This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson.
The effects of electrical currents on early wound healing are well known and studied. The possibility that stimulation of bone formation could be induced with a pulsed electromagnetic field (PEMF) was investigated in the 1960s and translated into clinical use by the 1970s. But the clinical use of PEMF for tendon disorders has not met with similar success.
The precise mechanisms by which these fields affect different tissues is easier to study with the tools we have available today. The measurable parameters of PEMF are intensity, duration, frequency, and duty cycle (percent of time the field is on). Nevertheless, many questions about the possible adverse effects of these fields, their focal delivery, and their possible clinical applications remain unanswered.
In a study of human tendon cells, researchers artificially induced inflammatory cues in cultures using different concentrations of IL‐1β.1 When 1 ng/mL of IL‐1β was used, subsequent cytokine and metalloprotease expression was measured at 1, 2, 3, and 7 days after various PEMF exposures.
The PEMF exposure parameters that most evidently decreased the production of IL-6 and tumor necrosis factor-α (TNF-α) were 4 mT, 5 Hz, and a 50% duty cycle. Those same parameters decreased the expression of TNFα, IL-6, IL-8, COX-2, MMP-1, MMP-2, and MMP-3, while at the same time increasing gene expression of the anti-inflammatory proteins IL-4, IL-10, and TIMP-1. However, the combination of 5 mT and 50% duty cycle had a negative impact on cell viability.
These preliminary results may help guide future investigations, but the authors note that the parameters for optimal PEMF effectiveness on tendon cells may vary with time from insult, further complicating the selection of field parameters.
Reference
- Vinhas A, Rodrigues MT, Gonçalves AI, Reis RL, Gomes ME. Pulsed Electromagnetic Field Modulates Tendon Cells Response in IL-1β-Conditioned Environment. J Orthop Res. 2020 Jan;38(1):160-172. doi: 10.1002/jor.24538. Epub 2019 Dec 10.
