THE ENGINEERING SIDE OF BONE DEFECT TREATMENT: A SOFTWARE TOOL FOR SURGEONS TO DESIGN PATIENT-SPECIFIC SCAFFOLDS

Bone defects caused by trauma, cancer, or infection, are problematic for surgeons and patients alike. Critical-sized bone defects will not heal over one's lifetime without (surgical) intervention. Current treatment options have significant limitations and a strong demand for clinically translatable alternatives, such as scaffold-guided bone regeneration (SGBR). Our interdisciplinary team has studied SGBR for critical-sized bone defects over the last two decades in pre-clinical trials and demonstrated successful bone regeneration in a well-characterised and validated sheep segmental defect model. These findings were recently translated into a clinical setting, and we could provide bespoke SGBR solutions for selected patients in Australia and Germany who experienced critical-sized bone defects of 10 to 34 cm. Over the years, the scaffold design process has continuously improved, but a low-cost and efficient software tool that designs these scaffolds ‘on-the-fly’ according to the surgeon's needs while readily being 3D printable remains the main challenge. A semi-automatic patient-specific SGBR design workflow (Figure 1) was developed and implemented within Rhinoceros 3D and Grasshopper (R&G) software (Robert McNeel & Associates, USA). A dedicated in-house developed plugin enabled the export of 3D print-ready models. The workflow could be quickly adapted to different bone defect scenarios via a modular setup and produced scaffold designs based on an array of pore architectures, including the Voronoi tessellation that mimics natural trabecular bone. Lastly, it allowed the surgeon to verify the designs by overlaying them on medical images of the defect. The tool was validated by applying it to four clinical case studies: a complex multi-fragmentary femoral defect (Figure 2), a bilateral femoral defect, a segmental humerus defect, and a large volume craniomaxillofacial defect. All scaffolds were designed within 90 min, and the output models were free from surface mesh errors that inhibit accurate 3D printing. The designs showed an excellent, patient-specific fit when examined both digitally and physically using 3D-printed prototypes. Our workflow successfully designs patient-specific scaffolds with real-time responsiveness. It is currently being developed into a standalone software that allows surgeons to easily and quickly provide SGBR scaffold design solutions, with minimal user interaction using a simplified interface.