Shockwave: Waves of the Future

A new method of treating orthopedic injuries in horses is gaining interest among veterinarians and horse owners. Veterinarians around the world are using extracorporeal shock wave therapy (ESWT) and are encouraged by the results they are seeing with this technology. This article will summarize current research and applications of ESWT in human and veterinary medicine. Additionally, I will share some of my own experiences with equine cases.

Leading members of the veterinary community met in early March in Simpsonville, Ky., to discuss the latest in ESWT treatment findings and to introduce the technology to veterinarians interested in employing the therapy in their own practices. For more information on the Equine Musculoskeletal High-Energy Shockwave Therapy Symposium, see the news item in this month's NewsFront section.

What Is ESWT?

Extracorporeal shock waves are energy waves that are transmitted through the skin into deeper anatomical structures. The waves are characterized by high positive pressures, and their energy is transmitted through the skin and underlying soft tissues with little to no harmful effect to the superficial tissues. The energy of the waves predominately is deposited within bone and soft tissues (as in high suspensory ligament injuries). Although the exact medical process is not clear, it appears that when the shock waves' energy is delivered, two things occur: 1) A transient period of pain relief (analgesia), and 2) An eventual increased rate of bone and tissue remodeling (healing). Because of these effects, ESWT has gained considerable attention for the promotion of healing and remodeling musculoskeletal injuries.

Several types of machines are used currently for ESWT. Therefore, results seen with one machine type might not necessarily apply for other machine types. A debate currently exists regarding the importance of using an ESWT machine that focuses the shock waves. "Focused" machines create a fundamentally different wave than a "radial head" emits. While both types of machines create "pressure gradient waves," the focused units create waves that focus on a specific point. Focused shock wave machines are larger and more expensive than machines that emit a radial shock wave, which spreads out concentrically from the unit.

The principles of basic physics suggest that as the distance from a radial shock wave source increases, the energy of the wave drops dramatically. In other words, radial shock waves would logically appear to be less effective in the treatment of deeper tissues. However, because the majority of orthopedic injuries in the horse are relatively close to the skin surface, many believe that radial shock wave therapy delivers sufficient energy to cause the desired effect. Because no research information is available to directly compare the effects of radial shock waves to focused shock waves, veterinarians are relying largely on anecdotal reports of treatment successes and failures.

Use In Human Medicine

For the past 15 years, ESWT has been used successfully in human medicine as a non-invasive technique to break down kidney stones. Similarly, ESWT has been used successfully to break down gallstones and sialoliths (stones in the salivary glands). Recently, encouraging research results have been made available concerning treatment of people who suffer from chronic pain attributed to "tennis elbow" (lateral epicondylitis), "heel spurs" (plantar fasciitis), and other conditions.

In one study using radial shock waves on 103 human patients (48 with placebo treatment), 48% of people suffering from chronic (long-term) heel spurs were able to return to full function in their sports activities three months after their final treatment. In another study (also using radial ESWT) involving 116 patients (61 with placebo treatment), 37% of people suffering from chronic pain due to tennis elbow were treated with ESWT, and were able to regain unlimited sport activity three months after the final treatment.

The study also determined that 73% of the treated patients were complaint-free in every-day life. The studies found that the initial improvement was slow, yet vast improvement was felt four weeks after final treatment.

Use In Veterinary Research

ESWT also increases bone formation. Scott McClure, DVM, PhD, assistant professor specializing in equine surgery at Iowa State University, studied the effect focused ESWT had on the cannon bones of four horses, and presented the results at the 2000 American Association of Equine Practitioners convention. McClure observed a number of significant points: 1) No significant lesions were identified grossly or histologically (in tissue sample examination) in the skin or other soft tissue structures after treatment; 2) Sub-periosteal and endosteal (outer and inner bone surface) hemorrhage was seen near the point of application; 3) No microfractures were detected. Additionally, these horses did not appear to experience significant negative side effects.

Another presentation at the 2000 AAEP convention described ESWT used to treat horses with chronic lower hock joint (tarsometatarsal and distal intertarsal) disease. In that study, 74 horses with lameness due to lower hock joint disease were evaluated. Those horses were either poorly responsive or had declining response to traditional treatments. Focused ESWT was administered to the horses under general anesthesia.

At the 90-day follow-up examination, 80% of the horses had improved at least one grade of lameness. A decrease of two degrees of lameness was seen in 42% of the horses, and 18% of the horses were completely sound. No horses worsened following ESWT treatment, but 20% of the horses did not improve following one treatment.

