Shockingly Effective

Courtesy of America’s Horse Daily

Shock wave therapy is helping horses heal quicker from various injuries.

Your prized futurity prospect is enjoying a romp in his paddock after a particularly good training session. When you head out to bring him back in, visions of perfect turnarounds dance in your head. Until you see him wandering your way.

“Oh, no,” you think to yourself. “Is he off?”

Maybe it’s a suspensory injury, bowed tendon or just a bucked shin – injuries that happen to equine athletes all the time. Not career ending, they can mean long lay-ups and the loss of precious training time. A new treatment, however, could change that recovery time from months to weeks.“The way I summarize it,” says Dr. Scott McClure, a veterinarian and assistant professor at Iowa State University and a leading researcher of shock wave therapy, “is you are doing the same thing as time will do – you are just moving time along faster.”

What It’s Good For
Because the therapy is still in the infant stages, its precise use is still being defined. While experimentation is ongoing, its effectiveness has been established in several types of injuries.

Its initial use was in bone-related diseases, such as bone spavins (a degenerative joint disease or osteoarthritis of the hock) and navicular syndrome, which have no other treatment recourses. Despite how its name sounds, it does not use electricity, but instead uses acoustic pressure waves directed into tissue and bone to encourage blood flow and speed healing. It is gaining popularity but is usually used only when more conventional methods are exhausted. It can be beneficial to everything from soft tissue to bone injuries, including stress fractures in the cannon bone, suspensory ligament injuries, bowed tendons, navicular syndrome, bone spavin and back pain.

One study shows that 85 percent of a group of horses with bone spavins improved at least one lameness grade after treatment.

“In a horse with just-bucked shins, my objective is to keep training that horse,” Dr. McClure says. “What we would like to do is to get those shins healed without having to come out of training for an excessive period of time. So when I treat those, I treat them three times at three-week intervals. I treat them the first time, and then they walk for a week and then train for two weeks. Then they get the second treatment and cycle through that three times. Hopefully, we’re able to keep that horse going and never have to actually take him out of training.”

Unfortunately, in the case of degenerative diseases, the treatment merely slows the process.

“We’re not getting rid of the underlying disease,” Dr. McClure says. “What we’re doing is basically covering it up. Navicular is a slow, progressive disease, so all we can do is delay the progress. We don’t have a mechanism to completely get rid of the situation.”

There are some problems and illnesses the treatment is inappropriate for. Shock wave therapy should not be used on infections or tumors. It should not be used around the chest of air-filled structures or on epiphysical growth plates.

How It Works
Doctors began using shock wave therapy in humans several decades ago as a nonsurgical way to treat kidney stones, a process known as lithotripsy. The pressure waves break up the stones, allowing them to pass. Tests in animals began in the mid ’80s, and shock wave machines were first imported into the United States from Europe in the late ’90s. The machines were initially large and cumbersome but have become smaller and easier to use. They have also become more affordable. When first offered, they cost approximately $250,000. They have now dropped to a more affordable range, around $40,000.

The machine consists of a body that generates the shock wave and the head, which administers it. It is similar to ultrasound but uses a lower frequency that can be focused at a specific site within the body. Little of the wave is absorbed by the tissue, and it produces no heat.

The supersonic acoustic pressure waves created by the machine last only nanoseconds. They travel through the head of the machine, which is what focuses them into the horse’s body, nearly uninterrupted, through fluid and soft tissue. Their effect occurs at places where there is a change in the type of tissue, such as between soft tissue and bone.

There are two types of shock wave generators. The first is a nonfocused (radial) shock wave unit, which creates a wave that radiates the shock like a pebble dropped in a pond.

The second method, which is the more effective and most commonly used, is a focused shock wave unit that creates a wave that is focused to a point, using lenses or parabolic reflectors, and concentrates the effect of the waves.

There are three ways shock waves are produced in the body of the machine. The first is electromagnetic, which is similar to a stereo speaker. Electricity goes through two different membranes that repel each other, pushing the fluid. The second method is piezoelectric, which uses piezo crystals. When electricity runs through the crystals, they expand rapidly, creating the wave. The final, and most popular, method is electrohydraulic, which uses a spark gap that creates a small vaporization of fluid. The bubble expands and collapses, starting the wave.

The head of the shock wave machine can be changed to direct the wave where it needs to go. The flatter the head, the deeper it goes. The more conical heads focus shallowly, allowing the veterinarian to pinpoint where the wave goes for the greatest level of effect.