Femtosecond laser ablation of bovine cortical bone

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Ultrafast lasers are extremely promising tools for minimally-invasive orthopedic surgery, but the influence of femtosecond laser ablation on the surface topography, structure and composition of bone was scarcely investigated up to now. The purpose of this work is to study this influence in vitro, using bovine cortical bone as a model. The ablation tests were performed in air and in dry conditions and under flowing water, with a 500 fs pulse duration laser (1030 nm wavelength) using fluences from 0.55 to 2.18 J/cm2 and pulse frequencies between 50 and 3000 Hz. The results show that when processing is carried out in dry conditions and with pulse repetition rates up to 50 Hz, the structure of the remaining tissue is preserved and the only compositional changes detected are a slight reduction of the organic material content and a partial recrystallization of hydroxyapatite in the most superficial region of the samples. When the laser pulse frequency is increased to 2 kHz, the organic matter content at the samples’ surface decreases further and slight surface carbonization occurs. On the contrary, no compositional alterations were observed when ablation was performed under flowing water. The results suggest that ablation occurred by a combination of thermal and electrostatic mechanisms, the first explaining the thermal effects observed. This work confirms that femtosecond lasers are a viable alternative to mechanical tools for delicate orthopaedic surgeries, where small amounts of bone must be cut or removed with negligible damage. Water cooling allows high pulse frequencies to be employed and, consequently, higher tissue removal rates to be achieved.Ultrafast lasers are extremely promising tools for minimally-invasive orthopedic surgery, but the influence of femtosecond laser ablation on the surface topography, structure and composition of bone was scarcely investigated up to now. The purpose of this work is to study this influence in vitro, using bovine cortical bone as a model. The ablation tests were performed in air and in dry conditions and under flowing water, with a 500 fs pulse duration laser (1030 nm wavelength) using fluences from 0.55 to 2.18 J/cm2 and pulse frequencies between 50 and 3000 Hz. The results show that when processing is carried out in dry conditions and with pulse repetition rates up to 50 Hz, the structure of the remaining tissue is preserved and the only compositional changes detected are a slight reduction of the organic material content and a partial recrystallization of hydroxyapatite in the most superficial region of the samples. When the laser pulse frequency is increased to 2 kHz, the organic matter content at the sam...