Exploration Of Analgesic Mechanism Of Precise Needling At Myofascial Trigger Points Based On Motor Endplate Dysfunction

Objective:Myofascial trigger points(MTrPs)are the main causes of chronic soft tissue pain.The main manifestations of MTrPs are local pain and referred pain with the symptoms of autonomic and skeletal muscle dysfunction.We successfully created the model of MTrPs by blunt stroke plus eccentric exercise.Histomorphometric and electrophysiological observations revealed collapsed nodules of MTrPs and spontaneous electrical activity(SEA).A large number of researchers have speculated that contractile nodules occur in the motor end-plate and excessive release of acetylcholine(ACh)is the cause of SEA and collapsed nodules.However,relevant studies have not yet given the pathological histological evidence of the occurrence of MTrPs in motor endplates.At the same time,a large number of MTrPs clinical studies and systematic reviews show that needling at MTrPs can effectively improve somatic pain and dysfunction.If MTrPs is caused by dysfunction of motor endplates,whether precise needling at MTrPs can decrease ACh and SEA is unclear.It is hypothesized that needling at MTrPs can reduce SEA,whether there is a correlation between SEA and pain reduction,and if SEA can be used to guide MTrPs needling treatment and fully inactivated still need a further research.Through carry out the above research,we can further understand the peripheral mechanism of dry needling treatment of MTrPs.The treatment corresponding to precise needling at MTrPs is the remote needling at the distal of MTrPs.Some researchers have suggested that remote needling at MTrPs has a certain effect on MTrPs pain.The remote needling mechanism is mainly through the endogenous descending control pathways,such as the secretion of enkephalin and β-endorphin,and the conditional pain modulation(CPM).Studies have confirmed that remote needling play a role in the expression of certain proteins in the endogenous opioid system.However,no research has been found on the role of CPM in remote needling analgesia.Needling can lead to mechanical damage to muscle tissue,stimulate Aδ and C-type fibers,and activate spinal nerves such as nucleus raphe magnus to negative feedback modulation mechanism,causing analgesia.This mechanism of negative feedback modulation is also known as diffuse noxious inhibitory control(DNIC).In human studies,DNIC is often expressed as CPM.It is indicated that persistent pain in one part of the body(conditional stimulation)can inhibit the pain sensation caused by noxious stimulation(experimental stimulation)in another part of the body is known as "pain inhibits pain".Through the study of CPM,we can understand whether the non-precise needling at MTrPs can play an important role in the regulation of pain.In this study,motor end-plates were visualized by acetylcholinesterase(ACh E)staining.MTrPs contraction nodules were confirmed to occur in the motor endplates.The ACh and electromyogram were used to observe motor end-functions.Then,observe whether dry needling treatment can reduce SEA.To compare the electromyographic and biochemical changes of precise needling at MTrPs and needling at non-MTrPs,and analyze the differences between the two treatment methods.Then through clinical studies,compared MTrPs dry needling group,electromyography guided MTrPs dry needling group and electromyography guided MTrPs wet needling group,analysis of the pain changes.Finally,the role of remote needling in the treatment of endogenous pain was assessed by the CPM.It provides the most advanced theoretical basis and scientific guidance for the occurrence,diagnosis and treatment of MTrPs.Methods: 1st PartA total of 32 male SD rats were randomly divided into four groups: Two control groups(C1 and C2),tow model groups(M1 and M2).C1 and M1 used for acetylcholinesterase(ACh E)staining while C2 and M2 used for measure the contents of acetylcholine(ACh)in samples.The model groups were formed by a blunt striking injury and eccentric exercise applied to the left gastrocnemius of rats for 8 weeks.After one month,the spontaneous electric activity(SEA),ACh E optical density(OD),width of MTr S muscle fibers and the level of ACh was performed.2nd PartForty-eight male Sprague–Dawley rats were divided into four groups.Thirty-six rats were assigned to three model groups,which underwent the MTrPs modeling intervention.Twelve rats were allocated to the blank control(BC)group.The rat model groups were constructed via blunt striking injury and eccentric exercise that were applied to the left gastrocnemius muscle(GM)for 8 weeks and with a recovery period of 4 weeks.After modeling,the 36 rats were randomly subdivided into three groups: MTrPs model control(MC)group,a dry needling group