ABSTRACT
Objective To evaluate the effects of pulsed ultrasound at different intensities on the healing of standardized contusions in an animal model. Methods Forty-eight 3-month-old, male Sprague-Dawley rats were given experimental contusions of the right gastrocnemius muscle before being divided into four groups randomly ( n =12 in each group): (1) a muscle injury control group (muscle injury without treatment); (2) a muscle injury and pulsed ultrasound (0.25 W/cm2 ) group; (3) a muscle injury and pulsed ultrasound ( 0.5W/cm2 ) group; and (4)a muscle injury and pulsed ultrasound ( 0.75 W/cm2 ) group. Pulsed ultrasound treatment ( frequency 3 mega Hz)was started 24 hours post injury and delivered 5 min daily for 14 days on the injured right hindlimb. At days 4, 7 and 14 after injury, muscle samples were analyzed through hematoxylin-eosin staining and immunohistochemistry for the detection of muscle satellite cells and desmin. Results The average optical density (IOD) of desmin-positive mononucleated cells had increased significantly at days 4, 7 and 14 post injury in the treatment groups compared to the control group, but with no statistically significant difference among the 3 ultrasound treatment groups. Conclusions The pulsed ultrasound treatment played a beneficial role in skeletal muscle regeneration after contusion. There was no significant dose-dependent effect over the intensity range of 0.25-0.75 W/cm2.