Shockingly Effective Part 2

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

From The American Quarter Horse Journal

This is the second in a two-part series. Want to review Part 1?

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. Veterinarians charge by the wave, and the cost ranges from 20 to 40 cents per shock. An average treatment takes 1,000 to 2,000 waves, which brings treatment cost to $200 to $800. Because the machine and training have become more accessible to veterinarians, finding a veterinarian with the skill to treat your horse has become easier. The easiest way to locate one is to ask your American Association of Equine Practitioners-member veterinarian or call your nearest university or large-animal clinic.

The Procedure

The shock-wave therapy procedure is done on an outpatient basis while the horse is standing, although the horse is usually tranquilized for the safety of those working around it.

“Different horses accept it or tolerate it to varying degrees,” says Dr. David Orton, a veterinarian practicing at Clovis Equine Center in Clovis, New Mexico.

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The area to be treated is prepped, which might involve clipping the hair. Once cleaned thoroughly, a transducer gel is applied to the skin and to the head of the machine to make a connection, similar to an ultrasound machine.

The treatments themselves are fairly quick, usually lasting less than 20 minutes. The number of treatments required depends on the problem and its severity. According to Dr. Orton, two to three treatments are standard. The shock waves promote healing, but even those using them are unsure why.

“We don’t know the exact mechanism of healing,” Dr. Scott McClure, a veterinarian and assistant professor at Iowa State University, says. “One thing that is consistently seen is neovascularization, which is new blood vessel in-growths. That’s something that is consistently seen in a number of different studies, but we don’t know what leads to the neovascularization.”

Dr. Orton, who has more than 22 years of experience as a veterinarian and has used a shock-wave machine for more than two years, agrees.

“We can see that it works and see the results, but it’s a difficult thing to specifically define and explain,” he adds.

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Initial studies show that the main mechanism causing it to work is the neovascularization – increased blood flow – as well as an activation of bone growth factors, such as bone morphogenic protein.

More studies are needed to determine the exact process. But before shock-wave therapy is even considered, a veterinarian should go over the horse thoroughly to pinpoint the horse’s injury or lameness.

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“Make sure you’re treating the right thing,” McClure says. “That may sound stupid, but you’ve got to know what you’re treating. You have to know the specific problem and if it’s something that’s shock-wave treatable or not and if it’s likely to respond to the treatment. The treatment isn’t all that complicated, but the big thing is having a good veterinarian who can identify the problem and know what to treat and what not to treat.”

Once the horse has been treated, rest and recuperation are in order.

“We still have to go through rehab,” McClure says. “You can’t just shock a horse and put it back (in training) thinking it’s healed. It just doesn’t work that way.”

Another problem facing shock-wave therapy is the analgesic, or numbing, effect it can create. The effect is not a full numbing like a chemical block but more of a partial decrease in pain perception.

There is some inflammation in the nerves in the treated area. Humans who have undergone the treatment report an initial decrease in pain lasting several days before the pain returns; the pain gradually decreases as the problem heals. Research at ISU found the analgesia to last about four days after treatment. Louisiana State University researchers tested with radial shock-wave treatment and found it caused a numbing effect as well.

Dr. Orton relates several cases in which he used shock-wave therapy to help old injuries.

“I think some of the most rewarding and surprising cases that I’ve had luck with are treating old injuries that created a lot of scar tissue,” he says. “You had a lot of restriction in motion based on the body’s production of an exuberant amount of scar tissue. It’s amazing what I could do as far as breaking down scar tissue and adhesions, and increasing the mobility of previously scarred muscles and tendons. Some of the most rewarding are the ones that I initially thought were helpless or untreatable. I thought, well, from what I know about it, this is a good treatment for those tough things that nothing else works for. And that’s really what it is.”