Femtosecond laser processing of bone tissue has shown great potential for osteotomy procedures where high precision cutting and the preservation of bone tissue functions are of primary importance. Nonetheless, the ablation rates related to this kind of process still remain too low for this technology to be exploitable in a real surgical procedure. Moreover, the strong dependence of the process outcomes from factors such as the processing environment, the type of pre-processing and post-processing treatment of the bone tissue, the species of the processed animal and the bone part itself, stall the full development and advancement of this technique. This study highlights the key role of the anatomical region (femur, tibia, etc.) and species (pig, chicken, etc.) of the investigated bone tissue samples to provide a solid reference on the impact of the choice of types of samples on laser ablation studies of bone tissue. Results show that it is essential to choose the best animal model for a specific case study, which depends to a large extent on the objectives of the research subject. There are no perfect animal models: the selection of one animal model is often associated with its similarity to the human model because the goal is the validation of experiments in clinical setting. However, most studies do not take these variabilities into account in their conclusions.
Femtosecond laser processing is well known because of the achievable unparalleled precision with minimized thermal effects on most materials, making this technology competitive for its clinical use on living tissue. Nevertheless, femtosecond laser processing often requires an optimization of the parameters in order to increase the ablation rate which remains too limited compared to CW or QCW lasers. This study identifies an optimized set of process parameters (wavelength, temperature, bone hydration) for efficiently ablating bone tissue. Three different absorption regimes are studied using fs laser sources centered at wavelengths of 1030 nm, 515 nm and 343 nm. The thermal effects generated by the interaction of the fs laser and the bone were analyzed using a thermal camera and thermocouples with different cooling methods (water and air). Our results highlight (i) the significant capacity of the visible wavelength (515 nm) to ablate bone tissue with a maximum value of 0.66 mm3/s on pork femurs and that (ii) the use of water for cooling the sample is the most effective method of cooling and reduce thermal propagation without impacting the ablation rate. This study also raises awareness about the role of the anatomical region (femur, tibia, etc.) and species (pig, chicken, etc.) of the investigated bone tissue samples which may induce significant differences in ablation efficiency.
Nowadays Er:YAG lasers are employed for bone surgery because of their emission wavelengths of 2.94µm which allows for optimization of material removal rate. Nevertheless, high degrees of tissue carbonization are unavoidable and prevent the process of tissue regeneration. In this work, a femtosecond source with a pulse duration of 350fs was employed to carry a comparative study on ablation efficiency and quality at wavelengths of 1030nm and 515nm. Laser-treated bones were analyzed by optical profilometry, SEM and EDX. Results show that on optimization of the process parameters is necessary to achieve an optimal quality of ablation without tissue carbonization.
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