| Objective: Percutaneous laser disc decompression(PLDD) wasintroduced by Choy as early as1984,and for the first time in1986, theapplication of Nd: YAG laser was used for the treatment of lumbar discdisease and success. Since then, PLDD had been generalized rapidly all overthe world. PLDD was approved by the U.S. Food and Drug Administration in1991; PLDD with Nd: YAG laser was also succeed by Qi qiang in1994inChina. There had been a lot of basic research and clinical case reports atpresent.PLDD,which is laser used in the medical field,is a more mature,effectiveand minimally invasive method to treating cervical or lumbar disc disease. Themain application of PLDD is the decompression and thermal effects oflaser.The basic principle is percutaneous needle through the nucleus pulposusunder the X-ray or CT fluoroscopy-guided, importing the optical fiberconveying the laser, vaporizing a certain amount of nucleus pulposus to reduceintradiscal pressure thereby reducing the protrusion compression on the nerveroot or spinal cord, in order to to relieve symptoms.In addition, DachengToshio think that PLDD also has anti-inflammatory analgesic In addition tothe decompression effects. Body reaction layer by the laser irradiatingtissue,and the outermost layer is below40℃, which is photobio the-activative-reaction (PAR).The main role is the thermal effect,which thedilation of blood vessels, reduction of pain substances, the normalization ofthe autonomic nervous system function and the improvement immune functionare combined to achieve the purpose of anti-inflammatory analgesic. TheIwatsuki etc. think that laser irradiation resulted in the degeneration of thenucleus pulposus proteins, thereby reduced the chemical inflammatory factor as the PLDD onset mechanism.As for PLDD,bio-thermal effects play a crucial role in the treatment, andtemperature change and its impact on the surrounding tissue has been thefocus of attention of clinicians. At present, most domestic and foreign reportsabout PLDD are basic research,and more confined to the surroundingtemperature change of laser disc,and internal temperature change still lack. Inthis study, goat intervertebral disc tissue were irradiated with the applicationof Nd: YAG laser (1064nm) under different parameters, observing thetemperature changes of the intervertebral disc between ablation process, andthus is more reasonable, safe and effective for PLDD to provide researchevidence in clinical.Method:144fresh lumbosacral segment of goat spines were usedwithout refrigeration,and the size is similar.Discs of the same level(L6/7) weremade into spine function unit (SFU),which contains the chosed disc and twosemi-vertebral bodies and removed muscles, ligament and vertebral arch,transverse process, spinous process, articular process, total144. The SFUswere divided into A and B groups on random,72specimens in each group. Inthe group A,the laser was emitted intermittently and in the group B the laserwas emitted continuous. The two groups were divided into3subgroupsrespectively,24specimens in each subgroup. The3subgroups correspond tothe total energies of250J,500J,750J respectively. Each subgroup is dividedinto3sub-subgroups respectively,8specimens in each sub-subgroup, and The3sub-subgroups correspond to the frequency of10Hz,20Hz,30Hzrespectively. The power was10W all.Specimens were punctured in the C-arm fluoroscopy. Takeing the disclateral middle as the puncture site, the needle parallel to the edge of up anddown of the disc. Under fluoroscopy inanteroposterior and lateral,the tip arelocated in the middle of int ervertebral disc. Parallel to and along theneedle,seting to a temperature measuring point every0.5cm from the disccenter to the outside,total3points, the medial, intermediate, and lateralmeasurementstemperature point respectively.Taking2mm Kirschner wire to drill the temperature channel from the disc rear perpendicular to needle andparallel to the disc upper and lower,and punch to reach the point.3DMMtemperature probe were placed in the three points,and the probes in extensionline of the needle. Pull out the needle core and placed in the optical fiber.Specimens were irradiated by1064nm Nd: YAG laser in accordance with thepre-launch mode and different parameters respectively. The laser is dividedinto the continuous emission and intermittent emission and the combination ofdifferent parameters,include energy and frequency.The energy is divided into250J,500J,750J; and frequency into10Hz,20Hz,30Hz. Eight specimens ineach group after randomization, Observing temperature changes in3pointsduring irradiation and calculating the temperature change.The experimentalspecimens wre stored at-20℃postoperative Immediately. After24hours,specimens were completely frozen and cut disc as biopsy.Result:1Temperature difference of the three measurement points in disc internal arelarger with the increase of the total laser energy during laser vaporization,andno significant change with the increase of the laser frequency.2At the same point and same total energy, the temperature difference in thecontinuous group is larger than in the intermittent group during laservaporization.The temperature difference in inside point compared, P>0.05,the difference was not statistically; the temperature difference in i middle andoutside points, P <0.05, the difference was statistically significant.3At the same point and different total energy, comparison between groups:between the750J group and500J,250J group in laser emitted intermittently, P<0.05, the difference was statistically significant. Between the750J group and500J,250J group in internal point in laser emitted continuous, P <0.05, thedifference was statistically significant; between750J group and250J group inintermediate and lateral points,P<0.05,the difference was statisticallysignificant.4At the same point and different frequency, comparison between groups:between the20Hz group and the30Hz group in the internal point in laser emitted intermittently, P <0.05, the difference was statistically significant,Different frequency groups in intermediate and lateral points, P>0.05, thedifference was not statistically significant.Between the20Hz group and30Hz,10Hz group in intermediate point in laser emitted continuous, P <0.05, thedifference was statistically significant, different frequency groups in internaland lateral points, P>0.05, the difference was not statistically significant.5At the same total energy and different point, the temperature difference islargein inside point, and it is small in lateral point. The temperature differencereduce gradually from inside to outside.6Histological and morphological studies: gross specimens show thevaporization chamber or carbonized traces in internal disc, and blackcarbonized material is visible in the cavity wall.Microscope (HE staining): the central disc was no organization and cell cavity,and the cavity edge scattered in a small amount of carbonized particles. Theannulus andcartilage endplate was no obvious damage. Histological changesare no significant difference between the laser intermittently group and thecontinuous group.Conclusion: When nucleus pulposus are ablated with1064nm Nd: YAGlaser, Temperature difference in laser continuous group is higher than theintermittent group,and laser intermittent is more secure. Disc internaltemperature is mainly affected by laser energy,the impact of the laserfrequency is small.The higher the total energy,the larger temperaturedifference. the thermal damage did not occur when the total energy is750J,PLDD has a higher security. |
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