Therapeutic Ultrasound Settings for Horses Identified

Did you know that ultrasound can be used for more than just diagnosing tendon and ligament injuries in horses? Indeed, veterinarians can also use it therapeutically to treat soft tissue injuries, but what settings they should use and how long they should treat an injured horse has, until now, been a bit of a "guesstimation" game.

“The heat produced by therapeutic ultrasound improves the extensibility or stretchiness of collagen fibers in tendons and ligaments, decreases pain and inflammation, reduces muscle spasms, and improves blood flow,” explained Leslie Montgomery, DVM, Dipl. ACVS, from Desert Pines Equine Medical and Surgical Center, in Las Vegas, Nev.

“Target” temperatures for therapeutic ultrasound are already established in human and veterinary medicine; however, the exact settings needed to heat horse tissue to therapeutic temperatures are not yet known.

To determine what ultrasound settings are needed to achieve adequate temperature increases in various equine body parts, Montgomery and colleagues inserted temperature probes into horses' superficial and deep digital flexor tendons (commonly injured tendons located at the back of the cannon bone) and at three different depths in the epaxial muscles that run alongside the spinal column.

Key study findings were:

  • Researchers noted an average temperature increase of 3.5°C (6.3°F) in the superficial digital flexor tendon during a 10-minute treatment session using an ultrasound frequency of 3.3 megahertz (MHz) and an intensity of 1.0 W/cm2 (watts per square centimeter, which means the amount of power in a given area);
  • In the deep digital flexor tendon, the team achieved an average temperature increase of 2.5°C (4.5°F) using the same settings described above;
  • When treatment intensity was increased to 1.5 W/cm2, temperature increases in the superficial and deep tendons were 5.2°C (9.36°F) and 3.0°C (5.4°F), respectively; and
  • The team reported only minimal temperature changes in the epaxial muscles using similar settings with a treatment time of 20 minutes.

“A therapeutic increase in temperature of 2-4°C (3.6-7.2°F) was achieved in both the superficial and deep digital flexor tendons using a 10-minute treatment session with the ultrasound frequency set to 3.3 MHz and the intensity at 1.0 W/cm2," Montgomery summarized. "Ultrasound settings commonly used to treat human muscle were not effective in heating the epaxial muscles.”

She noted that additional points to consider include:

  • The settings found to be effective for equine tendons are available on most therapeutic ultrasound machines in equine practices today;
  • The protocol used to treat an injury with therapeutic ultrasound depends on the injury and should be dictated by an equine veterinarian; and
  • Most protocols begin with daily ultrasounds that then decrease in frequency, depending in the horse's progress.

“The treatment process takes time as most injuries require weeks or months of therapy," Montgomery concluded. "But the results are worth the wait.”

The study, “Muscle and tendon healing rates with therapeutic ultrasound in horses,” will be published in an upcoming edition of Veterinary Surgery. 

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.