1/23DETC Design of an Interbody Fusion Implant 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 Dame Department of Aerospace and Mechanical Engineering 29 th Design Automation Conference – International 2003 DETC September 2-6, 2003 – Chicago, IL

2/23DETC Design of an Interbody Fusion Implant Content Lumbar Spine Fixation Topology Optimization Shape Optimization Results and Conclusions

3/23DETC Design of an Interbody Fusion Implant The Spinal Column [

4/23DETC Design of an Interbody Fusion Implant Disc Problems [

5/23DETC Design of an Interbody Fusion Implant PLIF – Posterior Lumbar Interbody Fusion Fusion with spinal instrumentation [Virginia Spine Institute]

6/23DETC Design of an Interbody Fusion Implant ALIF – Anterior Lumbar Interbody Fusion [ Interbody cage fusion

7/23DETC Design of an Interbody Fusion Implant New fusion procedure Implant Bone Graft

8/23DETC Design of an Interbody Fusion Implant Design procedure Topology optimization Shape optimization

9/23DETC Design of an Interbody Fusion Implant Topology optimization Implant Bone Graft 2064 design variables [FEBM / GENESIS] Design Domain

10/23DETC Design of an Interbody Fusion Implant Vertebra model Cortical boneCancellous bone Cartilage Design domain [Goel and Weinstein, 2000]

11/23DETC Design of an Interbody Fusion Implant Load conditions [Rohlmann et al, 2001] Flexion15.0 Nm Extension 5.0 Nm Lateral bending 7.5 Nm Compressive preload 400 N

12/23DETC Design of an Interbody Fusion Implant Lateral bending + + Left & right lateral bending 7.5 Nm

13/23DETC Design of an Interbody Fusion Implant Flexion and extension + + Flexion 15.0 Nm Extension 5.0 Nm

14/23DETC Design of an Interbody Fusion Implant The topology optimization problem

15/23DETC Design of an Interbody Fusion Implant The topology optimization problem

16/23DETC Design of an Interbody Fusion Implant Optimum topologies

17/23DETC Design of an Interbody Fusion Implant Spline approximation

18/23DETC Design of an Interbody Fusion Implant Domains and perturbation vectors 18 domains18 design variables

19/23DETC Design of an Interbody Fusion Implant The shape optimization problem

20/23DETC Design of an Interbody Fusion Implant Shape optimization Flexion Extension Left lateral bending Right lateral bending

21/23DETC Design of an Interbody Fusion Implant Shape optimization

22/23DETC Design of an Interbody Fusion Implant Results Stress analysis Designs

23/23DETC Design of an Interbody Fusion Implant 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

25/23DETC Design of an Interbody Fusion Implant Shape optimization Flexion ExtensionLateral bending