on gait, enhancing clinical relevance and diagnostic capabilities.