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bioRxiv · 10.1101/319616

Simulating Contact Using the Elastic Foundation Algorithm in OpenSim

Hast, M. W.·Hanson, B. G.·Baxter, J. R.
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Abstract

Modeling joint contact is necessary to test many questions using simulation paradigms, but this portion of OpenSim is not well understood. The purpose of this study was to provide a guide for implementing a validated elastic foundation contact model in OpenSim. First, the load-displacement properties of a stainless steel ball bearing and ultra high molecular weight polyethylene (UHMWPE) slab were recorded during a controlled physical experiment. These geometries were imported and into OpenSim and contact mechanics were modeled with the on-board elastic foundation algorithm. Particle swarm optimization was performed to determine the elastic foundation model stiffness (2.14x1011 {+/-} 6.81x109 N/m) and dissipation constants (0.999 {+/-} 0.003). Estimations of contact forces compared favorably with blinded experimental data (root mean square error: 87.58 {+/-} 1.57 N). Last, total knee replacement geometry was used to perform a sensitivity analysis of material stiffness and mesh density with regard to penetration depth and computational time. These simulations demonstrated that material stiffnesses between 1011 and 1012 N/m resulted in realistic penetrations (< 0.15mm) when subjected to 981N loads. Material stiffnesses between 1013 and 1015 N/m increased computation time by factors of 12-23. This study shows the utility of performing a simple physical experiment to tune model parameters when physical components of orthopaedic implants are not available to the researcher. It also demonstrates the efficacy of employing the on-board elastic foundation algorithm to create realistic simulations of contact between orthopaedic implants.

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Hast, M. W., Hanson, B. G., Baxter, J. R.. 2018-05-10. Simulating Contact Using the Elastic Foundation Algorithm in OpenSim. https://doi.org/10.1101/319616

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