TableOfContents

Synopsis

The overall goal of this case study is to understand convergence characteristics of Open Knee(s) - Generation 1 model to conduct simulations in an efficient and effective manner.

Use Case

The case relies on simulations of varying levels of tibiofemoral joint loading to evaluate the performance of the model in terms of convergence while reasonably predicting joint mechanics. Convergence is defined by the ease and speed of simulations. Relative predictive accuracy evaluates changes in predicted joint kinematics and tissue stress-strain distributions.

Simulation Aims

Model

The model is based on Open Knee(s) - Generation 1 model, which was updated for FEBio version 2.1:

Inputs

The loading and boundary conditions relies on prescribed time histories of movement and loading of the tibiofemoral joint (six degrees of freedom) for various loading scenarios (see Simulation Conditions):

Outputs

Simulation Conditions


Use Cases


max_retries & max_refs

Parameter permutations:

Converged:

Ranking:

  1. max_retries = 5, max_refs = 20
  2. max_retries = 20, max_refs = 20

both have similar results

Results: https://simtk.org/svn/openknee/app/Convergence/sol/max_retries_refs_1/


flexion angle & Anterior-Posterior (AP) force

SET 1

Parameter permutations:

Converged:

Non-converged:

Results: https://simtk.org/svn/openknee/app/Convergence/sol/flexion_AP_1/

SET 2

Parameter permutations:

Converged:

Non-converged:

Results: https://simtk.org/svn/openknee/app/Convergence/sol/flexion_AP_2/


flexion angle & Internal-External (IE) torque

SET 1

Parameter permutations:

Converged:

Nonconverged

Results: https://simtk.org/svn/openknee/app/Convergence/sol/flexion_IE_1/

SET 2

Parameter permutations:

Nonconverged:

Results: https://simtk.org/svn/openknee/app/Convergence/sol/flexion_IE_2/


flexion angle & Varus-Valgus (VV) torque

SET 1

Parameter permutations:

Converged:

Nonconverged:

Results: https://simtk.org/svn/openknee/app/Convergence/sol/flexion_VV_1/

SET 2

Parameter permutations:

Converged:

Nonconverged:

Results: https://simtk.org/svn/openknee/app/Convergence/sol/flexion_VV_2/


Team Members

Ahmet Erdemir - study planning, assisting simulations, interpretation of results

Craig Bennetts - scripting for large scale analysis, execution of simulations, interpretation of results

Snehal Chokhandre - execution of simulations, interpretation of results

Progress

Source Code Repository

https://simtk.org/svn/openknee/app/Convergence/

Data

https://simtk.org/svn/openknee/app/Convergence/dat/

Model Customization

https://simtk.org/svn/openknee/app/Convergence/src/

Simulations

Post-Processing

https://simtk.org/svn/openknee/app/Convergence/sol/

Publications

https://simtk.org/svn/openknee/app/Convergence/doc/

References