Therapeutic ultrasound improves strength of achilles tendon repair in rats.

The purpose of this study was to evaluate the effects of therapeutic ultrasound on structural properties and functional performance of Achilles tendon healing. Thirty Sprague-Dawley rats with surgical hemitransected Achilles tendon were studied. Ten were treated daily with 1 MHz continuous ultrasound at 1.0 W/cm2 for 4 min, 11 at 2.0 W/cm2 for 4 min and nine served as control without treatment. Achilles functional index (AFI) was recorded preoperatively and on postoperative days 3, 10 and 30. On day 30, the rats were sacrificed and Achilles tendons were tested for load-relaxation, stiffness and ultimate tensile strength (UTS). Results showed that UTS of both low-dose (p=0.023) and high-dose (p=0.002) groups was significantly greater than in controls. No significant differences in AFI (p=0.179), load-relaxation (p=0.205) and stiffness (p=0.842) were found among groups. These findings suggested that both low- and high-dose therapeutic ultrasound accelerate the healing process of ruptured tendon.