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Geometric Design Optimization of a Titanium Tilting Suture Anchor

Salmani Mehrjerdi, Mohammad Javad | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57772 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Farahmand, Farzam; Movahhedy, Mohammad Reza
  7. Abstract:
  8. Suture anchors are implants used for reattaching torn soft tissues to bone. Tilting anchors, a subtype of suture anchors, not only maintain the features of conventional suture anchors but can also be manufactured via 3D printing with a porous surface, enabling bone ingrowth and thus ensuring secure, long-term fixation. Additionally, these anchors can achieve fixation beneath the cortical bone layer, making them effective for secure attachment in areas of low bone density. Despite these advantages, limited research exists on this type of anchor, particularly regarding its performance and strength. One of the most influential factors in suture anchor strength is the method of fixation within the bone, which depends on the anchor's geometry, material, and bone quality. This study aimed to optimize a newly designed titanium tilting suture anchor. To achieve this, a patient-specific bone model with three levels of bone density was developed using voxel-based modeling and QCT scan images, providing a suitable foundation for analyzing the anchor's performance. Subsequently, a parametric study was conducted to assess the impact of various geometric parameters of the anchor on its performance, including displacement and rotation during the implantation phase, fixation stiffness, and displacement under a 150N load during the pull-out phase, to gain a deeper understanding of how geometric parameters affect the biomechanical efficiency of the anchor. The parametric study showed that the proximal fillet radius, center of mass location horizontally and vertically, and friction coefficients in the distal and proximal sections significantly impact the anchor’s performance. Response surface method (RSM) was employed to optimize the anchor for each level of high, medium, and low bone density. Results showed that the optimized anchor outperformed the initial design across each density level, achieving improvements in displacement at 40N force by 22.31%, 9.86%, and 12.09%; in rotation by 12.35%, 14%, and 17.86%; in stiffness by 29.71%, 33.38%, and 79.94%; and in displacement at 150N force by 22%, 12.15%, and 21.45%, respectively, for high, medium, and low bone densities. Finally, to validate the findings, an experimental test was conducted on 10 human humerus bone samples, involving the application of a 40N implantation force, two cyclic loading phases, and a pull-out force. The experimental results indicated that the optimized anchor demonstrated a significant improvement in stiffness (p-value < 0.05) compared to the initial anchor (177.94 ± 42.1 N/mm vs. 125.21 ± 60.38 N/mm), while maintaining and enhancing other evaluated parameters
  9. Keywords:
  10. Finite Element Method ; Parametric Study ; Experimental Test ; Patient-Specific Modeling ; Patient-Specific Bone Model ; Elastoplastic Properties ; Voxel-Based Model

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