1/24OPTI Design of an Interbody Fusion Implant Optimum Topology and Shape Design of an Interbody Fusion Implant for Lumbar Spine Fixation Andrés Tovar, John E. Renaud and James J. Mason University of Notre Dame Department of Aerospace and Mechanical Engineering Eight International Conference on Computer Aided Optimum Design of Structures - OPTI2003 May , 2003

2/24OPTI Design of an Interbody Fusion Implant Content The Spinal Column Phase 1 – Topology Optimization Phase 2 – Shape Optimization Results, Summary and Conclusions

3/24OPTI Design of an Interbody Fusion Implant The Spinal Column

4/24OPTI Design of an Interbody Fusion Implant [Spineuniverse] The Spinal Column Disc problems

5/24OPTI Design of an Interbody Fusion Implant [Katz, 1995] CountryBack surgery rate per 100,000 inhabitants USA158 The Netherlands115 Sweden52 Great Britain30 The Spinal Column Some facts

6/24OPTI Design of an Interbody Fusion Implant The Spinal Column Fusion with instrumentation [Virginia Spine Institute] PLIF – Posterior Lumbar Interbody Fusion

7/24OPTI Design of an Interbody Fusion Implant The Spinal Column Interbody cage fusion [Spineuniverse] ALIF – Anterior Lumbar Interbody Fusion

8/24OPTI Design of an Interbody Fusion Implant The Spinal Column New fusion procedure Implant Vertebra Implant Bond Graft

9/24OPTI Design of an Interbody Fusion Implant Topology Optimization [Belegundu, 1999]

10/24OPTI Design of an Interbody Fusion Implant Topology Optimization Design domain [FEBM / GENESIS] 2064 design variables

11/24OPTI Design of an Interbody Fusion Implant Topology Optimization Vertebra model Cortical bone Cancellous bone Cartilage Design domain [Goel and Weinstein, 2000]

12/24OPTI Design of an Interbody Fusion Implant Topology Optimization Load conditions [Rohlmann et al, 2001] Flexion15.0 Nm Extension 5.0 Nm Lateral bending 7.5 Nm

13/24OPTI Design of an Interbody Fusion Implant Topology Optimization Lateral bending + + Left & right lateral bending 7.5 Nm

14/24OPTI Design of an Interbody Fusion Implant Topology Optimization Flexion and extension + + Flexion 15.0 Nm Extension 5.0 Nm

15/24OPTI Design of an Interbody Fusion Implant Topology Optimization The optimization problem [Bendsøe & Sigmund, 1999]

16/24OPTI Design of an Interbody Fusion Implant Topology Optimization The optimization problem

17/24OPTI Design of an Interbody Fusion Implant Topology Optimization Optimum topologies

18/24OPTI Design of an Interbody Fusion Implant Topology Optimization Spline approximation

19/24OPTI Design of an Interbody Fusion Implant Shape Optimization [GENESIS]

20/24OPTI Design of an Interbody Fusion Implant Shape Optimization Domains and perturbation vectors 18 domains18 design variables 444 elements

21/24OPTI Design of an Interbody Fusion Implant Shape Optimization The optimization problem

22/24OPTI Design of an Interbody Fusion Implant Shape Optimization Optimum shape Initial shapeOptimum shape

23/24OPTI Design of an Interbody Fusion Implant Results Stress analysis Designs

24/24OPTI 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 minimize strain energy subject to a mass fraction constraint for 2064 design variables. The shape optimization minimize mass subject to a maximum von Mises stress constraint for 18 design variables. A total volume fraction of 60% (respect to the original design volume) is available for the bone graft.