3D-PRINTED SUPERELASTIC LATTICE-BASED STRUCTURES FOR LOAD-BEARING BIOMEDICAL APPLICATIONS

提出的研究计划旨在通过连接生物力学，机械设计，材料科学和技术领域，开发具有增强生物力学兼容性和几何一致性的基于晶格的植入物。本研究项目的应用重点是椎间笼，因为这些装置在脊柱疾病患者的生活质量中起着重要作用，目前可用的设计都没有提供令人满意的解决方案。申请人建议，具有增强生物力学和几何相容性的超弹性格基植入物将通过优化此类装置的负载分担能力和促进其安装来改善植入结果。新一代骨科植入物的开发和体外验证构成了本研究的主要创新方面。为了模拟周围骨骼的行为，保持种植体的机械强度，同时为骨骼生长提供足够的孔隙大小，该项目从结构优化和不同晶格结构候选物的建模开始。接下来，这些结构将由超弹性形状记忆合金进行3d打印，并进行静态和疲劳力学测试，以建立细胞结构的功能特性与其块状材料等效物之间的比例关系。为了避免在优化这些结构时采用反复试验的方法，将采用多尺度数值模拟方法模拟它们的超弹性行为，并将数值结果与实验观察结果进行比较。接下来，将设计和测试椎间笼原型，以模拟脊柱的生理运动：压缩、屈伸和轴向旋转。使用从患者处获得的CT文件，将原型笼进行复古设计，以适应两个典型位置（颈椎和腰椎）的椎间隙。最后，从植入物及时送到手术室的角度来看，将开发一种技术可靠且经济可行的工作流程。在这项研究中创造的知识体系将直接从椎间笼（该项目的应用重点）转移到其他承重个性化植入物应用中，即用于骨肿瘤或侵袭性软组织肉瘤后严重骨缺损置换的内假体。此外，更好地了解3D打印技术对使用性能的影响，特别是对疲劳的影响，将被广泛应用，而不仅仅局限于形状记忆合金和医疗领域。最后，该计划将有助于培养多学科（生物力学、机械设计、材料科学、冶金）的高素质人才，并吸引顶尖的本地和外国学生到ETS学习。

The proposed research program aims at developing lattice-based implants with enhanced biomechanical compatibility and geometric conformity, by bridging the fields of biomechanics, mechanical design, materials science and technology. The application focus of this research program is intervertebral cages, since these devices play a significant role in the quality of life of patients with spinal disorders, and none of the currently available designs offers a satisfying solution. The applicant suggests that superelastic lattice-based implants with enhanced biomechanical and geometrical compatibilities will improve the outcome of implantation by optimizing the load sharing capacity of such devices and facilitating their installation. The development and ex vivo validation of a new generation of orthopedic implants constitute the main innovative aspects of this research. In order to mimic the behavior of surrounding bone, and maintain the mechanical strength of an implant, while providing adequate pore size for bone ingrowth, the project starts with the structural optimization and modeling of different lattice structure candidates. Next, these structures will be 3D-printed from a superelastic shape memory alloy and subjected to static and fatigue mechanical testing in order to establish scaling relations between the functional properties of cellular structures and their bulk material equivalents. To avoid the trial-and-error approach when optimizing these structures, their superelastic behavior will be simulated using a multi-scale numerical modeling approach, and the numerical results will be compared with the experimental observations. Next, intervertebral cage prototypes will be designed and tested to simulate physiological movements of the spine: compression, flexion/extension and axial rotation. Prototype cages will be retro-engineered to fit the intervertebral spaces in two typical locations (cervical and lumbar), using CT files obtained from patients. Finally, in the perspective of just-in-time implant delivery to the operation room, a technologically reliable and economically viable workflow will be developed. The body of knowledge created during this research will be directly transposable from intervertebral cages (application focus of this program) to other load-bearing personalized implant applications, namely, endoprostheses for the replacement of critical bone defects following bone tumors or invasive soft tissue sarcomas. Furthermore, a better understanding of the impact of the 3D printing technology on the service properties, especially with respect to fatigue, will be widely applicable, and will not be limited exclusively to shape memory alloys and the medical domain. Finally, the proposed program will contribute to the multidisciplinary (biomechanics, mechanical design, materials science, metallurgy) training of highly qualified personnel and attract top-level local and foreign students to ETS.