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Photo credit: Emily Thurner Photography for Forward Equine Veterinary Services
Extracorporeal shockwave therapy (ESWT) is a common treatment modality offered by many veterinarians for treating lameness in horses. Most veterinarians use shockwave therapy in the treatment of arthritis and ligament injuries.
ESWT produces a high-energy shockwave that applies pressure to a desired tissue. This pressure triggers tissue damage, which may stimulate tissue repair and activate healing factors. [1]
Shockwave therapy is also purported to increase blood flow to the treated area, enhancing the delivery of nutrients and oxygen, which are essential for tissue repair. It is also believed to reduce pain by over-stimulating pain receptors, which can decrease their sensitivity.
Despite its widespread clinical use, there is limited scientific evidence to support the efficacy of ESWT, as there have not been large randomized controlled trials or experimental studies. [1] Further research is needed to determine the efficacy of shockwave therapy in treating various lameness conditions in horses.
Shockwave Therapy for Horses
Extracorporeal Shockwave Therapy is a non-invasive treatment used in horses to promote healing of injured soft tissue, bones, and joints. The shockwaves are waves of sound energy generated by a machine, and applied to the surface of the skin to target the underlying tissues. [1]
These shockwaves produce a focal area of high pressure in the tissue. [1] The shockwaves also trigger cavitation bubbles to form within the tissue as a result of high pressure, which then implode and produce additional energy waves. [3]
Depending on the treatment protocol, veterinarians can adjust several aspects of the shockwaves produced to maximize treatment efficacy. Adjustable features include: [1]
- Energy level
- Amount of pressure produced
- Frequency of pulses
- Duration of the pulses
- Depth of tissue penetration
Most treatment protocols advise three to six treatments at 2-3 week intervals. [4] This time period allows the body to heal the tissue damage ESWT produces. [4] ESWT requires good contact between the skin surface, so clipping the hair over the treatment area may be necessary. [4]
ESWT cannot penetrate solid structures such as the hoof wall and sole. [4] It also can only reach structures between 50 to 110 mm deep, making certain joints, such as the sacroiliac joint, inaccessible to this treatment modality. [4]
Clinical Use
The first use of shockwaves in human medicine was to treat bladder stones, utilizing the shockwaves’ capability to break up bladder stones into small fragments. [1]
Practitioners using shockwaves for this purpose noticed that bone density increased in the areas surrounding the treated area. [2] This finding led to the use of ESWT in musculoskeletal injuries.
Now, shockwaves are a common component of treatment protocols for suspensory ligament injuries and arthritis in horses. [1]
Effect on Tissues
The exact mechanism by which ESWT affects tissues is currently unknown. [1] When the shockwaves interact with tissues, the energy contained within each wave is released, causing compression and shear (tearing) forces on the surrounding tissue. [5] Some veterinarians suggest that this damage stimulates healing, resulting in improved function over time.
In bones, ESWT appears to cause local bleeding and microfractures to the bone surface, which in turn stimulates new bone formation. [1][5]
In tendons, ESWT causes similar damage to tendon cells, which can increase production of proteins and glycosaminoglycans, a critical component for tendon repair. [1][6] Studies in rats show increased production of collagen (the main component of tendons) after ESWT treatment.
In muscles, ESWT may increase the regeneration rate of muscle fibers after muscle damage. [3]
There are several studies in rabbits and rats showing that ESWT can increase angiogenesis (production of blood vessels) in injured tissues, which may lead to faster healing. [3] Some research indicates that ESWT may also have a numbing effect on nerves, reducing pain associated with lameness. [1]
Usage & Scientific Evidence
ESWT is becoming increasingly popular with veterinarians as a modality for treating lameness cases. [7] One survey-based study reported that 37% of equine veterinarians use ESWT at least once weekly. [7]
There are several potential uses of shockwave therapy in horses including: [4]
- Tendon and ligament injuries
- Stress fractures of bone
- Osteoarthritis
- Nonhealing bone fractures
- Back pain
- Navicular syndrome
However, there is currently limited scientific evidence to support the use of ESWT in horses. [2] Additionally, the optimum number of pulses, frequency of treatment, locations of treatment, and strength of pulses are currently unknown. [1][4]
More thorough research, including clinical trials, is necessary to validate the use of ESWT as a treatment modality for lameness.
Ligament Injuries
Veterinarians most commonly use ESWT for treating ligament injuries, particularly suspensory ligament desmitis (inflammation of a ligament). [1][7] 58% of surveyed veterinarians believe that ESWT is highly effective in treating ligament injuries in horses. [7]
Experimental studies with induced suspensory ligament injuries shows promising results. One study showed improved healing on ultrasound in ESWT treated injuries compared to untreated injuries. [2]
A randomized control trial also showed that a greater proportion of horses with suspensory desmitis treated with ESWT were back in full work after one year compared to horses treated with platelet-rich plasma. [2] These types of studies provide the most convincing eviden