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

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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.