FROM RHEUMATOLOGY
A wearable pulsed electromagnetic fields device reduced pain intensity and improved physical functioning in patients with painful knee osteoarthritis (OA) in a double-blind, randomized trial.
The commercially available device ( ActiPatch , Bioelectronics Corp.) did not improve patients’ mental health, but significantly reduced patients’ intake of NSAIDs and analgesics, compared with placebo.
“Although NSAIDs remain the gold standard for the treatment of pain in OA, there is increasing need to find conservative and alternative approaches, in order to avoid the toxicity associated with the chronic use of the analgesics, mostly in the elderly population,” wrote Dr. Gian Luca Bagnato of the University of Messina (Italy) and his colleagues ( Rheumatology [Oxford]. 2015 Dec 24. doi: 10.1093/rheumatology/kev426 ).
Pulsed electromagnetic fields (PEMF) therapy has been shown to reduce chondrocyte apoptosis and MMP-13 expression of knee cartilage and favorably affect cartilage homeostasis in animal models, but data regarding osteoarthritis (OA) pain and function in humans are mixed.
A recent systematic review found no effect in all 14 trials analyzed, but when only high-quality randomized clinical trials were included, PEMF provided significantly better pain relief at 4 and 8 weeks and better function at 8 weeks than did placebo ( Rheumatology [Oxford]. 2013;52[5]:815-24 ).
Not only has the quality of trials varied, so has the PEMF pulse frequency and duration used in trials, “further limiting the possibility of comparing efficacy and safety,” Dr. Bagnato and associates observed.
The current study evenly randomized 60 patients with radiologic evidence of knee OA and persistent pain to wear the PEMF or a placebo device for a minimum of 12 hours, mainly at night, with the device kept in place with a wrap. The active device emits a form of non-ionizing electromagnetic radiation at a frequency of 27.12 MHz, a pulse rate of 1,000 Hz, and a burst width of 100 microsec.
Persistent pain was defined as a minimal mean score of 40 mm for global pain on the VAS (visual analog scale) and daily pain during the month prior to enrollment despite maximal tolerated doses of conventional medical therapy, including acetaminophen and/or an NSAID. The patients’ mean age was 67.7 years and mean OA duration 12 years.
The primary efficacy endpoint was reduction in pain intensity at 1 month on the VAS and WOMAC (Western Ontario and McMaster Universities Arthritis Index). The mean WOMAC total score at baseline was 132.9.
At 1 month, VAS pain scores were reduced 25.5% with the PEMF device and 3.6% with the placebo device. The standardized treatment effect size induced by PEMF therapy was –0.73 (95% confidence interval, –1.24 to –0.19), the investigators reported.
WOMAC pain subscale and total scores fell 23.4% and 18.4% with the PEMF device versus a 2.3% reduction for both scores with the placebo device. The standardized effect size was –0.61 for WOMAC pain (95% CI, –1.12 to –0.09) and –0.34 for WOMAC total score (95% CI, –0.85 to 0.17).
At 1 month, the mean Short Form-36 physical health score was significantly better in the PEMF group than in the placebo group (55.8 vs. 53.1; P = .024), while SF-36 mental health scores were nearly identical (43.8 vs. 43.6; P = .6).
Patients were allowed per protocol to take prescribed analgesic therapy as needed, but eight patients from the PEMF group stopped these medications, while one patient from the placebo group stopped medication and three started a new therapy for chronic pain. No adverse events were reported during the study.
“Given that our data are limited to a low number of participants and the long-term efficacy of the wearable device is unknown, the generalizability of the results needs to be confirmed in a larger clinical trial with a longer duration of treatment,” Dr. Bagnato and his coauthors concluded. “However, the use of a wearable PEMF therapy in knee OA can be considered as an alternative safe and effective therapy in knee OA, providing the possibility for home-based management of pain, compared with previous studies.”
