Shock Wave Therapy

The general consensus question at the 2003 AAEP Convention's shock wave therapy table topic was, "How can I make this technology work for my patients?" Scott Swerdlin, DVM, MRCVS, of Palm Beach Equine Clinic in Florida, and Scott McClure, DVM, PhD, Dipl. ACVS, of Iowa State University's College of Veterinary Medicine, were facilitators. Both have significant experience in using shock wave therapy (SWT) in sport horses.

SWT has been shown to have a significant analgesic effect and therefore is not currently used prior to racing or in sports overseen by the Federation Equestre Internationale (FEI).

While scientists aren't sure what it is about the pressure waves that stimulates healing, McClure said, "Historically, we can see some neovascularization (new blood supply generated to the damaged areas). There is something happening at the cellular level, and it's dose-dependent."

Swerdlin said, "It stimulates fibroblast activity, which causes more rapid healing. The pattern of healing seems to be more in linear fashion for tendons and suspensories, so that makes for a more successful regime as far as response to treatment."

McClure and Swerdlin listed the places where SWT has been found to be useful:

  • High suspensory injury--the results are lesion-dependent and take patience and time. Swerdlin recommends a lay-up time of at least eight months for recurrent proximal suspensory ligament injuries. "In my opinion, those horses not given sufficient time prior to re-entering competition may re-injure the proximal suspensory."
  • Proximal suspensory disease.
  • Distal branch suspensory injuries--"You can see remarkable results," said Swerdlin.
  • Navicular disease (see below).
  • Tendon applications (see below).
  • Back problems--Horses treated for back pain with SWT have done well and come back to work more quickly. Swerdlin believes that SWT has some value in giving muscle relaxation to horses with back spasms.
  • Hock injuries.
  • Pasterns--"I'll treat to help a horse along a bit. It's a chronic degenerative disease. We're not going to make them new," said McClure.
  • Osteochondrosis lesions.
  • Subchondral bone cysts.
  • Sesamoiditis--Seems to respond well to SWT, probably due to the large number of vascular channels.

There was discussion on treating navicular injuries and deep digital flexor tendon (DDFT) attachments. The navicular area can be treated through the heel bulbs and through the frog.

It's important the hoof be soaked before treatment to soften the area so that shock waves can pass through more easily. McClure feels he gets the best results using a series of two to three treatments on navicular problems, whether they are at short increments (three times a week) or up to six-week intervals.

Swerdlin pointed out, "Some horses might look worse directly after navicular treatment, but improve after 72 hours. It's important to tell the client that."

Swerdlin and McClure agree that they've seen improvement of at least one grade of lameness in 60% of the horses treated for navicular problems. "They will go for a show season or two following treatment. It's not for every horse," said McClure.

SWT How-To

McClure and Swerdlin said the companies selling SWT units often provide training to the purchasers, but they provided a few take-home tips for veterinarians:

  • Ossifications in a ligament will not go away. "We're not doing lithotripsy," said McClure. (SWT for horses was adapted from lithotripsy, a type of shock wave therapy used in humans to break up kidney stones.)
  • Shock waves should be run at lower energies for acute injuries than for chronic ones.
  • A three-dimensional treatment of as much of the injured area as possible is desired;
  • The majority of horses will improve, some will not.

Neither McClure or Swerdlin could recall an instance when a horse became worse because of SWT, but if not used wisely, the treatment could cause damage. They advised against treating sites of sepsis (infection). It has been shown that tumor cells can be shaken free with shock wave therapy, and the same might happen with bacteria. "Anytime you use too much energy and too many pulses, you can create a problem," said McClure. (For more on safety of SWT, see article #4974 online.)

Treating acute cannon and splint bones injuries works very well, as long as the horse isn't exercising (again, because of the analgesia, re-injury could occur). (See article #4985 online.)

