Benchmarking of dynamic simulation predictions in two software platforms using an upper limb musculoskeletal model

Abstract

Several opensource or commercially available software platforms are widely used to develop dynamic simulations of movement. While computational approaches are conceptually similar across platforms, technical differences in implementation may influence output. We present a new upper limb dynamic model as a tool to evaluate potential differences in predictive behavior between platforms. We evaluated to what extent differences in technical implementations in popular simulation software environments result in differences in kinematic predictions for single and multijoint movements using EMG- and optimization-based approaches for deriving control signals. We illustrate the benchmarking comparison using SIMM-Dynamics Pipeline-SD/Fast and OpenSim platforms. The most substantial divergence results from differences in muscle model and actuator paths. This model is a valuable resource and is available for download by other researchers. The model, data, and simulation results presented here can be used by future researchers to benchmark other software platforms and software upgrades for these two platforms.

Keywords: biomechanics; computational modeling; medical computing; musculoskeletal; neuromuscular.

Figure 1

Musculoskeletal model of the upper limb. Musculoskeletal model of the upper limb. The dynamic model incorporates 7 degrees of freedom, including A) shoulder rotation and elevation (thoracohumeral angle) and wrist flexion, B) wrist deviation and elbow flexion, and C) elevation plane of the shoulder and forearm rotation. 50 musculotendon actuators spanning these joints are also included.

Figure 2

Joint kinematics for a single trial of EMG-driven forward dynamic simulation at the A) wrist, B) elbow, and C) shoulder. Trials were selected as the trial with minimum RMSE between the simulation and experimental kinematics. OpenSim (black) simulations match well with simulations in the SIMM-SD/Fast (dark grey) platform.

Figure 3

Forward dynamic simulation kinematics driven using CMC-derived controls in OpenSim (dark grey) and SIMM-SD/Fast (light grey) compared to CMC-derived joint kinematics as calculated in OpenSim (black). The movement began at 0.63 sec in this trial as defined in the text, and was simulated from this point. The CMC-driven forward dynamic simulation in OpenSim tracks the CMC kinematics closely (thus the curves overlay in this figure), while the same controls in SIMM-SD/Fast result in a movement that is substantially altered from the desired kinematics, due to the different mechanical properties of the underlying model implementation.

Figure 4

Gravity-driven forward dynamic simulation without muscles (left column), with passive muscles (center column), and with a subset of muscles implemented identically between platforms (right column) at the A-C) wrist, D-F) elbow, and G-I) shoulder. OpenSim (black) simulations and SIMM-SD/Fast (dark grey) simulations perform nearly identically when muscles are absent and only kinematics, inertial properties, damping, and joint restraint torques are present. At the elbow and wrist, average postures toward the end of the simulations differ between the simulations in the presence of all muscles. At the elbow and shoulder, when muscle actuators are eliminated that were not able to be implemented identically, differences between platforms are reduced.