Abstract
Laser osteotomy offers high precision and contact-free bone cutting but remains limited by slower cutting speeds and shallower ablation depths compared to mechanical tools. In this study, we systematically investigated the influence of spatial beam intensity distribution on bone ablation performance by comparing Er:YAG laser with tophat and Gaussian intensity distribution under identical operating conditions. Using bovine femur cortical bone and optimized water–air cooling, the tophat intensity distribution achieved a maximum ablation depth of 44.51 mm and a maximum average material removal rate of 0.42 mm\(^{3}\)/s, outperforming the Gaussian intensity distribution (26.51 mm, 0.24 mm\(^{3}\)/s). In dry surface ablation, the tophat profile reached 1.58 mm\(^{3}\)/s±0.04 mm\(^{3}\)/s, though with increased carbonization. Compared to previously reported Er:YAG outcomes under optimized ablation conditions, the cutting depth achieved in this work represents more than a twofold improvement, bringing performance close to the planar cut dimensions required during distal femur resurfacing of a total knee arthroplasty (TKA). Scanning electron microscopy and Raman analyzes confirmed minimal compositional change after laser ablation, indicating minimal thermal damage. A steady-state model was utilized to characterize the ablation process and determine the theoretical maximum ablation depth. These findings demonstrate clear ex vivo improvements by using a tophat profile in Er:YAG systems, which have the potential for clinical adoption.
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Data availability
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.
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Acknowledgements
The authors acknowledge the contributions of Dr. Georg Schulz for CT measurements, training, and analysis. Prof. Dr. Bert Müller and Dr. Iwan Jerjen for SEM imaging, sample preparation, measurement training, and data analysis. Special thanks to Prof. Elia Marin from Kyoto Institute of Technology for his feedback regarding the Raman spectra. Thanks to Leya Pauly and Vinamrata Bhardwaj for their careful proofreading of the sentences. The manuscript was revised using AI tools such as Grammarly for grammar correction.
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This project was co-funded by the Werner Siemens Foundation as part of the MIRACLE project and Innosuisse – Swiss Innovation Agency under project number 112.465 IP-LS, titled LASER-Blade.
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M.L. performed the experimental study, performed the analyses throughout the study, and prepared the manuscript. A. H. supported and advised on data analysis and manuscript organization and particularly contributed to the ablation profile investigation approach. D.B. participated in the supervision of the study and the revision of the manuscript. D.W. supervised the project timeline and provided significant input on the experimental methods. K.G. contributed to the conceptual study and provided input in the study planning. N.F. provided insight on the medical expectations and contributed to the conceptualization. G.R. supported the data analysis and revised the paper. P.C. contributed to the conceptualization of the study, reviewed the data analysis, and contributed to the organization of the manuscript. F.C. conceptualized the research project and provided guidance on the methodology and overall research direction. She has contributed to data analysis, manuscript organization, and preparation. All authors reviewed and approved the final manuscript. The authors declare no conflict of interest.
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All experimental samples were obtained from a local supplier. The materials consisted solely of ex vivo animal skeletal tissues, and no live animals or human participants were involved. Therefore, no ethical approval or informed consent was required.
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Liu, M., Hamidi, A., Blaser, D. et al. Influence of laser beam intensity profile on deep bone ablation in laser osteotomy. Sci Rep (2026). https://doi.org/10.1038/s41598-026-37117-6
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DOI: https://doi.org/10.1038/s41598-026-37117-6
