Extracorporeal shock wave therapy (ESWT) has become an emerging new technology for treating musculoskeletal problems, soft-tissue
injuries and bone injuries in horses. ESWT is non-invasive, used to stimulate healing to return horses to a level of fully
sound, useful activity without recurrence of disease.
From outside the body (extracorporeal), the machine generates high-intensity shock or pressure waves, which pulse to a specific
site within the injured tissue. Though its actual mode of action is still in dispute, it stimulates and accelerates the healing
process, essentially combining an immediate analgesic effect with a reduction in inflammation, neovascularization in soft
tissue and osteogenesis in bone. According to Dr. Scott McClure, DVM, Iowa State University, a leading researcher in the field,
it can be used to treat various conditions, such as suspensory ligament desmitis, navicular disease, saucer fractures, bucked
shins, bowed tendon, sesamoid fractures, stress fractures and vertebral spinal pain (kissing spine lesions).
Though some of its initial use came with the need for general anesthesia, the most common units today are portable and able
for use with a standing horse in the barn or at the racetrack.
The handheld wand of the unit attaches to an energy source. For the simplest shock wave procedure, the horse is lightly sedated;
the area to be treated is shaved to provide for good contact; a contact gel is placed on the horse's skin, and the hand unit
is applied to the horse to deliver the shock wave pulses. The treatment takes minutes. The horse does not experience pain.
Sedation is recommended so the horse remains still so the treatment is applied accurately, targeted to the specific treatment
location, and if fractious, the veterinarian is protected.
Dr. Scott McClure of Iowa State's School of Veterinary Medicine reports ESWT can be used in the treatment of various bone
injuries. For the simplest procedure, the horse is lightly sedated; the area for treatment is shaved to provide good contact;
a contact gel is placed on the horse's skin, and the hand unit is applied to the horse to deliver shock wave pulses.
Electrical energy is used to initiate the pressure wave. The energy settings and the number of pulses are important. Too low
energy or too few pulses might not create the desired therapeutic effect. Excessive energy or pulses may result in tendon
damage. The pressure waves penetrate fluid and soft tissue, and their effects occur at sites at the bone/soft tissue interface.
The mechanism by which shock waves stimulate healing is unknown. Theoretically, shock waves can increase cellular membrane
permeability, cellular division, and stimulate cytokine production by bone marrow, neovascularization of soft tissue and osteogenesis
in bone. Pressure waves might help physically break down or move a hematoma or fluid from the lesion to allow the fibroblasts
to more rapidly fill the defect. At this time, the effect of ESWT on disease recurrence and future ligament strength has not
Today, the units have flexible therapy heads — similar to an ultrasound wand on a long chord — to be applied across the horse's
body to any anatomical site.
Though the horse is sedated, it can tolerate the pain, similar to hitting the funny bone, and there is some numbing effect
as the shock waves are applied. Depending on the site and injury depth, the usage is usually 1,500 to 2,500 impulses. A small,
defined area requires fewer impulses than a larger surface area. The more shallow and softer the tissue, fewer and milder
impulses are required; the deeper and harder the tissue, the greater the number of impulses and energy required. Though shock
wave therapy works with good results, there is need to define the procedural protocols, including how to treat, at what intensity,
at what energy level and the proper number of impulses.
"During the procedure, we do sedate the horses and either use a twitch or sometimes use local anesthetic at the site," says
David McCarroll, DVM with Interstate Equine Hospital in Goldsby, Okla.