Background: Meniscal tears in the avascular region are thought to rarely heal and are a considerable challenge to treat. Although the therapeutic effects of a pulsed electromagnetic field (PEMF) have been extensively studied in a variety of orthopaedic disorders, the effect of a PEMF on meniscal healing has not been reported.
Hypothesis: PEMF treatment would promote meniscal healing and prevent osteoarthritis progression.
Study design: Controlled laboratory study.
Methods: A total of 72 twelve-week-old male Sprague-Dawley rats with full-thickness longitudinal medial meniscal tears in the avascular region were divided into 3 groups: control (Gcon), treatment with a classic signal PEMF (Gclassic), and treatment with a high-slew rate signal PEMF (GHSR). Macroscopic observation and histological analysis of the meniscus and articular cartilage were performed to evaluate the meniscal healing and progression of osteoarthritis. The synovium was harvested for histological and immunofluorescent analysis to evaluate the intra-articular inflammation. Meniscal healing, articular cartilage degeneration, and synovitis were quantitatively evaluated according to their scoring systems.
Results: Dramatic degenerative changes of the meniscus and articular cartilage were noticed during gross observation and histological evaluation in Gcon at 8 weeks. However, the menisci in the 2 treatment groups were restored to normal morphology, with a smooth surface and shiny white color. Particularly, the HSR signal remarkably enhanced the fibrochondrogenesis and accelerated the remodeling process of the regenerated tissue. The meniscal healing scores of the PEMF treatment groups were significantly higher than those in Gcon at 8 weeks. Specifically, the HSR signal showed a significantly higher meniscal repair score than did the classic signal at week 8 (P < .01). Additionally, the HSR signal significantly downregulated the secretion levels of interleukin 1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) in the meniscus and synovium as compared with the control group. When compared with the 2 treatment groups, Gcon had significantly higher degeneration scores (Gcon vs Gclassic, P < .0001; Gcon vs GHSR, P < .0001). The HSR signal also exhibited significantly lower synovitis scores compared with the other two groups (Gcon vs Gclassic, P < .0001; Gclassic vs GHSR, P = .0002).
Conclusion: A PEMF promoted the healing of meniscal tears in the avascular region and restored the injured meniscus to its structural integrity in a rat model. As compared with the classic signal, the HSR signal showed increased capability to promote fibrocartilaginous tissue formation and modulate the inflammatory environment, therefore protecting the knee joint from posttraumatic osteoarthritis development.
Clinical relevance: Adjuvant PEMF therapy may offer a new approach for the treatment of meniscal tears attributed to the enhanced meniscal repair and ameliorated osteoarthritis progression.
Keywords: avascular region; knee; meniscal tears; pulsed electromagnetic field (PEMF).