Many of us have heard the term shockwave therapy, and some have used it to treat injuries in horses. But how much do we really know about the principles behind this innovative treatment?
At first glance, many people have trouble understanding how a shockwave can be therapeutic. After all, a shockwave is often destructive. An earthquake is a shockwave. A tsunami is a shockwave. But so is the ripple you see in water when you throw a rock into a pond. A shockwave is simply a pressure wave, or a high frequency sound wave. Any action that displaces the surrounding medium is a shockwave.
With that knowledge, how can shockwaves be therapeutic? Those used in veterinary medicine can be generated in three different ways: electrohydraulically, piezoelectrically, or through an electromagnetic field. The shockwaves are focused in the transducer head of the machine, and can be directed to a precise area of an injury. The shockwaves are transmitted readily from the transducer head, through ultrasound coupling gel and soft tissue, and the energy of the wave is released at a specific depth, depending on the transducer head being used.
Shockwave therapy can be involved in the healing process on many levels and has a role in a myriad of different metabolic processes important to healing. It has been shown to stimulate new bone growth in fractures, stimulate the in-growth of new blood vessels (neovascularization), increase cell permeability, and possibly stimulate fibroblast formation (the cells important in repairing tendons and ligaments). In addition, it stimulates stem cells occurring naturally in the body to migrate to the area being treated. Shockwave therapy has a potent anti-inflammatory effect, has been found to have antibacterial capabilities, and has a transient analgesic effect as well.
One of the most exciting recent findings (Moretti, et al) has been that shockwave therapy can actually interrupt the progression of arthritis and alter the process of cartilage degradation. It does this by down-regulating two mediators that play a central role in the cyclical death of chondrocytes and the breakdown of the cartilage matrix that occurs in osteoarthritis. The finding that shockwave therapy can actually reduce these mediators of chondrocyte breakdown to levels found in normal joints is a major breakthrough in the study of osteoarthritis. It means shockwave may provide a protective effect against the progression of osteoarthritis.
This therapy has been used extensively in Europe, Asia and South America to treat a wide variety of soft tissue and orthopedic injuries in people. It is the treatment of choice in many areas of the world for non-union fractures. It is also very effective at treating chronic, infected wounds that have not responded to traditional therapies, and has been approved by the U.S. Food and Drug Administration to treat tennis elbow and plantar fasciitis in people who have not responded to conventional treatment. Shockwave therapy has been used in the U.S. in veterinary medicine for approximately 12 years. It has been successfully used to treat soft tissue and bony problems, both acute and chronic, including suspensory ligament injuries, with or without avulsion fractures, tendon injuries, arthritis, collateral ligament injuries, navicular syndrome, impar ligament injuries, ringbone, joint inflammation and pain, back pain, neck pain, and muscle tears and strains. While treating suspensory injuries is one of the most common applications, shockwave therapy is also very valuable for treating injuries to soft tissue structures within the hoof when there are few other alternatives for treatment.
In terms of treating osteoarthritis, the Moretti et al study has now placed shockwave in the forefront of joint therapies for treating the early stages of degenerative joint disease, with the added benefit of being non-invasive. This means shockwave therapy may be indicated earlier in the disease timeline to protect the joint and slow the progression of osteoarthritis, leading to a more active life, better quality of life, and fewer treatments with intra-articular injections and NSAIDS. Using shockwave therapy more proactively is likely to provide benefits well beyond pain management in these cases.
The treatment protocol for shockwave therapy depends on the diagnosis of each individual patient. Treatment varies with the number of shockwaves and their energy levels. For example, in the case of an acute tendon injury, the energy and number of impulses would be reduced from those used to treat an injury that was a month old. Most conditions are treated a total of three times, spaced at two to three week intervals.
After treatment, a reduction in pain and/or swelling may occur within hours. This may last for two to four days before the animal returns to close the original status. Over the next two to three weeks, actual healing will take place. It is important to note that shockwave therapy does not necessarily speed up the healing process, but will generally lead to a higher success rate and a better end result. In competing horses, it can be an important noninvasive adjunct to help keep them comfortable. For example, it can be very useful in helping a horse with a sore back to achieve comfort and freedom.
Shockwave therapy holds potential in many different areas. Current research projects include evaluations of shockwave treatment to stimulate repair of the heart muscle after myocardial infarction; to enhance spinal fusion in rabbits; to modulate physeal (growth plate) growth; to treat osteonecrosis (bone death) of the femoral head; and to investigate its effects on bacteria and on periodontitis (inflammation of the gums). Still other studies are looking at the role of shockwave therapy in the migration and activation of stem cells, peripheral nerve repair, wound healing, and burn injuries.
In human medicine, the newest frontier in shockwave therapy is its use in wound healing and treating burn injuries. Numerous case reports have shown it can successfully treat patients with longstanding infected wounds. Many of these patients were poor surgical candidates or already had several unsuccessful surgeries aimed at treating the wound. In several cases, amputation of a limb was the next step. Shockwave therapy has successfully treated these wounds with generally no reoccurrence of the infections.
Burn injuries in horses, while thankfully relatively uncommon, can be devastating. Shockwave therapy may provide an important adjunct to the support and rehabilitation of the animal. In 2010, I published a case report in the peer-reviewed veterinary journal, Equine Veterinary Education, detailing the treatment with shockwave therapy of a horse that had suffered severe burns over more than 25% of his body. “Within 24 hours of treatment, there were new blood vessels visible at the burn edge, the smell was gone, and the pus that was oozing through the scabs was markedly reduced. In addition, the horse was significantly more comfortable.” The healing of this large thermal injury was significantly enhanced through the use of shockwave therapy, and the horse gained an excellent prognosis as a direct result.
In summary, shockwave therapy is an important component in the treatment of many musculoskeletal injuries in the horse. A significant amount of research is being conducted internationally, and as a result, new applications are being developed. It can be used for so much more than just suspensory injuries – it is a non-invasive therapy that essentially helps the body heal itself in ways we never knew of or understood before.
Not All Machines Are Created Equal
It’s very important to recognize that not all shockwave machines are created equal. Some that are marketed as shockwave machines do not generate a true shockwave. They generate what is called a ballistic or radial wave. The physics of this type of wave are completely different from that of a true shockwave. These machines look like a small jackhammer.
The problem with this type of wave is that most of the energy is deposited at skin level, and the energy drops off rapidly as you move into deeper tissues. These units can be useful for treating skin lesions or wounds, but deeper injuries are not likely to receive the energy necessary to help the healing process.
Additionally, the entire area around the treatment site receives the wave, which can potentially have harmful effects. Treatment with this type of machine is generally considerably less expensive than with a true focused shockwave, but is not comparable in terms of technology or results.
Dr. Jenny Johnson is a 1986 graduate of the University of Pennsylvania School of Veterinary Medicine, where she also completed an internship in large animal medicine and surgery. She owned a Standardbred racetrack practice in Florida and Pennsylvania for a number of years, but in the early 90’s returned to her true passion of show horses. She had a solo practice in Wellington, FL, specializing in high performance hunter, jumper and dressage horses for approximately 10 years. Now based in the Los Angeles area, Dr. Johnson owns Oakhill Shockwave and Chiropractic, a practice dedicated to helping horses achieve their highest level of comfort through innovative and noninvasive therapies. Dr. Johnson is also an active competitive showjumping rider and truly understands the physical and mental demands placed on equine athletes. equineshockwave.com