Ultrafast laser bone ablation towards high surgical speeds and clinically relevant operation times for spine...

Recent advancements in ultrafast laser ablation technology redefine surgical precision while minimizing thermal damage, offering a promising alternative to traditional methods. However, the slow material removal rates (MRRs) have hindered clinical adoption. Addressing this challenge, we present a compact fiber-based laser delivery system, exhibiting an 82-fold increase in MRR compared to previous femtosecond laser probes. The system leverages a hollow-core Kagome fiber to deliver 10 ps laser pulses with high transmission efficiency and minimal nonlinear effects, even at high peak powers. The system distributes ultrashort pulses utilizing a piezo-scanned Lissajous-based beam steering mechanism onto the target surface over a larger field-of-view (FOV), enabling the scope for easy scalability of the system to a miniaturized probe. Drawing insights from our prior work, the focusing optics were carefully selected to deliver fluence three times the ablation threshold. An optimal combination of FOV size, translation speed, and repetition rate was identified, enabling clean ablations (devoid of carbonization) even at maximum laser power. We achieved a maximum MRR of 10.7 mm³/min with 8.8 W of laser power at 333 kHz, validating our hypothesis that high MRR can be achieved by ablating at high average powers over a large FOV with fast scanning of a large spot size. Numerical simulations further suggest that MRR up to 30 mm³/min can be achieved through increased repetition rates, expanded FOVs, and high translation speeds, defining an optimal parameter space for future probe designs. To validate the clinical relevance of high MRR, experiments were conducted to create deep bone incisions over a 3×3 mm² area within a clinically relevant timeframe. An ablation depth of ∼3 mm was achieved in ∼2 minutes without auxiliary cooling mechanisms. Scanning electron microscopy (SEM) of the deep incisions confirmed the preservation of healthy bone tissue, with clear evidence of canaliculi along the slopes and at the bottom surface of the ablated region. This study outlines a clear pathway toward developing a high-performance, miniaturized surgical probe with significant potential for spinal decompression surgery and other clinical applications, representing a transformative tool for future surgical precision.