Conformation & Racing Problems


According to two recent studies completed at Colorado State University (CSU), racehorses with specific conformation are more likely to have certain musculoskeletal injuries. C. Wayne McIlwraith, BVSc, PhD, DSc, FRCVS, DrMedVet (hc), Dipl. ACVS, director of CSU's Gail Holmes Equine Orthopaedic Research Center, presented results from the studies in which objective measuring was used to determine which limb conformations predispose the racing Thoroughbred and Quarter Horse to musculoskeletal injuries ranging from minor to catastrophic.

Tina Anderson (who worked on this project for her PhD) and McIlwraith developed a novel way to objectively determine what to look for structurally in racehorses that might predispose them to injury.

In the first portion of the study, 115 3-year-old Thoroughbreds (all bred and raised at one farm) were photographed from the front, rear, and side with special markers placed in specific places. All photographs included a ruler to ensure correct scale. McIlwraith and others measured lengths and angles of conformation with a software program, and they used an objective method of grading the degree of offset knees (bench knees).

McIlwraith and colleagues then recorded clinical observations, clinical conditions (including diagnoses from the radiographs), and made subjective evaluations of limb rotation in each horse. These parameters were collected every two months from birth to cessation of the study.

Fetlock problems largely were attributed to offset knees, implying changes of stress in the fetlock joint in horses with this conformation. The most common finding was effusion (swelling) of the front fetlock joints (28% right, 31% left), which wasn't surprising since inflammation, synovial effusion, and varying degrees of lameness are often seen in horses in training.

In looking at carpal angle (how straight the leg is when viewed from the front), the researchers found that as the angle increased (foot farther out to the side rather than straight under the knee), carpal (knee) effusion and fractures decreased.

"A straight leg would be 180 degrees," explained McIlwraith. "As we saw it become more valgus (foot moving out from the midline), we saw an increase in the carpal angle. The odds of injury were down by a factor of 0.68 for every one degree increase in carpal angle."

This is important to Thoroughbred owners because buyers generally seek a straight leg, and often owners request surgical manipulation of a horse with carpal valgus to make the forelimb straighter. "By having a really straight leg, we may be increasing carpal problems," he explained.

Researchers also found that long toes were associated with knee problems, and that having a longer scapula (shoulder blade) decreased the likelihood for forelimb fractures.

Quarter Horse Study

The second study was completed using 160 2-year-old Quarter Horses in training at Los Alamitos Race Course in California. The project again involved Anderson and also Nancy Goodman, DVM, and Ricky Overly, DVM, at Los Alamitos. All of the animals were unraced and had no known racing injury or lameness. McIlwraith and colleagues collected and analyzed the data as they did in the Thoroughbred study.

In the Quarter Horse study, it was found that the longer the humerus (the bone between the shoulder joint and the radius, which is the forelimb above the knee), the more likely a first phalanx (upper pastern bone) chip fragment would occur in the left foreleg or that the horse would develop synovitis/capsulitis in the knees. The horses were more likely to sustain carpal chip fragments as the length from their elbow to the ground increased. Also, for every degree that the shoulder was more upright, the horse was more likely to sustain coffin joint fracture, just as horses with more upright pasterns were more apt to develop capsulitis and synovitis. Finally, just as in the Thoroughbred study, offset knees increased incidence of fetlock synovitis and capsulitis. (See article #4986 online.)

Triage of Acute Racing Injuries


Severe injury of a racehorse is one of the most visible and critical situations race track practitioners must handle. Mary Scollay, DVM, senior association veterinarian for Gulfstream Park and Calder Racecourse, and Celeste Kunz, VMD, chief examining veterinarian of the New York Racing Association, moderated a Sunrise Session on triage of acute racing injuries.

"The emergency treatment of catastrophic injuries on the racetrack can influence or even determine their prognosis," stated a paper handed out by Kunz during the session. However, "While injury management guidelines exist in the AAEP Guide to Racetrack Practice, there are not really established protocols for much of the stuff we do out on the track in emergency situations," said Scollay. "There can't be one simple protocol because each situation is different. If you have a checklist-type approach, you will get it wrong."

