20 February 2024
Congratulations to our Honours student Ms Vicki Cheah, on completing her Honours thesis titled “Investigation of the biomechanical properties of fixation constructs used in L5-S1 lumbar fusion spine surgeries”.
Fusion procedures involve the removal of vertebral disc and insertion of a grafted cage implant into the intervertebral space to eliminate motion. The maintenance of stability and rigidity at the fusion site during the initial 3-6 months after surgery are fundamental in obtaining successful fusion. However, there is a distinctly higher degree of mechanical load and stress applied to the L5/S1 site compared to the above segments. This makes reducing motion at this location more difficult and hence requires the use of additional fixation constructs at the fusion site. These additional fixation constructs may include an anterior plate, posterior pedicle screws or integrated screws within the cage itself. An efficient means of comparing these techniques is to use computational modelling and Finite Element analysis (FEA).
This project involved the construction of a 3D model of the Lumbosacral joint (L5/S1) of the spine to investigate the stability and rigidity of anterior and/or posterior fixation constructs used in anterior lumbar fusion surgery using FEA. Ms Cheah modelled the stand-alone interbody cage (Figure 1A), an integrated screw cage (Figure 1B) and an interbody cage with the addition of an anterior plate (Figure 1C) or pedicle screws (Figure 1D).
After application of FEA her results demonstrated that all five construct scenarios, in comparison to the intact spine (Figure 1A-1D) showed at least a 93% reduction in the range of motion, 99% reduction in strain and 88% reduction in deformation of the L5/S1 site compared to an intact spine with no cage or fixation constructs. The anterior plate demonstrated the greatest stability in all results and directions of motion, followed by the pedicle screws and integrated screws. However, the magnitude of difference between these constructs was minimal, indicating that all fixation constructs remain adequate choices for fusion of the L5/S1 site.
We are extremely proud of Ms Cheah for completing her Mechanical Engineering Final Year Honours project and have been impressed throughout her research journey with the high quality of work she has produced. Ms Cheah had this to say about her time collaborating with Neurospine Institute;
“Working with the research team at Neurospine Institute for my Honours project was an extremely rewarding experience. Comparing different implant configurations at L5-S1 using finite element analysis was an interesting and challenging project especially as I had limited prior exposure to the medical field. I am thankful for the extensive assistance and guidance provided by the team as a result. The continuous learning about my project and the broader biomedical field was consistently engaging!”
Ms Cheah will be Neurospine Institute’s second graduating Honours student and we are very much looking forward to seeing her progress through her career endeavors. If you are an Honours, Masters or PhD student looking for research projects to challenge and contribute to the contemporary world of spinal and surgical research, please contact us at research@nsiwa.com.au or call us on (08) 6147 8222.