Pulsed magnetic and electromagnetic fields in experimental achilles tendonitis in the rat: A prospective randomized study

Abstract

Objective: To investigate the effects of pulsed magnetic fields (PMF) and pulsed electromagnetic fields (PEMF) on healing in experimental Achilles tendon inflammation in the rat. Design: Prospective randomized trial. Setting: University medical school. Methods: Exposure of the Achilles tendon and injury by a weight of 98.24g falling from a height of 35cm in 180 male Sprague-Dawley rats. Intervention: A daily 15-minute session with PMF of 17Hz or 50Hz, or PEMF of 15Hz or 46Hz, or a sham session. Outcome Measures: Random sacrifice 2 hours after the operation, and at 1, 3, 7, 14, or 28 days. Assessment of water content, weight, and histological appearance of the tendons. Results: The time from injury and the various treatment modalities exerted a significant influence on the water content of the tendon after the injury (two-way ANOVA, p = .02). At day 3, the water content of the PEMF 46Hz group was significantly higher than in the other groups, decreasing sharply by day 7 and being similar to the other groups thereafter. By the end of the experiment, the PEMF 15Hz group was not significantly different from the control group. At day 7, the PMF 50Hz group showed significantly lower water content than the control group ( p = .03), but at 14 days the PMF 50Hz group was not significantly different from the control group. PMF 50Hz suppressed the extravascular edema during early inflammation. PMF 17Hz showed a similar initial trend, producing a consistent lower water content throughout the experiment, reaching statistical significance by the end of treatment. By the end of the experiment, the collagen fibers had nearly regained their normal alignment in all groups, with a more physiological alignment seen in the PEMF 17Hz group. Conclusions: The tendon returned to histological normality in all groups, but the PMF 17Hz group showed better collagen alignment by the end of the study. PMF 17Hz resulted in a greater reduction of inflammation, with a better return of the tendon to histological normality. Different PMF and PEMF could be applied according to when treatment is started after the injury. If there is no delay between injury and beginning of pulsed magnetic treatment, PMF17 should be used.