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

• To understand the role of joint loading on convergence characteristics
• To understand the role of simulation (numerical analysis) parameters on convergence characteristics
• To understand model parameters on convergence characteristics
• To understand new model features on convergence characteristics

Model

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

• https://simtk.org/svn/openknee/_gen1/src/tf_joint_FEBio_v2.feb

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):

• flexion internal/external rotation torque varus/valgus torque anterior/posterior force medial/lateral force compression/distraction force

Outputs

• Convergence metrics (primary)
  • Completion of simulation (Yes/No)
  • If not completed - time point at which the simulation crashed
  • If completed - computation time (also provide computer specifications), number of iterations
• Time histories of kinematics-kinetics of the tibiofemoral joint (six degrees of freedom) (secondary)
  • flexion torque
  • internal/external rotation
  • varus/valgus
  • anterior/posterior translation
  • medial/lateral translation
  • compression/distraction
• Post-processed joint mechanics information (secondary)
  • Comparison of tibia kinetics and femur kinetics
  • Comparison of tibiofemoral joint kinematics to baseline simulation results
• Time histories of stress-strain behavior (secondary)

Simulation Conditions

• Simulation (numerical analysis) parameters
• Model parameters
  • Increase of menisci circumferential modulus
  • Increase of cartilage modulus (relative to menisci)
  • Increase of ligament fiber moduli
• Model changes
  • Addition of transverse ligament
  • Distributed attachment of meniscal horns
  • Attachment of medial meniscus to medial collateral ligament
  • Attachment of lateral and medial menisci to tibia
  • Application of in situ ligament strain
  • Additional ligaments
• Loading conditions
  • passive flexion
  • internal/external rotation laxity
  • anterior-posterior translation laxity
  • varus/valgus laxity
  • pivot shift

Team Members

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