| Objective: Percutaneous laser disc decompression(PLDD) was firstly introduced by Choy in 1987, Choy and Ascher reported the experiment outcome and the clinical application in 1987. Since then, PLDD has been generalized all over the world, lots of basic study and clinical cases have been reported one after another. PLDD is the product of laser technique and medical science, it's a effective, micro-invasive skill to cervical spondylosis and lumbar spondylosis. The rudiment of PLDD is to vaporize the nucleus pulposus using the laser which is inserted into disc under X-ray or CT, then decrease the pressure of disc to make the herniated disc recovery, decrease the pressure on nerve root to improve the symptom. There always has a focus about which kind of laser to use in PLDD and how about the safety. At present, the 1064nm Nd:YAG laser and the 980nm diode laser are used widely in PLDD, they both have the close wavelength, but the comparison of bio-heating effectiveness to nucleus pulposus between them have seldom been seen. The fresh goat intervertebral lumbar discs were radiated by Nd:YAG laser and 980nm diode laser in this study, the ablated quality of nucleus pulposus and the morphous of the cavity after radiating and the changes of temperature around discs during radiating were observed to compare the ablation ability to nucleus pulposus and the safety between two lasers.Method: 80 whole fresh uniced goat spine were used, discs of the same level (L6/7 was chosed in this study) were made into spine function unit (SFU) which contains the chosed disc and two semi-vertebral body. The redundant muscle and ligament was removed, just remained an intervertebral foramen in the back of SFU. The SFU was nyxised under perspective after weighed on electronic balance. The anteroexternal site of the disc was chosed to nyxised. The transfixion pin should parallel the disc. The needle tip was in the middle of the disc in the anteroposterior radiography, and in the pone close to middle of the disc in the lateral radiography. Pull out the needle core, insert the optical fiber with single sweep tee into transfixion pin. The probes of three digital avometer were embedded at the anterior border (AB), posterior border (PB) of discs and at the intervertebral foramen (IF) respectively. The SFU were radiated by Nd:YAG laser and 980nm diode laser, and they were divided into five groups according to the final energy from 200J to 1000J, each group had 8 discs. Then weigh the SFU again after radiating. The ablated quality of nucleus pulposus after radiating and the changes of temperature at three important sites around discs during radiating were observed. After procedure, slit the disc horizontally and observe the morphous of the cavity. Then measure the long and wide axis of cavity by sliding caliper.Result: 1 The ablated quality of SFU was greater at higher radiating energy in both lasers. When compare the ablated quality among different energy groups in Nd:YAG laser, there is statistical significance between 200J group and group in which the energy is greater than or equal to 600J, 400J group and group in which the energy is greater than or equal to 800J, 600J or 800J group and 1000J group; When compare the ablated quality among different energy groups in 980nm diode laser, there is statistical significance between 200J group and group in which the energy is greater than or equal to 600J, 400J group and group in which the energy is greater than or equal to 600J, 600J group and 800J or 1000J group.2 At the same energy, the ablated quality of SFU was greater in 980nm diode laser than in 1064nm Nd:YAG laser. There is statistical significance when at 200J, 400J group (P<0.05) and at 600J, 800J, 1000J group (P<0.01).3 The changes of temperature at the AB, PB of discs and at the IF were greater at higher energy during radiating. When compare the temperature changes at the AB during radiating among different energies in Nd:YAG laser, there is statistical significance between 200J group and group in which the energy is greater than or equal to 600J, 400J group and group in which the energy is greater than or equal to 600J, 600J group and 1000J group. At the PB or at the IF, there is statistical significance among all energy groups; When compare the temperature changes at the AB during radiating among different energies in 980nm diode laser, there is statistical significance between 200J group and group in which the energy is greater than or equal to 600J, 400J group and group in which the energy is greater than or equal to 600J, 600J or 800J group and 1000J group. At the PB or at the IF, there is statistical significance among all energy groups.4 The changes of temperature at the same site during radiating were higher in 980nm diode laser when using the same energy (P<0.01).5 The changes of temperature at the PB of disc were higher than two others in both lasers under the same energy (P<0.05).6 The cavities made by Nd:YAG laser are toroid or ovale under naked eye observation, while the cavities made by 980nm diode laser are elliptic. There is statistical significance when compare the long axis between two lasers at the same energy(P<0.01). When compare the wide axis, there is statistical significance at the 200J (P<0. 05) group and at the 400J (P<0.01) group, there is no statistical significance at the 600J, 800J, 1000J energy group.Conclusion: 980nm diode laser has better ablation ability to nucleus pulposus than 1064nm Nd:YAG laser, but the latter is more safe.
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