Effects of pulsed electromagnetic field therapy at different frequencies and durations on rotator cuff tendon-to-bone healing in a rat model.

BACKGROUND: Rotator cuff tears affect millions of individuals each year, often requiring surgical intervention. However, repair failure remains common. We have previously shown that pulsed electromagnetic field (PEMF) therapy improved tendon-to-bone healing in a rat rotator cuff model. The purpose of this study was to determine the influence of both PEMF frequency and exposure time on rotator cuff healing. METHODS: Two hundred ten Sprague-Dawley rats underwent acute bilateral supraspinatus injury and repair followed by either Physio-Stim PEMF or high-frequency PEMF therapy for 1, 3, or 6 hours daily. Control animals did not receive PEMF therapy. Mechanical and histologic properties were assessed at 4, 8, and 16 weeks. RESULTS: Improvements in different mechanical properties at various endpoints were identified for all treatment modalities when compared with untreated animals, regardless of PEMF frequency or duration. Of note, 1 hour of Physio-Stim treatment showed significant improvements in tendon mechanical properties across all time points, including increases in both modulus and stiffness as early as 4 weeks. Collagen organization improved for several of the treatment groups compared with controls. In addition, improvements in type I collagen and fibronectin expression were identified with PEMF treatment. An important finding was that no adverse effects were identified in any mechanical or histologic property. CONCLUSIONS: Overall, our results suggest that PEMF therapy has a positive effect on rat rotator cuff healing for each electromagnetic fundamental pulse frequency and treatment duration tested in this study.