Comparing therapeutic ultrasound with microamperage stimulation therapy for improving the strength of Achilles tendon repair.

In exploring the effects of therapeutic ultrasound (US) and microamperage stimulation (MAS) on the biomechanical performance of repairing Achilles tendon in rats, 35 Sprague-Dawley rats receiving surgically induced injury to their right medial Achilles tendon were studied. The rats were divided into four groups of low-dose US (group 1, n = 10), high-dose US (group 2, n = 11), MAS (group 3, n = 7), and control (group 4, n = 7). The treatment started on day 6 after injury. Groups 1 and 2 received 4 min of daily US treatment at 1.0 and 2.0 W/cm(2), respectively. Group 3 received 30 min of daily transcutaneous MAS treatment. Group 4 received 30 min of daily sham MAS treatment. On day 31, the Achilles tendons were mechanically tested. Data on the right side were normalized to the left side and analyzed with MANOVA with α = 0.05. Results of MANOVA was significant and post hoc tests revealed that the normalized strength of groups 1, 2, and 3 were higher than that of group 4 (p = 0.003) but no significant difference was found among the treatment groups. The ANOVA result of the normalized load relaxation and stiffness was p = 0.06 and p = 0.07, respectively. These findings suggested that both low/high doses of US and MAS therapies could improve the strength of Achilles tendon but in view of its short treatment time, US is considered to be more efficient than MAS for improving the strength of the repairing tendons.