Effect of 980-nm diode laser and 1064-nm Nd:YAG laser on the intervertebral disc--in vitro and in vivo studies.

Objective: Our aim was to histologically evaluate the thermal changes in bovine intervertebral discs caused by 980-nm diode and 1064-nm Nd:YAG lasers. Further aims were to standardize the technique for in vivo animal research and to study its efficacy for clinical practice.
Background: When conservative methods fail, surgery has so far been the only measure for severe back pain due to disc prolapse and herniation. Recently, the minimally invasive technique of laser disc decompression has become more popular because it has advantages over open surgery in properly selected cases.
Methods: In vitro studies were done with Nd:YAG and diode lasers (1064 and 980 nm, respectively) on bovine intervertebral discs using a bare fiber tip or a focusing lens attached to a fiber tip. These studies were followed by in vivo studies in a canine model using a Nd:YAG laser with a bare fiber tip. Autopsies were done immediately and at 3, 6, 9, and 12 mo after ablation and the histopathology of excised discs was evaluated.
Results: Depending upon the depth of ablation and the intensity of charring and carbonization, a standardized energy density and pulse duration were identified.
Conclusion: Nd:YAG laser with initial delivery of 40-W laser power and a reduced power of 10-15 W thereafter, delivering a total energy density of 1500-2000 J/cm(2) using a bare fiber tip, is recommended for clinical applications.