1. Open Knee: Capacity to Reproduce Passive Joint Kinematics Ahmet Erdemir and Scott Sibole Computational Biomodeling Core Department of Biomedical Engineering Cleveland Clinic July 6, 2011 ISB 2011, Brussels, Belgium

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. PURPOSES OF KNEE MODELING Joint and tissue functions Pathological impacts Injury mechanisms Surgical interventions Gardiner and Weiss, J Orthop Res, 21: 1098-106, 2003. Park et al., J Biomech, 43: 2039-42, 2010. Vaziri et al., Annals of Biomed Eng, 36: 1335-44, 2008. Saarakkala et al., Osteoarthritis and Cartilage, 18: 73-81, 2010. MCL function ACL impingement Osteoarthritis Menisectomy

4. 455 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, Epub ahead of print, 2010. 1 2 3 4

5. VALIDATION OF KNEE MODELS Joint Level Validation Tibiofemoral kinematics/kinetics Passive flexion Envelope Lifelike loading Tissue Level Validation Structural Contact force/area Ligament force Material Tissue strain/stress Contact pressures

6. VALIDATION OF KNEE MODELS Population-based data Literature on knee kinematics/kinetics Literature on tissue function Specimen-specific data Simple mechanical testing Robotics testing

7. GOALS To establish the capacity of Open Knee for complete reproduction of population-specific passive joint response To disseminate model/data/results for crowd-sourced large- scale population-based/specimen-specific validation at multiple spatial scales

8. 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

9. METHODS: DATA 1 Wilson et al., J Biomech, 33: 465-73, 2000. 2 Grood and Suntay, J Biomech Eng, 105: 136-44, 1983. Experimentation 1 15 cadaver specimens Tibia fixed; femur moving Flexion (0° – 100°) prescribed All other dofs free Kinematic Conventions 1 Joint rotations based on Grood and Suntay convention 2 Translations described displacement of posterior tibial insertion of ACL

10. METHODS: SIMULATIONS Passive Knee Flexion time (s) 2.5 100° Knee Flexion Simulation Type Dynamic; implicit time integration Tibia BCs Fixed in space Femur BCs 100° prescribed flexion Other dofs free

11. RESULTS Rotations Internal rotation (up to ~60° flexion) Abduction Translations Posterior (up to ~50° flexion) Proximal Medial (up to ~50° flexion)

12. RESULTS

13. DISCUSSION: SUMMARY Complete passive kinematics response of Open Knee (translation + rotation) was compared against population- based experimental data Passive kinematics was coupled to flexion Proximal-distal translation predictions were not in agreement Open Knee exhibited deviations from experimental data in high flexion angles

14. DISCUSSION: LIMITATIONS Constraint moments (to prescribe flexion angles) were not assessed Population-based (not specimen-specific) data were utilized Model exhibited inherent limitations such as lack of in situ ligament strain Correct joint response predictions may not indicate adequate tissue stress/strain predictions

15. DISCUSSION: FUTURE WORK 1 Blankevoort, et al., J. Biomech, 21: 705-20, 1988. 2 Borotikar BS, Doctoral Dissertation, Cleveland State University, 2009. Sensitivity to tissue properties Validation against envelope of knee joint population-based data 1 Validation against envelope of knee joint specimen-specific data 2 Tissue level validation Collaborative testing & development

16. 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