Comparison of OpenSim and AnyBody modeling system™ predictions in biomechanical modeling of upper extremities

Abstract

Background: The study of muscle forces in upper extremities is pivotal for advancements in biomechanical modeling, contributing significantly to the field of orthopedics, rehabilitation, and sports science. Despite the prominence of OpenSim and AnyBody modeling system™ in this domain, a gap persists in comparative analyses specifically targeting muscle force predictions in upper extremity motions. Methods: This study compares the predictions of muscle forces in static elbow flexion, shoulder flexion, and shoulder abduction using OpenSim and AnyBody modeling systemTM, hypothesizing significant differences in predictions attributable to their distinct modeling methodologies and assumptions. This work utilized generic models without subject-specific data and conducted simulations in both software environments, focusing on the magnitude and activation of major muscle forces under predefined kinematics. Results: OpenSim and AnyBody modeling systemTM produced similar results when simulating elbow flexion, with both software predicting forces in the major muscles required to maintain the posture. However, discrepancies were observed between the two software for muscle force predictions during the shoulder flexion and abduction movements. AnyBody modeling systemTM appeared to be more robust as it included all the upper extremity muscles and predicted the major muscles forces required for these movements more accurately compared to OpenSim. Conclusions: The results of this study show significant differences in muscle force predictions between OpenSim and AnyBody modeling systemTM, attributed to the unique modeling approaches, especially in representing muscle-tendon complexes and joint dynamics.