1. Open Knee: Capacity to Reproduce Anterior Cruciate Ligament Deformations Ahmet Erdemir and Scott Sibole Computational Biomodeling Core Department of Biomedical Engineering Cleveland Clinic April 13, 2012 CMBBE 2012, Berlin, Germany

2. Modeling Scott Sibole Ahmet Erdemir Craig Bennetts Randy Heydon Data Bhushan Borotikar Antonie J. van den Bogert Simulation Software Steve Maas Jeff Weiss CREDITS NIH/NIBIB R01EB009643 (model development) NIH/NIGMS R01GM083925 (FEBio) NIH/NIAMS R01AR049735 (data collection) Simbios (project hosting)

3. KNEE MODELING FOR ACL 1 Homyk et al., Comput Methods Biomech Biomed Engin, 1:1, 2011. 2 Park et al., J Biomech, 43: 2039-42, 2010. 3 Moglo and Shirazi-Adl, Knee, 10: 265-76, 2003. Injury mechanisms 1 Impingement 2 Load transmission 3 2

4. 491 EXAMPLES OF KNEE MODELING 1 Bendjaballah et al., Clin Biomech, 12: 139-48, 1997. 2 Donahue et al., J Biomech Eng, 124: 273-80, 2002. 3 Peña et al., J Biomech, 39: 1686-701, 2006. 4 Dhaher et al., J Biomech,, 43: 3118-25, 2010. 1 2 3 4

5. OPEN KNEE General purpose tibiofemoral joint model Dissemination of model/data/results for crowd- sourced large-scale population- based and specimen-specific validation

6. VALIDATION OF KNEE MODELS Joint Level Validation Tibiofemoral kinematics/kinetics Passive flexion 1 Envelope Lifelike loading Tissue Level Validation Structural Contact force/area Ligament force Material Tissue strain/stress Contact pressures 1 1 Erdemir and Sibole, ISB 2011, Brussels, Belgium.

7. VALIDATION OF KNEE MODELS Population-based data Literature on knee kinematics/kinetics 1 Literature on tissue function Specimen-specific data Simple mechanical testing Robotics testing 1 Wilson et al., J Biomech, 33: 465-73, 2000.

8. GOAL To establish the capacity of Open Knee for complete reproduction of specimen-specific anterior-cruciate ligament deformations

9. METHODS: DATA 1 Borotikar BS, Doctoral Dissertation, Cleveland State University, 2009. 2 Grood and Suntay, J Biomech Eng, 105: 136-44, 1983. Experimentation 1 Cadaver specimen used for Open Knee 100 N anterior drawer forces 0° flexion All other dofs free Measurements of ACL length DVRT (MicroStrain, Inc.) Kinematic Conventions 1 Joint rotations/translations based on Grood and Suntay convention 2

10. METHODS: MODEL Erdemir and Sibole, Open Knee User's Guide, Version 1.0.0, 2010. Bones rigid body Cartilage nearly incompressible Neo- Hookean Menisci Fung orthotropic hyperelastic horn attachments as springs Ligaments transversely isotropic hyperelastic

11. METHODS: SIMULATIONS Anterior Drawer time (s) 53 100 N Anterior Drawer Force Simulation Type Dynamic; implicit time integration Tibia BCs Fixed in space Femur BCs Prescribed flexion (0°) Other dofs free Anterior drawer forces

12. METHODS: ACL DEFORMATIONS L length of anteromedial bundle L ref length of anteromedial bundle at 0° flexion ΔL/L ref gross measure of anterior cruciate ligament L

13. RESULTS: ACL DEFORMATIONS Anterior TranslationACL Deformation

14. RESULTS: OFF-AXIS KINEMATICS TranslationsRotations

15. DISCUSSION: SUMMARY Comparison of Open Knee kinematics (translation + rotation) and ACL deformation against specimen-specific experimental data Model predicted anterior displacements are lower Model predicted ACL deformations are higher Large discrepancies in off-axis kinematics internal tibial rotation lateral translation

16. DISCUSSION: LIMITATIONS Open Knee, for anterior drawer test, does not reliably predict ACL deformations and kinematics Gross ACL deformations Representation of ACL constitutive parameters in situ strains Representation of other components ligaments menisci Approximation of coordinate system registration

17. DISCUSSION: FUTURE WORK 1 Chokhandre, et al., SBC 2012, Fajardo, Puerto Rico. 2 Dhaher, et al., J Biomech, 43: 3118-25, 2010. Acquisition of more elaborate data 1 registration imaging joint & tissue characterization Sensitivity analysis 2 Modeling abstractions Collaborative testing & development Joint Tissue

18. DISCUSSION: LONG TERM GOALS Predictive capacity for joint response tissue response Confirmed by population-based specimen-specific data for reliable decision-making Community-driven development experimentation modeling

19. DISSEMINATION http://simtk.org/home/openknee Wiki Subversion repository Release package Creative Commons Attribute Share-Alike Licensing Software Finite element analysis (free and open for academia) http://mrl.sci.utah.edu/software Scripting (free and open for all) http://www.python.org Mesh generation (proprietary) http://www.truegrid.com