Thermal Effects in the Ablation of Bovine Cortical Bone with Pulsed Laser Sources

Abstract

Lasers have advantages as bone surgical tools over mechanical methods, but two goals should be achieved to assure its use: Similar ablation rates to those obtained with mechanical tools (1 mm3/s at least) and to avoid thermal damage, a condition that can prevent proper bone healing. We present results of cow femoral bone with a 355 nm nanosecond (ns) and a 1064 nm picosecond (ps) pulsed laser sources that allow us to discuss the influence on the process of pulse duration and the selective ablation through high energy absorption (as bone highly absorbs 355 nm radiation). The treated samples were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. The evaluation of the thermal effects produced in the samples shows clear differences between both laser sources: On one hand, the ns laser allows reaching high ablation rates (around 1 mm3/s); Raman spectra show no signal of bone carbonization, but unavoidable thermal effects in the form of melted and solidified material have been observed by electron microscopy in the samples treated with this laser. On the other hand, ablation without any sign of thermal effects is obtained using the ps laser, but with lower ablation rates, (around 0.15 mm3/s).