Acupuncture for chronic musculoskeletal pain: the effect of needle placement, pain adaptability and endogenous pain controls
Creators: name: Wong Lit Wan, Dawn
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 320999
subject: Neurosciences not elsewhere classified
classificationCode: 420803
subject: Traditional Chinese medicine and treatments

description: Chronic musculoskeletal pain (MSK) affects one in four people worldwide and negatively impacts on individuals’ physical, mental and financial health. With the ageing population the prevalence of MSK is expected to increase and so is the burden of MSK. Thus, it is important to provide effective and safe analgesic treatment. Acupuncture has been used clinically and is reported to be safe and cost-effective for the treatment of MSK. However, there is no validated and optimal acupuncture treatment protocol to guide clinical practice. Conflicting results about the efficacy of acupuncture for MSK were found. Some studies reported that acupuncture was more effective than sham acupuncture in treating MSK while others reported no difference between the two. It is thought that acupuncture responder and non-responder subgroups were not differentiated during the trial recruitment phase, and this could have diluted the results leading to the lack of difference between real and sham acupuncture. Participants’ characteristics such as pain history and expectancy to acupuncture were reported to be associated with acupuncture pain relief. It is unknown if other characteristics such as potency of endogenous inhibitory controls, which were reported to be related to acupuncture, could impact on acupuncture analgesia. This project aimed to investigate such hypothesis by conducting two systematic reviews and four experimental studies using psychophysical methods. The relationship between potency of pain adaptability, conditioned pain modulation (CPM) and local acupuncture was explored.<br><br>The first systematic review of this project assessed the effects of local points and distant points in the treatment of MSK. The meta-analysis (17 studies, n=693) found that needling local points reduced pain more than the distant points, and among the local points, stimulation of Ashi points (tender points) showed a better efficacy than the classical acupuncture points. These results contributed to the design of the acupuncture protocol for the Acupuncture Response Study.<br><br>The second systematic review (14 studies, n=1788) investigated the possibility of identifying psychophysical subgroups in individuals with knee osteoarthritis (OA). Qualitative analysis found that pressure pain threshold (PPT) and temporal summation of mechanical punctate pain were potential measures to subgroup knee OA participants.<br><br>The first experimental study, the Segmental Inhibition Study (n=21), investigated whether vibration could be used to induce segmental inhibition (SEG) and if SEG differed between the pain adaptive (PA) or pain non-adaptive (PNA) healthy participants. The findings showed that vibration did not induce analgesia. Thus, it could not be determined whether the PA and PNA had different potency of SEG. Since this protocol of vibration failed to induce SEG, it was not used in the Acupuncture Response Study, and thus there were no subgroups based on SEG in that study.<br><br>The second experimental study, the Pain Adaptability and Acupuncture Analgesia Study, investigated whether pain adaptability impacted on acupuncture analgesia in healthy participants. A cross-over design with real and sham acupuncture at the left arm was used. Acupuncture analgesia was measured using PPT at the right and left arms and at the right leg. The PA showed better analgesia from the sham acupuncture than real acupuncture whereas the PNA responded to both forms of acupuncture similarly. Further, irrespective of the mode of acupuncture used, the PA showed a better analgesic effect at the right arm and right leg, whereas the PNA showed a better analgesic effect at the left arm. This shows that PA and PNA responded differently to different modes of acupuncture.<br><br>The third experimental study, the Pain Adaptability and MSK Study, aimed to determine an appropriate protocol to identify PA and PNA among MSK participants (n=43), to further explore their characteristics (demographics, potency of endogenous pain controls and autonomic activity), and to compare their pain adaptability with healthy participants (n=23). Cold pressor tests (CPT) at 2°C and 7°C were used to determine their pain adaptability. PA and PNA were identified in the MSK participants at both temperatures. There was no difference in the distribution of PA and PNA, and no difference in completion rate between the two CPTs. It was thus concluded that both temperatures could be used to determine pain adaptability in MSK participants. No difference was found in demographics, potency of endogenous pain controls and autonomic activity between the PA and PNA MSK participants. The only significant difference found was that PA reached their maximum experimental pain faster than the PNA during the CPT, which is in line with previous pain adaptability studies in healthy participants. Trends were found that the PA had less pain in the 24 hours preceding the CPT and less comorbidities. No difference in pain adaptability was found between the MSK and healthy participants.<br><br>The final experimental study, the Acupuncture Response Study, examined whether the potency of CPM or pain adaptability impacted on the analgesic effect of local acupuncture in MSK participants (n=35). Overall, the MSK participants reported an improvement in their clinical pain and physical health after eight sessions of local acupuncture. Those with severer pain or poorer CPM at baseline showed better improvement in the intensity of their clinical pain. PA individuals had shortened pain duration (hours in pain), but did not differ in pain reduction compared with PNA after acupuncture. Local acupuncture improved pain modulation as those with poorer CPM at baseline showed an improvement in their potency of CPM after acupuncture; and PNA individuals became more pain adaptive. In summary, individuals’ potency of CPM and the status of pain adaptability influenced response to local acupuncture and in different manners.<br><br>This exploratory project had a small size and the Acupuncture Response Study did not have a control group. Further larger studies with proper controls are necessary to confirm that local acupuncture analgesia is dependent on the status of CPM and pain adaptability and on the mode of needling so as to guide practice and predict clinical outcomes. Local acupuncture has great potential for clinical use for its safe and easy application. Distant needling and the combined local and distant needling should also be studied in relevance to individual differences in pain modulation.