www.sori.com.au the effect of graft position for a single bundle acl reconstruction – fea study...
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The effect of graft position for a single bundle ACL reconstruction – FEA Study
Ravi Sundaramurthy (B.Eng Biomedical)Dr. David Parker (FRACS)
Dr. Qing Li (PhD, University of Sydney)
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Background- Graft Placement
IsometricIsometric Minimum strain of graftMinimum strain of graft Preserves the life of the graft longestPreserves the life of the graft longest Knee biomechanics not represented Knee biomechanics not represented
AnatomicalAnatomical Placed at footprint of original ACLPlaced at footprint of original ACL Approximates knee biomechanics betterApproximates knee biomechanics better Higher failure rates, stretching etcHigher failure rates, stretching etc
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Literature Review
Several FEA models on knee Donohue et al, 2002 etc
Very few studies on ACL reconstruction using FEA models
Pena E et al, 2005*
*Pena E et al, Influence of the tunnel angle in ACL reconstructions on the biomechanics of the knee joint, Clinical Biomechanics, 2006, p508-516
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Aims
Build an accurate FE model of the knee
Analyse effect of changing ACL graft position on
Biomechanics of the knee
Stress and strain on the graft and major ligaments
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Methods
Describe what was actually done
Created a FE Model of knee using what program? How many knees did you use?
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Assumptions in the Model
Meniscus and articular cartilage not modelled
Muscles (Passive and active) not modelled
Knee is modelled in Full Extension
Ligament is modelled as linear non-viscoelastic
Pre-tensioning of ligaments and grafts not considered
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Graft Positioning
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Result Anterior Tibial Loading
190.7 N Posterior Femoral Load
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Results External Tibial Rotation
5 N.m External Torque
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LCL Stresses and Strain
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Internal Tibial Rotation
5 N.m Internal Tibial Rotation
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Internal Tibial Rotation
No ACL Loading
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Conclusion
Several trends were observed in ligament stress, strain and knee kinematics with varying graft position
An alternative method to clinical studies was used to study effect of graft position
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Future Directions
Effect of Different Flexion Angles
Model ligaments as non-linear viscoelastic
Study effect of muscles, meniscus etc
Study Double Bundle technique
Study effect of more graft materials