Peripheral magnetic stimulation (PMS) may improve postoperative pain up to 2 months following surgery, according to a systematic review and meta-analysis published in the Journal of Pain.
To determine the potential of PMS for effectively managing postoperative pain, investigators from University of Toronto in Canada searched publication databases through May 2021 for studies using PMS in the setting of postoperative pain. A total of 18 studies were included in this analysis.
The pooled sample size was 958 patients, and the studies were set in the postoperative orthopedic (n=7), plastic (n=6), dental (n=3), spinal (n=1), and caesarean section (n=1) settings.
The PMS interventions had peak magnetic field intensities ranging from 0.005 to 4 mT and frequencies of 40 Hz, 75 Hz, or 27.12 MHz. Interventions were administered daily for 40 minutes to 24 hours, for a duration of 24 hours to 60 days. The comparator control cohort received placebo with sham treatments or no intervention. All but 1 study was a randomized controlled trial.
In the first 7 days after surgery, PMS was reported to have a more beneficial effect on postoperative pain in 10 studies and to have no effect in 8 studies. In the pooled analysis, PMS was associated with reduced pain scores compared with control group scores on a 10-point numeric rating scale (mean difference [MD], -1.64; 95% CI, -2.08 to -1.20; I2, 77%).
At 1 and 2 months after surgery, 2 studies reported an improvement in pain at both 1 and 2 months and 3 studies reported an improvement at 1 or 2 months, but not both. In the pooled analysis, PMS was associated with lower pain scores at 1 month (MD, -1.83; 95% CI, -2.48 to -1.17; I2, 0%) and 2 months (MD, -1.96; 95% CI, -3.67 to -0.26; I2, 84%) compared with control group scores. No significant difference in effects were observed when stratifying by comparator type at 1 month (P =.25) and 2 months (P =.17).
For chronic postsurgical pain, the studies had differing follow-up durations and reported conflicting outcomes. In the pooled analysis, the PMS cohort was not favored over the control cohort for reduced chronic postoperative pain at 6 months (MD, -1.62; 95% CI, -4.06 to 0.83; I2, 89%) or 12 months (MD, -0.54; 95% CI, -5.44 to 4.36; I2, 94%) after surgery. Notably, in a post-hoc analysis, the studies that compared PMS with no intervention reported significant differences, whereas the studies with a sham control group did not (P =.04).
Of the 4 studies that reported postoperative opioid consumption, 2 reported a significant decrease in consumption with PMS compared with the control group. In the pooled analysis, PMS was not favored over the control group for the outcome of opioid consumption (MD, -4.44; 95% CI, -9.19 to 0.30; I2, 100%).
Ten studies reported adverse events, with no significant difference between the PMS and control group conditions reported.
The limitations of this analysis included the high heterogeneity observed in comparisons, the small sample sizes in the studies, and the fact that many studies had high patient dropout.
The study authors concluded, “PMS is a novel non-pharmacologic non-invasive analgesic modality. This review suggests that PMS may be a potentially beneficial adjunct to postoperative pain management.”
Park S, Park R, Westwood D, Moayedi M, Khan JS. Effect of peripheral magnetic stimulation on acute and chronic pain after surgery: a systematic review and meta-analysis. J Pain. Published Online March 4, 2023. doi:10.1016/j.jpain.2023.02.031