The researchers noted that the treatments did not cause consistent radiographic (X ray) changes. Additionally, ESWT did not appear to accelerate fusion of the lower joints of the hock. The researchers concluded that ESWT should be considered as a viable non-invasive mechanism to treat bone spavin (lower hock joint disease) in the horse.

Another study presented at the AAEP convention evaluated radial ESWT for treatment of 30 horses with lameness attributed to chronic refractory high suspensory disease. K. Josef Boening, DMV, of the Tierärztliche Klinik Telgte in Germany presented the study. Horses were treated a maximum of three times at two- to four-week intervals.

At the first follow-up examination (four weeks after the last treatment), 16 horses were completely sound and nine others showed a distinct reduction in lameness. Five horses showed no reduction in pain. Six months after the final treatment, 18 horses had returned to full work, and three horses showed no improvement. Chronic high suspensory disease can be frustrating to treat for the veterinarian and horse owner because of high recurrence rates and/or poor response to therapy. Therefore, the results of this study are highly favorable for the treatment of this particular problem. The researchers concluded that ESWT is "an excellent non-invasive alternative therapy for this condition."

From this brief summary of recent scientific literature, focused and radial ESWT appear to show great promise for reducing lameness from various orthopedic injuries.

The University of California, Davis, has used ESWT for approximately 18 months at the time of this writing. Jack Snyder, DVM, PhD, Dipl. ACVS, Head Surgeon at the University of California, Davis, has used ESWT on approximately 200 equine patients. Snyder primarily uses a focused extracorporeal shock wave machine and is convinced that ESWT is an effective method of stimulating bone healing. Additionally, Snyder has found that the focused extracorporeal shock wave can stimulate healing of certain soft tissue structures (suspensory ligaments). He is uncertain about the efficacy of ESWT for treatment of osteoarthritis.

Radial ESWT In Private Practice

In addition to the discussed literature, we have made the following selective observations of ESWT effects at the Furlong and Associates Equine Veterinary Practice in Oldwick, N.J., over the past year. Furlong and Associates was founded by Brendan W. Furlong, MVB, MRCVS, who has been a practicing equine vet for 25 years. Additionally, Furlong has served as a United States Equestrian Team vet for over 15 years. Under his watch, U.S. riders and drivers have won seven medals in Olympic, Pan-American, and World Championship competitions. Currently there are seven vet associates with this full-service, cutting-edge equine practice.

We used the DolorClast portable ESWT unit, which delivers a radial shock wave. At the time of this writing, 235 treatments had been administered to approximately 90 horses at our practice.

Once an accurate diagnosis is made, the treatment protocol recommends a series of two to three treatments, with most treatments being 10 to 14 days apart. During each session, the horse is sedated and the affected area is clipped and cleaned. A twitch is applied to the horse and in the case of a radial unit, the handpiece is applied directly to the affected area. Two thousand shock waves are delivered over approximately five to 10 minutes. Following treatment, some horses experience swelling and sensitivity at the treatment site for a maximum of 48 hours. The majority of horses showed no signs of discomfort or edema (swelling) following treatment.

In general, there has been very favorable feedback from horse owners, trainers, and other veterinarians regarding the results of ESWT treatment. Because the technique is non-invasive and the system involves only manual restraint with sedation, there is little associated risk to the horse. However, treatments can be temporarily painful to the patient, particularly when treating areas with little soft tissue between the skin and underlying bone. In some cases, horses were locally anesthetized in order to ensure safe and effective treatment or to avoid discomfort for the patient.

When evaluating the response to treatment, it is hard to determine whether the reduction in lameness is due to the analgesic effect derived from the treatment, or the presumed induction of tissue remodeling. This question becomes particularly relevant when deciding when a horse should return to full work.

The analgesic effect might make the horse sound, but the tissue might not be fully repaired, in which case one must proceed cautiously in order to avoid a potentially catastrophic breakdown injury. This is an important consideration when using this treatment--veterinarians, owners, and trainers need to be aware of the transient analgesic effects of ESWT.

Over the past year, our practice has treated 25 horses with radial ESWT for high suspensory disease. Of those 25 horses, 22 showed a reduction in pain, 16 successfully returned to full function, and three horses showed no improvement at all. These findings are comparable to those described in the study by Boening. In comparison to non-treated sport horses with high suspensory injuries in this practice, these results are quite favorable.

