Comparison of therapeutic ultrasound and exercises for augmenting tendon healing in rats.

We compared therapeutic ultrasound (US) and exercises on Achilles tendon healing in 49 mature male rats. The medial Achilles tendon of the right leg was transected and the rats were divided into five groups: 1. control (n = 9), 2. 1 W/cm(2) US (n = 9), 3. 2 W/cm US (n = 10), 4. running (n = 11) and 5. swimming (n = 10). All animals were treated daily, starting from postsurgical day 5, according to their group assignment, except for group 1 control. Achilles functional index (AFI) was recorded pre- and postoperatively. On day 30, the Achilles tendons were biomechanically tested. Results revealed that groups 3 and 4 had higher tensile strength than the controls (p = 0.037 and 0.034), but groups 2 and 5 were not different from the controls. No significant difference in stiffness (p = 0.21) or AFI (p = 0.22) was found. These findings suggest that therapeutic US treatment at 2 W/cm(2) and running exercise improved the strength of repairing Achilles tendon.