1/23DETC 2003 - Design of an Interbody Fusion Implant Optimum Topology and Shape Design of an...

DETC 2003 - Design of an Interbody Fusion Implant 1/23

Optimum Topology and Shape Design of an Interbody Fusion Implant for Lumbar Spine Fixation

Andrés Tovar, Shawn E. Gano, John E. Renaud and James J. Mason

University of Notre DameDepartment of Aerospace and Mechanical Engineering

29th Design Automation Conference – International 2003 DETC September 2-6, 2003 – Chicago, IL

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Content

• Lumbar Spine Fixation

• Topology Optimization

• Shape Optimization

• Results and Conclusions

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The Spinal Column

[http://www.spineuniverse.com]

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Disc Problems

[http://www.spineuniverse.com]

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PLIF – Posterior Lumbar Interbody Fusion

Fusion with spinal instrumentation

[Virginia Spine Institute]

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ALIF – Anterior Lumbar Interbody Fusion

[http://www.spineuniverse.com]

Interbody cage fusion

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New fusion procedure

ImplantBone Graft

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Design procedure

•Topology optimization

•Shape optimization

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Topology optimization

ImplantBone Graft

2064 design variables

[FEBM / GENESIS]

Design Domain

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Vertebra model

Cortical boneCancellous bone

Cartilage

Design domain

[Goel and Weinstein, 2000]

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Load conditions

[Rohlmann et al, 2001]

• Flexion 15.0 Nm• Extension 5.0 Nm• Lateral bending 7.5 Nm• Compressive preload 400 N

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Lateral bending

+

+

Left & rightlateral bending

7.5 Nm

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Flexion and extension

+

+

Flexion15.0 Nm

Extension5.0 Nm

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The topology optimization problem

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The topology optimization problem

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Optimum topologies

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Spline approximation

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Domains and perturbation vectors

18 domains 18 design variables

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The shape optimization problem

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Shape optimization

Flexion

Extension

Left lateral bending

Right lateral bending

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Shape optimization

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Results

Stress analysis Designs

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Summary and Conclusions

• An optimum geometry for a new interbody fusion implant is obtained using topology and shape optimization.

• The topology optimization minimizes strain energy subject to a mass fraction constraint.

• The shape optimization minimizes mass subject to a maximum von Mises stress constraint (maximizes volume available for bone graft material).

• A total volume fraction of 66% is available for the bone graft.

Thank you

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Shape optimization

Flexion Extension Lateral bending