A Synergistic Patient-Specific Approach for Enhanced Spinal Fixation Using a Novel Flexible Pedicle Screw and a Complementary Steerable Drilling Robotic System

Objective: Current spinal fixation (SF) techniques face screw loosening and pullout challenges in osteoporotic patients. This can be attributed to conventional rigid pedicle screws (RPS) being forced to fixate along a constrained linear trajectory into low bone mineral density (BMD) areas of the vertebral body. This study proposes a synergistic patient-specific approach that integrates a steerable drilling robotic system with a novel Flexible Pedicle Screw (FPS) to enhance SF procedures by enabling curved screw fixation. Methods: A patient-specific framework and synergistic design flowchart were developed to guide the synergistic design of the previously proposed Concentric Tube-Steerable Drilling Robot (CT-SDR) and the FPS. After, the novel FPS is designed based on critical design features and its design is validated using Finite Element Analysis (FEA). The FPS is then fabricated via Direct Metal Laser Sintering (DMLS). The FPS's morphability and self-tapping capability were experimentally assessed in Sawbones phantoms drilled by the CT-SDR system. Results: The FPS successfully morphed to fixate in curvilinear paths, demonstrating effective morphability and self-tapping in simulated bone. Conclusion: By enabling a flexible, patient-specific approach to pedicle screw fixation, the FPS and CT-SDR system address key limitations of current SF procedures. This method enhances screw anchorage and fixation strength in osteoporotic vertebrae. Significance: This work presents a transformative approach to SF, with potential clinical applications in improving surgical outcomes for osteoporotic patients. The integration of robotic-assisted drilling and flexible implants could significantly reduce fixation failure rates, advancing orthopedic and spinal surgical practices.