Experimental Evaluation of Percutaneous Lumbar Laser Disc Decompression Using a 1414 nm Nd:YAG Laser

Abstract

BACKGROUND: Laser ablation under an epiduroscopic view allows for the vaporization of a small amount of the nucleus pulposus, causing a reduction in intradiscal pressure and relief of radicular pain. Currently, Ho:YAG and Nd:YAG lasers are commonly used for spinal diseases. However, the use of the Nd:YAG laser for intra-spinal procedures can be limited because of thermal injury and low efficacy.

OBJECTIVE: To investigate the efficacy and safety of epiduroscopic laser ablation using a 1414 nm Nd:YAG laser, we examined that laser ablation was able to penetrate nucleus pulposus without heating surrounding tissues and without mechanical damage to surrounding tissue.

STUDY DESIGN: Our experiment involved live and cadaveric animal studies and a human cadaveric study.

SETTING: University in Korea.

METHODS: Two live pigs, 3 porcine cadavers, and 2 human cadavers were used. For the in vitro study, intradiscal and epidural pressure and temperature were compared in vertebral columns obtained from 3 porcine cadavers before and after laser ablation. For the in vivo study, 2 pigs were used to simulate percutaneous epiduroscopic laser ablation. They were observed for behavioral changes and neurological deficits for one month after the laser ablation procedure. Two human cadavers were used for placing the laser fiber and epiduroscope in the correct target site through the sacral hiatus. Histological analysis was also performed to observe any damage around the ablated lesion.

RESULTS: Both intradiscal and epidural pressure were markedly reduced immediately after laser ablation as compared with the pre-ablative state. The amount of the pressure decrease in the intradiscal space was significantly greater than that in the epidural space (45.8 ± 15.0 psi vs. 30.0 ± 9.6 psi, P = 0.000). The temperature beneath the ipsilateral spinal nerve, which was the nearest site to the laser probe, never exceeded 40° C. Histology revealed no evidence of thermal damage to surrounding structures, including the spinal nerves, end plates, and vertebrae, after laser ablation. All live pigs showed normal behavior without any sign of pain. In the human cadaveric study, there was no case of targeting failure or dural laceration. The mean time to reach the target region was less than 5 minutes.

LIMITATIONS: The pressure measurements were performed on cadavers and not in vivo. Cadaver models cannot account for intradiscal pressure changes that occur during live muscle contraction and different positions, which may affect results. Moreover, although we controlled temperatures with heat baths, vascular and cerebrospinal fluid circulations were not simulated. Those circulations may change the temperature results in vivo.

CONCLUSIONS : The 1414 nm Nd:YAG laser can be used effectively and safely under the guidance of a spinal epiduroscope in an in vivo porcine model and in a human cadaveric model. STUDY APPROVAL: Approval for the current study was granted by the Institutional Review Board of our institute (approval number: 1-2014-0049).