Effects Of Pulsed Radiofrequency With Different Exposure Time On Pain Threshold And Nerve Structure In The Rat CCI Model

Objective:The effects of pulsed radiofrequency on pain threshold and microstructure of sciatic nerve in rats with chronic sciatic nerve constriction injury were observed and compared in different time of stimulation.Methods:We studied 72 male SD rats weighing about 210-230 g in this randomized trial and randomly divided the rats into: shame PRF group,PRF-120 s group,PRF-480 s group,PRF-720 s group,and each group 18.After the establishment of CCI in rats,the shame PRF group only placed the pulse radiofrequency needle on the sciatic nerve instead of any PRF.The other 3 groups were given PRF intervention for 120 s,480s and 720 s respectively(voltage 55 V,frequency 2Hz).The mechanical withdrawal threshold(MWT)and thermal withdrawal latency(TWL)were respectively measured before the model,model establishment time and at 1,4,7,10,14,17,21 days after PRF.Examination of the changes in the microstructure of the sciatic nerve in the PRF treatment of all rats by electron microscopy after stimulated in 21 d.Results:Before and after the model establishment that there was no significant difference in the MWT and TWL of among groups(P >0.05);After CCI model successfullyestablished(7 d after the model),TWL and MWT of all groups were significantly lower than those before establishment of the model(P <0.05);Compared with the shame PRF group,the TWL and MWT of the other 3 groups were significantly increased at 4,7,10,14,17 and 21 days after PRF(P <0.01);MWT and TWL of PRF-120 s group were significantly lower than those in PRF-480 s group and PRF-720 s group at 21 d after PRF(P <0.05);Compared with PRF-480 s group,PRF-720 s group had higher TWL and MWT at 21 d after PRF than PRF-480 s group(P <0.05).The sciatic nerve of each group under the electron microscope showed no significant degeneration of the myelin axon and the axon of each PRF group showed a small amount of phospholipid abscission.In PRF-120 S group and PRF-480 S group,a small part of irregular shape myelin sheath appeared.The lamellar structure was swollen and loose,and there was myelin sphere formation.In PRF-720 S group,the lamellar structure was swelling and loose,which was higher than that in PRF-120 S and PRF-480 S group.Conclusion:1.PRF treatment can significantly alleviate mechanical and thermal allodynia of the rat's CCI model,and produce a definite pain treatment effect on NP.2.Within 120 s to 720 s,prolonging the time of PRF treatment can improve the analgesic effect of PRF on CCI rats.3.No serious irreversible damage to the sciatic nerve was caused by the exposure time established in this experiment,but the prolongation of PRF duration may lead to more severe medullated nerve fiber edema.