Shock Wave Learning

Researchers and clinicians met March 3 in Kentucky to exchange ideas about a treatment that is gaining nationwide attention for its success in healing difficult soft tissue and bone injuries. Extracorporeal shock wave therapy (ESWT) has intrigued many leading U.S. practitioners, not only because of its effectiveness, but because the reason it works is not yet completely understood.

The Equine Musculoskeletal High-Energy Shock Wave Therapy Symposium attracted current ESWT users and also those considering investment in the units. Equine Services, PSC, in Simpsonville, Ky., hosted the event, which was co-sponsored by Focus It and Storz Medical AG.

Othmar Wess of Storz Medical AG in Switzerland first presented the phy-sics and technology behind ESWT. Shock waves are high-energy waves characterized by extremely short build-up times, and are distributed in pressure surges. (For further information see "Waves of the Future" on page 57.)

Jack Snyder, DVM, PhD, Dipl. ACVS, of the University of California, Davis, shared results from evaluations in the clinic and from using ESWT on horses at the 2000 Sydney Olympics. ESWT has shown positive results in the treatment of chronic suspensory ligament lesions and metacarpal stress fractures at UC Davis, with very few adverse side effects. "Since August of 1999 (when he started using ESWT), I haven't done a single surgery on a stress fracture," explained Snyder, who uses "focused" ESWT. "I think that's a sign. The number of cases we're getting is rising exponentially."

Since there is a known analgesic effect on treated horses, ESWT treatment has been regulated by the Federation Internationale Equestre, the international governing body for equine competition. At the Olympics, ESWT treatments were allowed up until three days before competition. Snyder showed images of several success stories in different competition venues at Sydney. "I would not treat any tendon injuries before competition," said Snyder. "The cases we treated were chronic suspensory injuries (no fresh injuries)," which responded favorably. Snyder will be researching the analgesic effect of ESWT with a forceplate treadmill so data can be collected objectively.

Scott McClure, DVM, PhD, Dipl. ACVS, Assistant Professor of Equine Surgery at Iowa State University, has significant experience using focused shock wave units. Through multiple studies, he has been putting the pieces together as to why ESWT works. "Shock waves do disrupt endosteal vasculature (in the connective tissue lining the bone marrow)," he explained. "We're seeing cavitation vessels (spaces or bubbles in the bone caused by disruption) that haven't been identified in cortical bone before. Exactly what they do, we don't know."

McClure has had luck with treatment of 16 navicular cases. At a six month follow-up, ten of the horses had a one-grade improvement in lameness, two improved by two grades, two horses showed no change, and two had no follow-up.

Darryl Bonder, DVM, of Toronto Equine Hospital in Ontario, uses a radial unit and sees potential in using the technology for treatment of foals with limb deformities. "When you have a foal with angular limb deformities, it's often one side of the growth plate that grows faster than the other," Bonder explained. "The limb is no longer straight. So why not try ESWT as growth acceleration on the slower side?"

Following the presentations and a short panel review of case studies, attending practitioners traveled to Equine Services' Surgical Hospital to observe ESWT treatments.

The jury is still out on ESWT and why it works, but with such notable growth in interest and use, researchers might come to conclusions in short order. "What we have here is something that's come along and looks pretty revolutionary," said Snyder.

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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