Femtosecond lasers for high-precision orthopedic surgery.

Laser micromachining with ultrashort pulses has shown great promise for clean, safe surgical treatment of bone tissue. However, comparisons of performance and development of "best practice" have been hampered by the difficulty of comparing results across a wide variety of experimental approaches and under surgically irrelevant conditions (e.g., dried, dead bone). Using a femtosecond (fs) pulsed laser system (τ = 140 fs, repetition rate = 1 kHz, λ = 800 nm), a comprehensive study of femtosecond laser microsurgery using the standard metrics of laser micromachining (ablation threshold, incubation effects, ablation rates, effect of focal point depth within the material and heat affected zone (HAZ)) was conducted on live, freshly harvested bovine and ovine cortical bone. Three important points of optimism for future implementation in the surgical theatre were identified: (1) the removal of material is relatively insensitive to the focal point depth within the material, removing the need for extreme depth precision for excellent performance; (2) femtosecond laser ablation of fresh bone demonstrates very little incubation effect, such that multiple passes of the laser over the same region of bone removes the same amount of material; and (3) the complete absence of collateral damage, heat- or shock-induced, on both the macro- and microscopic scales can be achieved readily, within a broad parameter range. Taken together, these results indicate a handheld or robotic deployed fiber laser platform for femtosecond laser microsurgery is a very viable prospect.