Design and manufacture of patient specific orthopaedic implants using selective laser melting (SLM) technology
Creators: name: SHIDID, Darpan
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400308
subject: Medical devices
classificationCode: 401402
subject: CAD/CAM systems
classificationCode: 401408
subject: Manufacturing processes and technologies (excl. textiles)
classificationCode: 401799
subject: Mechanical engineering not elsewhere classified
classificationCode: 490304
subject: Optimisation

description: Osteosarcoma is a type of malignant bone cancer, mainly occurring in children and young adults in primary form. Due to the aggressive growth of the tumour, treatment plans often involve surgical intervention and stabilization using various implants depending on the scope of the surgery. These implants are typically not customized for the individual patient, potentially causing stiffness mismatch between the implant and the surrounding bone. This stiffness mismatch results in stress shielding, which causes bone resorption and subsequent implant loosening. Recent advances in medical imaging and manufacturing science have enabled the production of complex structures with the potential to enhance the properties of orthopaedic tools and implants. Additive manufacturing (AM) is one such technology which refers to methods that generate three-dimensional structures layer by layer. AM processes are not subject to the constraints associated with traditional manufacturing methods, and provide significant opportunities for the design of novel geometries and complex lattice structures that enhance strength-to-weight ratio in comparison to traditional manufacturing methods. However, the design of such structures requires a specific skill set and expertise in handling various optimization platforms. The aim of this research is to develop Design For Additive Manufacture (DFAM) tools to assist in the implementation of a just-in-time surgical concept; whereby patient-specific, orthopaedic AM implants, are designed, manufactured and implanted within the time constraints of a single surgical procedure. In this thesis, various design algorithms are proposed and validated for the use in orthopaedic AM implant design. The proposed algorithms provide DFAM tools that are clinically useful to the just-in-time surgical concept; for example: the proposed DICOM based methods of conformal lattice generation require a fraction of the computational effort of current commercially available tools; and, the structural optimisation tools developed in this research yield equivalent results to Finite Element (FE) based structural optimisation methods, however, are in the order of 20 times more rapid. The mechanical behaviour of the optimized lattice structures developed in this research is studied numerically and experimentally, resulting in novel insights into the response of AM lattice structures. This research enables the automated generation of compliant lattice implants that are conformal to the resected bone tissue, and: achieve a recovery of approximately 85% of the initial load bearing capacity of the affected region, and display a stiffness response that is statistically indistinguishable from that of the surrounding bone tissue.