Doctors originally used shockwave therapy more than 20 years ago to disintegrate kidney stones in their patients, then learned that the therapy can also treat tendonitis, tennis elbow, heel spurs and other ailments. Equine researchers are still uncovering everything shockwave therapy can do for horses after it was initially and successfully used in Germany in 1996 to treat lameness. Shockwaves are high-pressure, low-frequency sound waves generated by a device outside the body and focused on a specific body site. When the shockwaves meet tissue interfaces of different densities, the energy contained in the shockwaves is released and interacts with the tissue, triggering natural repair mechanisms and stimulating bone formation and blood flow.
The shockwaves can lessen or eliminate pain and accelerate healing. New York trainer Rick Schosberg has a unique perspective on shockwave therapy. He’s used it on himself and his horses. “I’ve used it for myself for tennis elbow; it helped my elbow for 90 days,” Schosberg said. “With my horses I’ve used it a couple times on injuries and it did okay for minor injuries, soft tissue and saucer fractures. It probably knocked a third off the healing time but it’s expensive. You use it for at least three treatments over a month and a half, usually every two or three weeks. As long as it‘s not abused it’s okay. You can‘t run a horse within 10 days after you use it and you have to report it every time you use it (in New York) because it has an analgesic effect.” Shockwave therapy’s impact on horse racing could not have happened if it wasn’t developed for human patients first. And that happened by accident. During experiments with high-velocity projectiles, which were being used to smash ceramic plates, an employee at a company in Germany touched the plate at the very moment the projectile hit the plate. He felt something in his body akin to an electric shock, though measurements showed that there was no electricity present. That prompted German scientists to begin researching the possible effects of shockwaves on humans in the late 1960s. The first successful disintegration of a kidney stone in a patient by shockwaves was done in 1971. Fourteen years later, experiments were conducted regarding the effect of shockwaves on bones, leading to experiments on other parts of the human anatomy.
Today, shockwaves are the first choice of treatment for kidney and ureteral stones and has morphed into treatment for other medical conditions. Will equine medicine’s use of shockwaves follow a similar pattern? The first equine disease to be treated with shockwaves was proximal suspensory desmitis, an injury to the suspensory ligament which is a major cause of lameness. A year later, shockwaves were used on a horse with Navicular Syndrome, an ailment affecting the small navicular bone in a horse’s foot and the connecting ligament. The first use of shockwaves in the United States happened in 1998 with a horse with a distal hock joint and navicular pain. All the results were encouraging. “When we first started using it, it worked okay on lameness,” Iowa State University’s Dr. Scott McClure, DVM, a leading researcher of equine shockwave therapy, said. “At this point in time, it’s been well documented for tendon and ligaments.
A lot of people think it works for stress fractures. I think there are some joint applications which we’re learning more about. Soft tissue, too. It’s been shown to increase permeability of cell walls.” He believes that increased cell wall permeability could lead to drugs which are more effective attacking tumors. “There’s potential for a lot of applications,” McClure said. “I clearly don’t think we understand all of its uses.” There are two types of equine shockwave therapy: extracorporeal generated outside the body and focused on a specific area of a horse’s body, and radial pressure waves when an applicator is pressed on the horse’s body. “The two of them get lumped together, but they shouldn’t be,” McClure said. “They’re very different. Radial pressure waves have lower pressure and more shallow penetration.” According to Dr. Stephen Adams of Purdue University‘s Veterinary Teaching Hospital in a 2002 article, studies have shown that shockwave therapy is effective treating suspensory ligament disease, bowed tendons, ringbone, bone spavin, splints, fractured splint bones, sore backs, navicular syndrome and fractures not healing properly. “Initial studies show that about 75 percent of horses treated for these conditions show marked improvement following shockwave therapy,” Adams wrote, while noting that many conditions require a second treatment to produce optimum results. “Advantages of this treatment are that no drugs are used, and horses with chronic conditions such as bone spavin, chronic suspensory ligament disease and navicular syndrome can continue to exercise.
Frequently, improvement in lameness is achieved in horses where conventional treatments have failed. Shockwave therapy is used as an adjunct treatment for fresh injuries such as recent bowed tendons with the goal of reducing convalescent time and improving the outcome.” On its website, the University of Wisconsin-Madison’s Veterinary Medical Teaching Hospital suggests using shockwave therapy on horses suffering from: suspensory ligament injury, tissue calcification, fractures or joint ankyloses, fatigue injury to bone, back pain, navicular disease and bone exostosis.
McClure documented the effect of extracorporeal shock wave therapy (ESWT) on horses with unilateral forelimb lameness in a study he co-authored with Jessica Dahlberg, Richard Evans and Eric Reinertson which was published in the July 1st, 2006 issue of the Journal of the American Veterinary Medical Association. The study focused on five geldings and four fillies and mares with lameness.
Treatment by ESWT resulted “in a period of acute improvement in lameness severity that typically persists for two days. Thus, in horses undergoing ESWT, exercise should be controlled for a minimum of two days after treatment to prevent further injury.” The reason is that ESWT has an undeniable analgesic effect. “This has raised concerns that use of ESWT to treat musculoskeletal injuries in horses may, because of the analgesic effects, result in overuse of the injured limb, causing further injury to the affected part and posing a risk to treated horses and their riders,” the study said. “For this reason, racing jurisdictions in the United States and the Federation Equestre International have adopted regulations that require a 5-to-7 day period after treatment before the horse is allowed to perform.”
Regardless, the horseracing industry, one never known to embrace change and new products, has quickly come on board in using this non-invasive treatment on their horses. “Over the last five years, it’s dramatically increased,” McClure said. “The market is starting to saturate. There’s a lot of equipment out there. In 1988, I had the second machine in the country. I think the owners and trainers have taken the bit and run with it. They’ve been very aggressive with that.” Trainer Sanna Hendricks used shockwave therapy on her multiple stakes winning steeplechaser Praise the Prince after he suffered a soft tissue injury below the pastern while winning the 2003 Grade 1 New York Turf Writers’ Cup at Saratoga Race Course. “We used shockwave therapy on him, and he responded to it,” Hendricks said in an August 30th, 2004 story in the Blood-Horse. “I took the conservative approach with him. I gave him plenty of time to rest and recover and didn’t bring him back to training until February 5th with an eye on these races at Saratoga.” Praise the Prince not only made it back to the races at Saratoga, he won the 2004 Grade 2 A.P. Smithwick Memorial Steeplechase there as a nine-year-old. If that isn’t an endorsement for shockwave therapy, what is? But shockwaves should not be construed as a panacea.
Complications can occur with incorrect use, and McClure wrote, “The release of kinetic energy at interfaces of different acoustic impedances is crucial in planning ESWT. Shock waves must never be focused on gas-filled cavities like the lung or intestine.” Meanwhile, he’s back at work, doing new studies to see just what else shockwave therapy may help.