for puncturing at MTrPs(DNM),and a dry needling group for puncturing at non-MTrPs(DN-n M).After anesthesia in rats,MTrPs were determined by electromyography,then left side of spinal cord of L4-l6 and GM muscles were obtained.The effects of the treatments were analyzed by EMG changes,and ACh,n ACh R,and ACh E concentrations were measured by Elisa,The expression of NGF、Trk A in GM and the expression of BDNF、Trk B in spinal cord were tested by western blot.3rd PartRecruit 45 patients with neck and shoulder pain according to the inclusion and exclusion criteria from the Shanghai Sport Injury Orthopaedics Hospital of Shanghai University of Sport and Shanghai Hudong Hospital Pain Department.All participants participated in the trial to demonstrate the purpose,protocol,and procedures of the trial.Informed consent forms were signed.Participants were randomly divided into three groups: myofascial trigger point dry needling group(DN)and dry needling with EMG guided group(DN-EMG),wet needlling with EMG guided group(WN-EMG).EMG and VAS were analyzed 4th PartA total of 23 males and 22 females participated in a control and CPM session in a randomized,crossover fashion.In the control session,pressure pain thresholds(PPTs)were assessed by using handheld algometry at infraspinatus,brachioradialis,and gastrocnemius muscles on the dominant side.A painful pressure at m.infraspinatus equivalent to 7 cm on VAS(PVAS7)was applied and kept constant for 60 s.Upon release,participants indicated the area of the pressure-induced pain on a digital body chart.The CPM pain session was identical to the control session but here,tonic pain was induced in the contralateral lower leg using cuff algometry.Analysis was performed separately for each gender.Results: 1st Part 1.1 There are a large number of SEA(positive neurons,fibrillation potentials,and beam-fibrillation potential neuronal or myogenic lesions)at MTrPs in M1 and M2 groups.Quantitative EMG results showed that the SEA of low amplitudes and frequency of high amplitude of M1 were significantly higher than C1.1.2 The ACh content in MTrPs in M1 group was significantly higher than that in C1 group(p<0.01).The ACh E OD value of M2 group was significantly lower than that of C2 group(p < 0.01).In addition,muscle fiber in the ACh E-stained area in the M2 group were greater than in the C2 group(p < 0.05).2nd Part 2.1 Compared with the blank control group,SEA in the model group had higher amplitude and frequency.After treatment in the DN-M group,amplitude and frequency of low-amplitude and high-amplitude amplitudes of SEA were significantly reduced(p<0.01).In addition,after the treatment in DN-n M group,the amplitude of low amplitude amplitude of SEA decreased.Between groups,the amplitude and frequency of DN-M group were significantly decreased after dry needlingcompared with other groups(p<0.01).2.2 After dry needling,ACh levels in DN-M group were significantly lower than MC group(P<0.05).The ACh R levels in the MC and DN-n M groups were significantly higher than those in the DN-M group(p<0.05).The concentration of ACh E in DNM group was significantly higher than the other groups(p<0.01).2.3 The NGF,Trk A,BDNF,Trk B were high in model groups,but did not see any changes after dry needling.3rd Part 3.1 Although the WN-EMG group can rapidly reduce the self-generating activity of the electromyogram through drugs,the self-generating activity in the later stage will reappear,and the patient’s pain condition has not been improved.3.2 DN and DN-EMG groups effectively reduced SEA activitiesd,pain and referred pain area(p<0.01).4th Part 4.1 PPT values of the three muscles increased after CPM in both sexes(P<0.05).4.2 The PVAS7 of women was lower than that of males on both days(P<0.05),whereas the size of the pain area was significantly larger(P<0.05)on both days.4.3 No correlation was found between the changes in pain area and the magnitude of CPM response in either group.Conclusion: 1.MTrPs found enlarged and thick muscle fiber structure at the end plate position, which was consistent with the morphology of MTrPs,confirming that MTrPs occurred in the motor endplate.Increased ACh concentration and decreased ACh E expression at the endplate are the cause of abnormal SEA and local contracture.2.Dry needling precise at MTrPs is more effective than non-MTrPs dry needling in reducing amplitude and frequency of SEA and biochemical abnormalities at the trigger point endplate.3.Electromyography can be used as an observation tool for MTrPs position finding and MTrPs inactivation status.Electromyogram guided trigger point dry needling,triggering local twitch response,which can fully inactivate MTrPs and reduce pain levels.4.There are sex-specific differences in referred pain that do not correlate with a CPM response.