A novel flexible-structured saw blade for bone cutting: reducing ploughing and promoting chip evacuation

Oscillating bone sawing is widely employed in orthopedic surgery due to its ability to achieve precise bone resection with minimal damage to surrounding soft tissues. However, conventional saw blades with large negative rake angles often induce excessive ploughing forces, elevated temperatures, poor chip evacuation, accelerated tooth tip wear, and crack formation in bone tissue. While trajectory and vibration-assisted strategies have been explored, their reliance on complex mechanical systems limits clinical adoption. In this study, a novel saw blade with an embedded flexible structure is proposed, which passively adjusts the depth of cut through elastic deformation of the flexible structure. This design offers two key advantages: (1) when cutting with a negative rake face, the flexible tooth adaptively reduces the actual depth of cut, thereby reducing ploughing forces; and (2) when cutting with a positive rake face, periodic elastic deformation induces passive low-frequency vibrations, promoting shear crack formation and transforming continuous, spiral-like chips into fine, needle-like fragments, thereby improving chip evacuation. Multi-tooth sawing experiments confirmed that the proposed blade reduced sawing forces by 56.4 % in the feed direction and 36.7 % in the oscillation direction, suppressed peak cutting temperature to 43.3 °C (below the 47 °C threshold for cell damage), and significantly decreased tooth tip wear and groove wall cracking. These results demonstrate the effectiveness of the proposed structure as a compact, mechanically simple solution that complements motion-based strategies, enhancing cutting performance and adaptability in bone cutting applications.