TOPOLOGY OPTIMIZATION DESIGN AND MECHANICAL ANALYSIS OF A PERSONALIZED LUMBAR FUSION DEVICE

Abstract

Objective: To reduce the shielding effect caused by the large elastic modulus of metal fusion devices after osteotomy for the treatment of scoliosis. Methods: A personalized fusion device was designed using reverse engineering techniques, three-dimensional modeling, topology optimization, and finite element analysis. A finite element model of the lumbar spine after orthopedic surgery was established from an actual case. A fusion device was implanted into the lumbar spine before and after the optimized design for simulation calculations, respectively. The similarities and differences in the mechanical properties of the different fusion devices and vertebrae were compared. Based on the topological optimization of the mechanical properties of the fusion system, a lightweight fusion device was designed and the stress-shielding effect on the lumbar vertebrae was improved. Results: The topologically optimized fusion device described in the current case was 60% lighter while maintaining the strength of the fusion. After optimization, the average strain of the fusion was increased by up to 200% and the stiffness was significantly decreased. The average equivalent stress of cancellous bone was increased by up to 9.55% for the PEEK fusion device. In contrast, the topologically optimized fusion can increase the average equivalent stress of cortical bone by 5.63% and reduce the stress-masking effect of vertebrae. Conclusion: Topologically optimized titanium alloy fusion devices can significantly reduce the mass of the implant as well as reduce fusion stiffness. Additionally, a topology-optimized titanium alloy fusion device can effectively improve the stress-shielding effect of cortical bone.