Influence of laser beam intensity profile on deep bone ablation in laser osteotomy

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[Formula: see text]/s, outperforming the Gaussian intensity distribution (26.51 mm, 0.24 mm[Formula: see text]/s). In dry surface ablation, the tophat profile reached 1.58 mm[Formula: see text]/s±0.04 mm[Formula: see text]/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.