Conditioned pain modulation and analgesia of local acupuncture for chronic musculoskeletal pain: An exploratory study

Objective

Conditioned pain modulation (CPM) has been found to be inefficient in patients with chronic pain. Animal and human studies showed that CPM is involved in acupuncture analgesia. This study explored the relationship between the potency of CPM and the extent of acupuncture analgesia.

Materials and methods

Thirty-five (35) participants with chronic non-specific low back pain or knee osteoarthritis were given sessions of acupuncture treatment at the pain sites twice per week for four weeks. Participants were asked to complete a diary, before and after the treatment, to monitor changes in clinical pain intensity, daily pain duration and analgesic intake. The potency of CPM was assessed before and after the treatment course. Correlation between potency of CPM and extent of acupuncture analgesia was analysed.

Results

Clinical average pain intensity (0.79 ± 1.09, p < 0.01), daily pain duration (1.45 ± 3.77 hr, p = 0.03) and analgesic intake (1.41 ± 3.96, p = 0.04) decreased significantly after treatment, while potency of CPM increased significantly (18.21 ± 49.94%, p = 0.04). Pearson correlations showed those with less efficient baseline CPM presented with better pain reduction after treatment. Those with less efficient baseline CPM were associated with greater improvement in potency of CPM after treatment (r = 0.60, p < 0.01). There was no association between the change in potency of CPM and the change in clinical pain intensity.

Conclusions

Individuals have varied acupuncture analgesia. People with less efficient baseline CPM would likely benefit from local acupuncture with greater pain relief and improved potency of CPM. Larger studies with a control arm are needed to confirm these results.