Laser rapid drilling of bone tissue in minimizing thermal injury and debris towards orthopedic surgery

Traditional mechanical bone drilling is prone to heat generation and debris accumulation which will cause tissue damage in orthopedic surgeries. Therefore, research on contactless laser bone drilling has become a mainstream trend in the development of bone surgery. This study presents a laser rapid drilling strategy for bone surgery with minimizing thermal osteonecrosis and debris based on the design of dynamic focusing and spreading droplet cooling. The laser drilled hole suffered from low temperature (Tmax = 46.2 ○C) under clinically accepted threshold of 47 ○C, presenting osteocyte-filled lacunas, visible Haversian canals and increased pullout strength when compared with that following mechanically drilling. An intact bone column without debris was extracted from a 4-mm-deep hole in vitro on a sheep tibia which provides a clean surgical method with increased drilling rate of 0.94 mm3/s. The criteria dimensionless We constant related to spreading droplets leading to effective heat transfer is determined as2.8 × 103 × Re-1/2 ≤ We ≤ 1.9 × 10-2 × Re7, yielding a high convective coefficient of 0.11 W/mm2·K for cooling. The comprehensive results of laser bone drilling proved the effectiveness of the presented technology and setup, which is significant in realizing rapid, debris-free orthopedic surgery.