Effects of low-voltage microamperage stimulation on tendon healing in rats

STUDY DESIGN: Randomized controlled prospective experimental study. OBJECTIVES: To examine the effects of transcutaneous low-voltage microamperage stimulation (LVMAS) on the mechanical strength of Achilles tendon repair in rats at 4 weeks after injury. BACKGROUND: Understanding the effect of LVMAS on the healing of injured tendons is hampered by the lack of related experimental studies, especially from the aspect of biomechanical outcome measures. METHODS AND MEASURES: Fourteen 3-month-old male Sprague-Dawley rats received surgical transection to the medial portion of their right Achilles tendon. The rats were divided into a LVMAS group (n = 7) and control group (n = 7). From day 6 postsurgery onwards, the LVMAS group received daily treatment of transcutaneous LVMAS (2.5 V, 100 mu A/cm(2), 10 pulses per second, positive current) for a total of 22 sessions, while the control group received placebo LVMAS by the same investigator during that period. On day 31, the Achilles tendons were harvested for biomechanical testing for load relaxation, stiffness, and ultimate tensile strength along the longitudinal direction. RESULTS: The normalized Achilles tendon ultimate tensile strength of the LVMAS group (mean +/- SD, 110.5% +/- 25.0%) was higher than that of the control group (75.3% +/- 20.8%) (P = .014), but no significant difference was found in normalized stiffness and load relaxation between the 2 groups (P = .239 and .350, respectively). CONCLUSION: The results of this study suggest that the administration of transcutaneous LVMAS could improve healing and consequently the tensile strength of partially transected Achilles tendons of rats at 4 weeks after injury.