Ultrashort Laser Ablation of Cortical Bone: Literature Review and Experimental Evaluation

Abstract

<p>Mechanical instruments, such as saw and bur are commonly used for bone cutting during orthopedics surgeries. These conventional instruments showed good bone removal efficiency. Nonetheless, there are some issues with the use of the mechanical tools, such as ill-placed screws and elevation of tissue temperature, which results in thermal damage to the surrounding tissues. These difficulties accompanied with using mechanical tools led to laser ablation investigations. Lasers, including continues wave (CW) and pulsed, were considered to be a promising tool for bone ablation. When compared to mechanical tools, lasers produce less thermal damage to the surrounding tissues due to their ability to focus on a very small spot, which also produces more precise ablation. Lasers also produce no significant mechanical vibrations within the surrounding tissue and thus less mechanical damage and cracks occur during ablation. Performances of laser ablations are measured by several factors; such as collateral damage, machining time, ablated depth, and ablative precision. In this thesis work, a literature review was conducted with the aim of understanding the bone characteristics that are related to the optical properties of bone, which leads to a better understanding for ablation mechanisms. This helps in a proper choice of laser parameters for a certain tissue ablation, and thus avoiding collateral damage.</p> <p>Some laser parameters (pulse energy, scanning speed, and number of passes) were characterized as a first step towards producing large holes. The effect of each one of these laser parameters on the groove depth was found. The feasibility of the ultrafast laser in creating large scale holes was examined, using two scanning strategies: (i) concentric circles scanning, the largest crater depth measured using this procedure was 3.81 mm, (ii) helical scanning, which was used to reduce the machining time, using this procedure a micropillar was created with 12 passes in just 2.5 minutes.</p>