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Bioresorbable Magnesium-Based Bone Fixation Hardware: Alloy Design, Post-Fabrication Heat Treatment, Coating, and Modeling

Ibrahim, Hamdy, Ibrahim

Abstract Details

2017, Doctor of Philosophy, University of Toledo, Mechanical Engineering.
Magnesium (Mg) alloys have shown biodegradable properties that make them appealing for various biomedical applications. Mg corrodes gradually in the body and it has low density and modulus of elasticity, close to that of the bone. However, the fast rate of degradation and low strength are the main challenges that hinder the use of Mg alloys for bone fixation applications. This dissertation provides a comprehensive review of the literature on the most promising Mg alloys and possible techniques to improve their mechanical and corrosion properties. The main goal of this research is to develop bioresorbable Mg-based fixation hardware with adequate strength and acceptable degradation rate using nontoxic alloying elements. To this end, finite element analysis, design of experiments, and novel post-fabrication techniques (heat treatment and coating) were combined towards patient-specific biodegradable fixation hardware. As the initial step, various Mg-Zn-Ca-based alloys, as the most biocompatible alloys, were designed and fabricated. Heat treatment, as a favorable post-fabrication process for parts produced in their final shape, was investigated to understanding the effect of heat treatment on the corrosion behavior, microstructural characteristics, and mechanical properties of Mg-Zn-Ca-based alloys. Heat treatment was found to be a practical approach to significantly reduce the corrosion rate and to enhance the corrosion behavior of these alloys. Aging Mg-Zn-Ca-based alloys that contain low Zn contents (between 1.2-2 wt.%) and a small amount of Mn (0.5 wt.%) at 200 °C for 2-5 hours was found to result in the best mechanical and corrosion properties. Despite the enhanced corrosion properties of the heat-treated alloys, biocompatible coatings are essential to protect the device during the healing period of bone, during which the implant is under maximum loads. Such coating should enable delaying the degradation of Mg-based fixation hardware to maintain the mechanical integrity needed during bone healing. A biocompatible composite coating was prepared using an in-house micro arc oxidation (MAO) setup and a sol-gel (layer-by-layer) process. The results showed that the MAO/sol-gel composite coating significantly enhanced the corrosion resistance of the heat-treated Mg alloys. As the first application, mandibular reconstructive surgery (MRS) was chosen. FEA study of the biomechanical performance of Mg-based fixation hardware had shown promising results in providing stability after implantation. The results of this FEA study, alloy development, heat treatment, and coating studies are useful tools to design and evaluate a biodegradable fixation hardware for Cranio-Maxillofacial surgical applications such as MRS.
Mohammad Elahinia (Committee Chair)
Arunan Nadarajah (Committee Member)
Efstratios Nikolaidis (Committee Member)
Sarit Bhaduri (Committee Member)
Matthew Franchetti (Committee Member)
166 p.

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Citations

  • Ibrahim, Ibrahim, H. (2017). Bioresorbable Magnesium-Based Bone Fixation Hardware: Alloy Design, Post-Fabrication Heat Treatment, Coating, and Modeling [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1503678544356525

    APA Style (7th edition)

  • Ibrahim, Ibrahim, Hamdy. Bioresorbable Magnesium-Based Bone Fixation Hardware: Alloy Design, Post-Fabrication Heat Treatment, Coating, and Modeling. 2017. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1503678544356525.

    MLA Style (8th edition)

  • Ibrahim, Ibrahim, Hamdy. "Bioresorbable Magnesium-Based Bone Fixation Hardware: Alloy Design, Post-Fabrication Heat Treatment, Coating, and Modeling." Doctoral dissertation, University of Toledo, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1503678544356525

    Chicago Manual of Style (17th edition)