Shock Wave Therapy: Use it Logically

Extracorporeal shock wave therapy (ESWT) is an established medical treatment (see The Horse of May 2001). Originally utilized to treat human kidney stones non-invasively, additional applications for this technology have been discovered. ESWT has been used to treat musculoskeletal disease for a number of years in Europe. Recently, the FDA approved ESWT for the treatment of heel spurs in people.

All of this data was generated from studies that used a "focused" shock wave generator, not a pulsed machine. A focused shock wave can pass through tissues without having any effect until it reaches the focal point. The benefit is that the maximum energy is delivered to the site of the lesion being treated. In a recent report from Germany in patients with tennis elbow, 72% of the patients treated with focused shock wave systems improved versus 32% for those treated with an unfocused system.

The wave appears to have multiple effects. There are mechanical effects, such as when shock waves are used to break up kidney stones. There are also cellular effects that we are just beginning to understand. Shock waves can stimulate cells to divide and to produce cytokines, which act as cellular communicators to stimulate cellular metabolism. The final result can be stimulation of neovascularization of bone-tendon junctions and increased bone formation.

Shock wave therapy has some well-defined principles and some applications for which one could logically derive that if it is effective in humans and other animals, it would be beneficial to the horse. Initial clinical results indicate that high suspensory disease and injured bone-tendinous/ligamentous junctions respond to ESWT. Also, stress fractures and fractured splint bones would likely benefit from ESWT. In a limited number of flexor tendon injuries, there is some response to ESWT. (As has been seen in other species, utilizing too high energy levels can actually worsen the problem.)

An example of the application of a focused unit is a stress fracture. These occur at a specific focal area that can be pinpointed by radiographs, ultrasound, and scintigraphy. The objective is to stimulate the fracture to heal by delivering high-energy focused waves directly to the fracture without disrupting any of the surrounding soft tissues that are important in supplying nutrients for the healing process. The question to be answered is: "Will these heal faster if treated than if not treated?" In my opinion the answer is yes. However, we do not have data to support this.

My results treating navicular syndrome have been similar to others using focused shock waves. Approximately 70% of treated horses improved at least one lameness grade. There are multiple things to consider, such as the degree of lameness prior to treatment and the acceptable outcome for a horse. We cannot expect to take an extremely lame horse and make it new again, but we can reasonably expect some improvement in the lameness.

I think we will see controlled studies of the healing of suspensory desmitis and other problems such as stress fractures. Controlled studies are necessary, but hard to complete. It is difficult to do controlled studies in "naturally occurring disease" because there are so many variables in animal care, ancillary treatments, etc. As well, owners don't want their horses in the "control group," they want their horses treated. We can have research studies where the horses are controlled by the investigator. However, this is expensive. Horse owners and businesses have been very supportive of controlled scientific studies in the past, as have organizations such as Morris Animal Foundation, the AQHA, and the Grayson/Jockey Club Foundation.

There is a well-documented analgesic effect of ESWT. This effect is short-lived and the mechanism of the effect is unknown. One must be concerned that this analgesic effect can make a horse appear less lame for a short period of time while the lesion is still present. This puts horses at risk of more serious injuries while working on an injured leg. We must make sure that this does not occur. The FEI has placed a seven-day ban prior to competition for horses receiving shock wave treatment.

In my experience, it would appear that ESWT has a place in equine practice. It will take time to develop appropriate techniques and validate its use. However, we must continue to use what we already know about ESWT and apply it logically to the horse.

About the Author

Scott R. McClure, DVM, PhD, Dipl. ACVS

Scott R. McClure, DVM, PhD, Dipl. ACVS, is Assistant Professor of Equine Surgery at the College of Veterinary Medicine at Iowa State University. Since presenting a paper on ESWT at the 2000 AAEP Convention, he has continued with shock wave research and has written several more papers on the topic.

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