Design of dynamic stabilization system with stiffness similar to normal discs by topology optimization

Name: Norravich Lertviriyachit

Organization : Chulalongkorn University. Center of Excellence for Prosthetic and Orthopedic Implant

Name: Pairat Tangpornprasert

Organization : Chulalongkorn University. Center of Excellence for Prosthetic and Orthopedic Implant

Name: Chanyaphan Virulsri

Organization : Chulalongkorn University. Center of Excellence for Prosthetic and Orthopedic Implant

Email : chanyaphan.v@eng.chula.ac.th

keyword: Dynamic stabilization system

; Carbon-fiber reinforced polyether-ether-ketone (CFR-PEEK)

; Topology optimization

Abstract: Low back pain is undeniably a common spinal problem primarily caused by lumbar spine instability resulting from various disorders, ranging from tumors and herniated discs to spondylolisthesis. The gold standard treatment for this instability is the spinal fusion technique, which involves rigid fixation through pedicle screws and rods. This method allows patients to regain significant stability in their lumbar spines. However, it also carries a major drawback: the risk of adjacent segment degeneration (ASD) due to the necessary motion compensation from the adjacent spinal units. To address this issue, a dynamic stabilization system (DSS) was developed to help stabilize problematic segments while allowing motion, thus reducing the occurrence of ASD. Although state-of-the-art DSS focuses on enabling spinal motion within the neutral zone, further attention must be given to achieving a decent stiffness for the DSS. Existing DSS designs, such as Dynesys and Bioflex, mainly focused on providing motion but were too rigid to prevent ASD efficiently. Therefore, our research aimed to develop a DSS that can achieve a similar stiffness to normal lumbar discs by leveraging the advantages of carbon fiber-reinforced polyether-ether-ketone (CFR-PEEK), including strength, flexibility, and biocompatibility. Topology optimization as a tool in Ansys was utilized to obtain the initial shape of our DSS. During the optimization process, three types of moments—flexion-extension (FE), lateral bending (LB), and axial rotation (AR)—were applied as boundary conditions, with a magnitude of 6.6 Nm, to simulate physiological spinal movements. Subsequently, the initial shape underwent fine-tuned and validation to ensure that the final shape achieved the desired stiffness: kFE = 1.8 Nm/°, kLB = 2.3 Nm/°, and kAR = 8.4 Nm/°. The resulting DSS exhibited stiffness values of kFE = 2.10 Nm/°, kLB = 2.66 Nm/°, and kAR = 9.28 Nm/°, respectively. These outcomes deviated from the target of only 16.7%, 15.7%, and 10.5%, demonstrating the effectiveness of the design. However, the designed DSS manufacturing process remained challenging owing to its complicated shape

King Mongkut's University of Technology North Bangkok. Central Library

Address: BANGKOK

Email: library@kmutnb.ac.th

Created: 2024

Modified: 2024-12-17

Issued: 2024-12-17

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BibliograpyCitation : In Thai Society of Mechanical Engineers (TSME) and Chiang Mai University. The 13th TSME International Conference on Mechanical Engineering (TSME-ICoME 2023) (pp.510-518). Chiang Mai : Chiang Mai University, 2023

eng

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