Comparison Of The Ablation Ability Of The Nd:YAG Laser(1064nm) To Nucleus Pulposus Between Different Parameters

Objective: PLDD (percutaneous laser disc decompression) is a more mature, safe, reliable, and minimally invasive method to treatment of cervical or lumbar disease. PLDD is widely used in the treatment of cervical or lumbar disease and has achieved good clinical efficacy.PLDD mainly takes advantage of the photothermy between the laser and the disc nucleus pulposus tissue. Currently, there are a large number of reports of basic research of PLDD, including the intervertebral disc pressure, evaporation, temperature, spinal stability and so on. But, for laser ablation of nucleus pulposus capacity, the studies were under the single parameter more. Studies and frequencies of laser ablation of nucleus pulposus capacity in different energies is still lack. In this study, the goats lumbar disc tissue were irradiated by different energies and frequencies of Nd:YAG laser (1064nm), observation of the poor quality of specimens before and after irradiation and vaporization cavity size after irradiation, to compare the laser ablation ability in different parameters on the f nucleus pulposus. to provide research based on more rational, safe and effective laser parameters for clinical PLDD.Method: 144 whole fresh uniced goat spines were used, discs of the same level were made into spine function unit (SFU) which contains the chose disc and two semi-vertebral bodies. The redundant muscle, ligament and vertebral arch, transverse process, spinous process, articular process was removed. The SFUs were divided into A and B groups on random, 72 specimens in each group. The laser was emitted intermittent in the group A, and emitted continuous in the group B. The two groups were divided into 3 subgroups respectively, 24 specimens in each subgroup. The subgroups correspond respectively to the total energies of 250J, 500J, 750J. Each subgroup is divided into 3 sub-subgroups respectively, 8 specimens in each sub-subgroup, and The 3 sub-subgroups Correspond respectively to the frequency of 10Hz, 20Hz, 30Hz. The power in every group was 10W.1 The SFUs were transfixed in the C-arm radiography after grouped and weighed on electronic balance. The transfixion pin should be parallel to the up and down disc edge. Two SFUs were weighed on electronic balance before laser irradiation, and the two SFUs were weighed on electronic balance again after one SFU was irradiated. The difference of the change in the quality between the two SFUs is the amount of vaporization.2 After procedure, all SFUs were Stored at -20℃in the refrigerator until completely frozen for 24 hours. Sliting the disc horizontally and observe the morphous of the cavity. Then measure the long and wide axis of cavity by sliding caliper.Result: 1 Compared the ablated ability to nucleus pulposus between the different parameters of the same group:Group A (The laser was emitted intermittent): At the same energy, the ablated quality of SFU is no statistical significance when the frequency is 10Hz and 30Hz (P>0.05), but when the frequency is 20Hz, the ablated quality exceed 10Hz and 30Hz (P<0.05); At the same frequency, the ablated quality of SFU was no statistical significance when the energy were 250J and 500J (P>0.05), but when the energy is 750J, the ablated quality exceed 250J and 500J (P<0.05). There is no interaction between frequency and energy. When the frequency is 30Hz and the energy is 750J, the ablated quality is maximum.Group B (The laser was emitted continuous): At the same energy, the ablated quality of SFU is no statistical significance at all groups (P>0.05); At the same frequency, the ablated quality of SFU was no statistical significance when the energy were 250J and 500J (P>0.05), but when the energy is 750J, the ablated quality exceed 250J and 500J (P<0.05). There is no interaction between frequency and energy (P>0.05). When the energy is 750J, the ablated quality is maximum.2 Compared the ablated ability to nucleus pulposus between the same parameter of the different groups:The ablated quality of SFU was greater in the group B (the laser was emitted continuous) than group A (the laser was emitted intermittent) when the parameters was 750J/30Hz (P<0.05), and the remaining groups were not statistically significant.3 Compared the long and wide axis of the cavities between the different parameters of the same group:Group A (The laser was emitted intermittent): At the same energy, the long and wide axis of the cavity are no statistical significance when the frequency is 10Hz and 30Hz (P>0.05), but when the frequency is 20Hz, the long and wide axis of the cavity exceed 10Hz and 30Hz (P<0.05); At the same frequency, the long and wide axis of the cavity were no statistical significance when the energy were 250J and 500J (P>0.05), but when the energy is 750J, the long and wide axis of the cavity exceed 250J and 500J (P<0.05). There is no interaction between frequency and energy (P>0.05). When the frequency is 20Hz and the energy is 750J, the long and wide axis of the cavity is all maximum.Group B (The laser was emitted continuous): the long axis of the cavity: the size of the long axis of the cavity in every group is inconsistent (P>0.05), When the energy is 750J and the frequency is 10Hz, the long axis of the cavity is maximum.The wide axis of the cavity : At the same energy, the wide axis of the cavity is no statistical significance (P>0.05) as the frequency is changed; At the same frequency, the wide axis of the cavity no statistical significance when the energies were 250J and 500J (P>0.05). when the energy is 750J, the wide axis of the cavity exceed 250J and 500J (P<0.05). There is no interaction between frequency and energy (P>0.05). When the energy is 750J, the wide axis of the cavity is maximum.4 Compared the long and wide axis of the cavity between the same parameter of the different groups:The long axis of the cavity was greater in the group B (the laser was emitted continuous) than group A (the laser was emitted intermittent) when the parameters were 750J/20Hz and 750J/30Hz (P<0.05), and the remaining groups were no statistical significant.The wide axis of the cavity was greater in the group B (the laser was emitted continuous) than group A (the laser was emitted intermittent) except the parameters were 500J/10Hz and 500J/30Hz (P>0.05) which was no statistical significant.Conclusion: At the same parameter, both the quality of vaporization and the form of cavity are influenced by the mode of the laser. The ablation ability is influenced by the different modes of the Nd:YAG laser when the parameter is changed—at the same energy, the ablation ability is influenced by the frequency of the laser; at the same frequency, the ablation ability accreted with the increase of energy of laser.