| Objective: Percutaneous laser disc decompression (PLDD) has become one of the most safe and effective therapies for the disc herniation since the first successfully report by Choy in 1987, which has been extensively used for clinical treatment of the cervical and lumbar disc herniation and the outcomes were satisfying. However, the dose of the laser for PLDD was defferent greatly, and there was potential damage for the surrounding tissues as the laser energy adding. Some cases of untoward reaction such as pain and numbness for the reason of overdose irradiation of laser were reported. So, one question comes, which is how to achieve goals of therapy successfully and reduce the total irradiation of the laser and elevate the safety of the procedure. Literature reviewing , we found that Sato of the Japan had reported that ICG-dye could enhance the capability of 810nm diode laser vaporizing the nucleus pulposus. Since the 980nm diode laser has powerfully photo-thermal effect on the biological tissues, which has been used widely. We plan to stain the nucleus pulposus using ICG and then observe the effect of 980nm diode laser on vaporizing the NP tissue, with the goal of ablating the NP safely and effectively using less laser energy. Methods: Fresh goat lumbar specimens were obtained and 144 spinal function unit (SFU) were made, pedicle of vertebral arch, transverse process, spinous process and articular process removed, 24 of which were selectively on random for the experiment of determinating the concentration of the dye. And then divided into 3 groups on random, 8 specimens in each group. 120 SFU were divided into blank-group, water-group and the ICG-group on random. And then every group was divided into 5 groups by means of the laser energy, used for analysis of capability of laser ablation. The temperatures of three spots an anterior and posterior border of the disc and medial wall of intervertebral foramen were measured during the procedure of PLDD in the groups of total laser irradiation of 490J. The areas of the vaporized carves were calculated postoperatively.1 Experiment for determination of the concentration of the ICGAs the outcomes of the preliminary experiment, total laser energy of 350J was set. And 100μl ICG was injected into the middle of the NP tissue, the concentration of which was 0.5mg/ml, 1.0 mg/ml and 2.0 mg/ml. then PLDD was done. The weights of the SFUs were measured preoperatively and postoperatively. The concentration of the group, whose weight reduced the most was selective for the posterior experiments.2 Experiment for analyzing the ablation of the NP tissue100μl distilled water and ICG C=1.0 mg/ml) as injected into the NP of the water-group and ICG-group respectively. Weight was measured and then PLDD was manipulated using 980nm diode laser. The total energy of laser was 70, 210, 350, 490 and 630J, the laser irradiation of set as T=105s,on=1.0s,off=0.5s. The weights of specimens were measured before and after PLDD, by which then the ablation ability of the laser was analyzed.3 Experiment for the safety of PLDDFor the groups given total laser energy of 490J, the temperatures of the anterior border(AB), posterior border(PB) of the disc and medial wall of intervertebral foramen(IF) were measured during the PLDD, and the highest temperature was obtained. The specimens were froze into a -20℃refrigerator for 24 hours. Then they were transversally cut off from the middle of the intervetebral space by a sharp blade. The length and wide of the vaporized cave was measured by vernier caliper and the area of which was calculated.Results: 1 The ablation of nucleus pulposus accreted with the addition of laser energy. The ablation of each group at the total energy of 70, 210, 350, 490, 630J respectively was show as follow. The blank group: 0.0754±0.0046g, 0.1170±0.0306 g, 0.1454±0.0410 g, 0.1560±0.0058 g and 0.1742±0.0429g,energy group comparison, P<0.01; The distilled water group: 0.0596±0.0110g, 0.0719±0.0228g, 0.1246±0.0293g, 0.1518±0.0079g and 0.2133±0.0513g, energy group comparison, P<0.01; The ICG-dying group: 0.0699±0.0098 g, 0.1067±0.0154 g, 0.1978±0.0569 g, 0.2224±0.0358 g and 0.2626±0.0241 g, energy group comparison, P<0.01.2 At the equal energy level, the ablation of the blank group was less than the other two groups at a lower energy(E<490J),however, the distilled water group was more than the blank group when the energy was higher than 630J, still less than the ICG-dying group.3 At the equal energy level, there was no difference between the ICG-dying group and the blank group when the energy was lower than 350J, however there was dramatic difference when the energy was higher than 350J , P<0.01.4 ICG-dying of nucleus pulposus can elevate the vaporize rate, of which the blank group was 0.4mg/J and the ICG-dying group was 0.5mg/J respectively.5 The vaporized areas of the blank-group, water-group and the ICG-group were 3.8877±1.7499mm2, 5.5676±2.5662 mm2 and 3.7909±1.6687 mm2, as the total laser energy was 490J, and there was no difference among them, P>0.05.6 As the total laser energy was 490J, the maximum add of the temperature was 8℃,and there was no difference between the bank-group and the water-group, P>0.05; however, they were higher than the ICG-group, P<0.01.Conclusion: The ablation of nucleus pulposus accreted with the increase of energy of diode laser. ICG-dying could elevate the vaporize rate, which enhanced the ability of 980nm diode laser ablating nucleus pulposus when the total laser irradiation energy was more than 350J. So, the objective of ablating nucleus pulposus selectively and safely at a lower power was achieved.
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