Navicular Treatment?

At this time, no results have been published regarding the treatment of navicular-related injuries, and response to treatment with ESWT has been inconsistent. Some horses have responded dramatically, and others have shown minimal improvement. The variable response might be attributed to the myriad of soft tissue and bony etiologies (causes) of heel pain in the horse. Three horses in our practice with deep digital flexor tendon insertionopathies (injuries where the tendon attaches to the coffin bone, diagnosis confirmed with nerve blocks and bone scan) did not respond to treatment. One horse with a large bone cyst on the navicular bone also did not respond to ESWT.

However, horses with classic navicular syndrome often improve one to two lameness grades one month after the final treatment. For that reason, I conducted a bone scan prior to radial ESWT treatment on a 1,000-pound Thoroughbred with chronic navicular bone fracture (over one year in duration) and advanced osteoarthritis of the coffin and pastern joints. The horse was treated three times at 14-day intervals with a follow-up bone scan nine weeks after the first treatment. The reduction in radioisotope uptake (a barometer of bone remodeling) correlated with a marked reduction in lameness, which improved by two grades (see images page 60).

Splint Treatment?

Treatment of active splints and other exostoses (bony growths) frequently results in immediate improvement in lameness. Eventually, the injured structures tend to decrease in size. Similarly, treating insertional injuries of the distal sesamoidean ligaments in the palmar/plantar pastern area has yielded encouraging results.

A 2-year-old warmblood colt with chronic forelimb lameness (of four months' duration varying from grade II to grade IV) was found (via bone scan) to have severe increased radiopharmaceutical uptake in the shoulder blade, just above the shoulder joint. Immediately following the first radial ESWT treatment, his lameness improved noticeably. Upon evaluation before the second ESWT treatment, the colt was sound. A third treatment was administered, and the patient was still sound nine months later.

We saw variable response to treatment of two Thoroughbred horses with sesamoid bone fractures. In the first horse (a 3-year-old racehorse), which had a displaced apical fracture, minimal response was noted following three treatments. In the second horse (a 4-year-old racehorse), which had a midbody non-displaced sesamoid fracture, a seemingly dramatic response resulted. The horse was first treated 30 days post-injury, with three treatments administered over a six-week period. Follow-up examination 12 weeks post-injury revealed no abnormalities in radiology or scintigraphy. The horse raced successfully 6 1/2 months post-injury and was sound after two races.

Extracorporeal shock wave therapy is a new and exciting treatment modality offered for treatment of characteristically slow-healing, frustrating orthopedic injuries in the horse. However, ESWT is not appropriate therapy for every case. As we gain more experience with it, veterinarians will be able to specify unique treatment protocols for each injury. Clearly, more research is needed in order to better understand which injuries respond to treatment and what the long-term prognosis is following such treatments.

Editor's Note: Furlong & Associates can be reached at 101 Homestead Rd, Oldwick, NJ 08858; 908/439-2821.

Find Out More About ESWT

For more information about extra-corporeal shock wave therapy (ESWT) treatments and equipment, contact:

EMS Medical America

12092 Forestgate Drive, Dallas, Texas 75243
800/367-0367; fax 972/690-8981

Focus-It, Shared Services for Shock Wave Therapy
245 Sea Holly Circle, Roswell, Ga. 30076
770/587-1055, fax 781/623-5807

Storz Medical (supplier to Focus-It, U.S.)
Unterseestrasse 47, CH-8280 Kreuzlingen
+41 71 6774545; fax +41 71 6774505

Shock Waves Inc. (Equitripsy)
75 Wade Green Business Center, Suite 610
1301 Shiloh Road, Kennesaw, Ga. 30144-7154;
770/642-9769; fax: 770/642-6307

About the Author

Mark Revenaugh, DVM

Mark Revenaugh, DVM, is an Illinois native who has worked with and ridden horses all of his life. Graduating from the University of Illinois College of Veterinary Medicine in 1991, he now operates a unique, "leading-edge" equine practice that focuses exclusively on lameness and performance issues with a full range of diagnostic and therapeutic options. Since 1997, Dr. Revenaugh has worked as a veterinarian for the United States Equestrian Team and has been Official Team Veterinarian at numerous competitions. He is also on the USEF vet panel. His credentials also include accreditation in the FEI (Federation Equestre Internationale).

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