title: Biomechanical investigation into the structural design of porous additive manufactured cages using numerical and experimental approaches.
abstract: Traditional solid cages have been widely used in posterior lumbar interbody fusion (PLIF) surgery. However, solid cages significantly affect the loading mechanism of the human spine due to their extremely high structural stiffness. Previous studies proposed and investigated porous additive manufactured (AM) cages; however, their biomechanical performances were analyzed using oversimplified bone-implant numerical models. Thus, the aim of this study was to investigate the outer shape and inner porous structure of the AM cages. The outer shape of the AM cages was discovered using a simulation-based genetic algorithm; their inner porous structure was subsequently analyzed parametrically using T10-S1 multilevel spine models. Finally, six types of the AM cages, which were manufactured using selective laser melting, were tested to validate the numerical outcomes. The subsidence resistance of the optimum design was superior to the conventional cage designs. A porous AM cage with a pillar diameter of 0.4mm, a pillar angle of 40°, and a porosity of between 69% and 80% revealed better biomechanical performances. Both the numerical and experimental outcomes can help surgeons to understand the biomechanics of PLIF surgery combined with the use of AM cages.
authors.affiliation: Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan, ROC.
authors.forename: Pei-I
authors.initials: PI
authors.lastname: Tsai
authors.affiliation: Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106, Taiwan, ROC. Electronic address: hsucc@mail.ntust.edu.tw.
authors.forename: Ching-Chi
authors.initials: CC
authors.lastname: Hsu
authors.affiliation: Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan, ROC.
authors.forename: San-Yuan
authors.initials: SY
authors.lastname: Chen
authors.affiliation: Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan, ROC.
authors.forename: Tsung-Han
authors.initials: TH
authors.lastname: Wu
authors.affiliation: Biomedical Technology and Device Research Laboratories, Industrial Technology Research Institute, Hsinchu 310, Taiwan, ROC.
authors.forename: Chih-Chieh
authors.initials: CC
authors.lastname: Huang
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology*; D003198:Computer Simulation; D020342:Finite Element Analysis; D006801:Humans; D016268:Internal Fixators; D008159:Lumbar Vertebrae / Q000502:physiology / Q000601:surgery; D008954:Models, Biological; D016062:Porosity; D011474:Prosthesis Design; D013123:Spinal Fusion / Q000295:instrumentation*
keywords: Additive manufactured cage; Cage stress; Disc stress; Finite element analysis; Intersegmental rotation