Synopsis

The overall goal of this case study is to provide the utility of Open Knee(s) - Generation 1 model for reproducing the outcome of a clinical test, the pivot shift, for evaluating mechanical function of the anterior cruciate ligament.

Use Case

The case is based on reproduction of a pivot shift loading scenario in a tibiofemoral joint model. The loading scenario was measured in a cadaver knee during pivot shift tests conducted by an orthopaedic surgeon. In follow-up robotics testing, this loading profile was adjusted for robotics testing of intact, ACL deficient, and ACL reconstructed knees. The use case aims for illustrating the capacity of the Open Knee(s) - Generation 1 model to reproduce the clinical differentiation of intact and ACL deficient knee in a virtual sense.

Simulation Aims

• To understand the role of ACL for stabilization of the joint during pivot shift testing (primary)
• To explore the correspondence of Open Knee(s) simulation against robotics prescribed pivot shift loading of various knees (secondary)

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

Prescribed time histories of movement and loading of the tibiofemoral joint (six degrees of freedom) representative of pivot shift data:

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

Outputs

• Time histories of kinematics-kinetics of the tibiofemoral joint (six degrees of freedom) (primary)
  • flexion torque
  • internal/external rotation
  • varus/valgus
  • anterior/posterior translation
  • medial/lateral translation
  • compression/distraction
• Time histories of stress-strain behavior (secondary)

Simulation Conditions

• with intact ACL
• without the ACL (very low stiffness for convenient modeling and simulation workflow)

Team Members

• Ahmet Erdemir - study planning, outline of publications
• Snehal Chokhandre - execution of simulations and post-processing, lead authorship in publications
• Craig Bennetts - assisting simulations, scripting for pre-/post-processing, support to document model in publications
• Tara Bonner - assiting pivot shift trajectory generation, support documentation on pivot shift literature and implications of simulations for robotics testing
• Robb Colbrunn - lead pivot shift trajectory generation, provide literature survey on pivot shift studies (clinical and cadaver testing), support to document implications of simulations for robotics testing
• Paul Saluan - support to document clinical utility of pivot shift and implications of simulations for clinical practice

Progress

Source Code Repository

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

Data

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

Model Customization

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

Simulations

Post-Processing

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

Publications

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

References