• Naresh Kumar, Alathur RamakrishnanSridharanSDepartment of Orthopaedic Surgery, National University Health System, Level 11 Tower Block, 1E, Lower Kent Ridge Road, Singapore, 119228, Singapore., Keith Gerard Lopez, Niyou Wang, Sirisha Madhu, Balamurugan A Vellayappan, James Tpd Hallinan, FuhJerry Ying HsiJYHDepartment of Mechanical Engineering, National University of Singapore, #04-18 Block EA, 9 Engineering Drive 1, Singapore, 117575, Singapore., and A Senthil Kumar.
• Department of Orthopaedic Surgery, National University Health System, Level 11 Tower Block, 1E, Lower Kent Ridge Road, Singapore, 119228, Singapore. dosksn@nus.edu.sg.
• Eur Spine J. 2023 Jun 1; 32 (6): 195319651953-1965.

PurposeTo manufacture and test 3D printed novel design titanium spine rods with lower flexural modulus and stiffness compared to standard solid titanium rods for use in metastatic spine tumour surgery (MSTS) and osteoporosis.MethodsNovel design titanium spine rods were designed and 3D printed. Three-point bending test was performed to assess mechanical performance of rods, while a French bender was used to assess intraoperative rod contourability. Furthermore, 3D printed spine rods were tested for CT & MR imaging compatibility using phantom setup.ResultsDifferent spine rod designs generated includes shell, voronoi, gyroid, diamond, weaire-phelan, kelvin, and star. Tests showed 3D printed rods had lower flexural modulus with reduction ranging from 2 to 25% versus standard rod. Shell rods exhibited highest reduction in flexural modulus of 25% (~ 77.4 GPa) and star rod exhibited lowest reduction in flexural modulus of 2% (100.8GPa). 3D printed rod showed reduction in stiffness ranging from 40 to 59%. Shell rod displayed highest reduction in stiffness of 59% (179.9 N/mm) and gyroid had least reduction in stiffness of 40% (~ 259.2 N/mm). Rod bending test showed that except gyroid, other rod designs demonstrated lesser bending difficulty versus standard rod. All 3D printed rods demonstrated improved CT/MR imaging compatibility with reduced artefacts versus standard rod.ConclusionBy utilising novel design approach, we successfully generated a spine rod design portfolio with lower flexural modulus/stiffness profile and better CT/MR imaging compatibility for potential use in MSTS/other conditions such as osteoporosis. Thus, exploration of new rod designs in surgical application could enhance treatment outcome and improve quality of life for patients.© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

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