The down horse isn't always a down horse, said Scollay. Sometimes he might hit the ground hard and be stunned, but not severely injured.


There are many types of fractures and various ways of handling them. Much time was spent discussing splint options, compression boots, splint padding, etc.

"Your job as the veterinarian at the scene is to assess, report, and restrain the horse," Scollay said. "How you stabilize that horse also depends on where he's going--there's a way to prep a horse for transport to the nearest hospital, and a different way to ship him several states over to a specialty hospital."

There was some discussion of stabilizing hind limb injuries, as they are much more difficult than injuries to forelimbs. "You see more P1 (long pastern bone) fractures in the hinds than in the fronts," Kunz said. But these aren't the only injuries a track veterinarian might see in the hind leg. "I watched one horse who had a complete fracture of the tibia continue to run three-legged," related Kunz. "Not only can they walk three-legged, they can run! But that horse calmed down a lot once his leg was splinted and stabilized, even without sedation. David Nunamaker (VMD, Dipl. ACVS, Jacques Jenny Orthopedic Research Chair at the University of Pennsylvania's New Bolton Center) has been using an air compression boot that you pump up to stabilize lower leg fractures."

Scollay added, "Stabilizing bad lower fractures can help stop the horse from trying to 'shake off the foot.' Don't feel like if you don't have all the expensive toys that you can't do this. PVC makes a wonderful stabilizer. And it's essential to have attending veterinarians on the grounds when their clients' horses are running," she asserted. "You can do the best triage in the world, but if no one's there to get the horse, then it's not good for him."

Kunz noted that apprentice riders might inadvertently worsen injuries by not recognizing them as quickly as more experienced riders. Also, while treating the injury is the veterinarian's responsibility, the jockey is "first on the scene" and will often play a role in the severity of the injury.

When to Pull the Horse?

The best way to avoid injury is time spent on pre-race inspections. This can be a difficult and thankless part of the job.

"Any groom can make a horse lame," said Scollay. "Especially a lame groom! A horse also can look lame when restrained by the pony. If the jockey says he feels something's 'off,' give the horse a chance to warm up away from the pony and then evaluate the horse."

This touched off a discussion on how a veterinarian works with a jockey to handle a possible unsoundness issue, with some instances where a jockey might want to call a horse unsound rather than ride it for whatever reason. "If the horse is older and moves funny all the time, that's the trainer's issue," Scollay said. "But I won't say the horse is lame if I don't see it.

"But there's also things the jockey might be able to feel that I can't see," she stated. "I have made it clear to riders that they have to tell me if they feel something subtle."

When the horse has trouble in the gate, both veterinarians recommended backing the horse out (if he isn't caught), checking him over, and giving him a few minutes to "reset," jog, and re-enter the gate if he's not hurt so he doesn't run his race in the gate.

"If it's not an injury situation, the stewards make the call," Scollay said.


Risk and liability are big concerns in racing, particularly in very visible situations with thousands of spectators. Some attendees strongly recommended that track veterinarians keep their own malpractice insurance in addition to the track's policy.

"As soon as the horse is off the track, it's the attending veterinarian's responsibility," said Scollay. During emergency treatment/stabilization, she said, the veterinarian is responsible for anyone getting hurt. "The horse's value might be high, but it's set. There is an increased risk of human injury when working with an injured horse and as the veterinarian on scene, I may not have the opportunity to choose who will be assisting me in these situations. You may be training people while you are addressing the needs of the horse," she said.


"When I have an overheated horse, I'll usually check on him the next day and talk to the trainer about prevention (i.e., running the horse at night or in cooler regions), but keep him off the vet's unsoundness list," Scollay said.

Kunz described light-weight sheets commonly used to treat burn victims that she has used with great success in overheated horses. "Often the horse looks crampy first, kicking out a bit. You put these sheets in cold water, then on the horse. They work really quickly and stay cold for a long time." (See article #4984 online.)

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