Extracorporeal Shock Wave Therapy (ESWT): Indications and Scientific Evidence
World Small Animal Veterinary Association Congress Proceedings, 2018
Janet B. Van Dyke, DVM, DACVSMR
Canine Rehabilitation Institute, Inc., Faculty, Wellington, FL, USA

Therapeutic plans generally involve a combination of manual therapies (joint mobilizations and soft tissue mobilizations), physical modalities (laser, therapeutic ultrasound, e-stim, shockwave), and therapeutic exercises. The modalities are generally used to prepare the tissues for the manual therapies and therapeutic exercises. Physical modalities should never be the sole therapeutic method applied to any patient. Therapeutic parameters for each modality are chosen based upon the acuity of the injury, so the therapist must be well versed on the definitions of the acute, subacute, and chronic phases of healing. Extracorporeal shock wave therapy is also known as high energy focused sound wave therapy. This is a high energy pressure wave, or impulse, produced by supersonic craft, explosions, lightning, or other extreme phenomena that create sudden, huge changes in pressure. This is essentially a controlled mini-explosion creating energy that we can focus for treatment. The device has a ‘trode’ head in which a spark is generated, the energy from this spark is reflected off of a surface and then focused through the trode head’s bulb. The depth of penetration is determined by the thickness of this bulb. Shock waves are rapid, high energy sound waves characterized by an extremely rapid rise time or ‘pressure front,’ followed by a slight negative pressure dip that causes cavitation, and resulting in a clearly defined focal area in which the energy is concentrated. There are four types of shock wave devices: electrohydraulic, electromagnetic, piezoelectric, and radial pressure wave. Electrohydraulic devices have peak pressures of 70 MPa, rise times of nanoseconds, and create true shockwaves at all settings. Electromagnetic devices have a peak pressure of 20 MPa, rise times measured in microseconds, and create true shockwaves at high energy settings only. Piezo-electric devices have peak pressures of 15 MPa, rise times in microseconds, and create true shockwaves at high energy settings only. This group is used for lithotripsy. Radial pressure wave devices have a peak pressure of 0.4 MPa, rise times in milliseconds, and they do not produce a shock wave at any setting. The energy is completely dissipated at 0.5 to 1.0 cm of depth. These devices are marketed as ‘painless shock wave devices, requiring no sedation.’

Shock waves stimulate release of many cytokines including nitric oxide, VEGF, PCNA, TGF-b1, and BMP2, leading to a brief inflammatory phase, vasodilation, neovascularization, endothelial cell proliferation, tissue healing, and osteogenesis. ESWT causes decreased inflammation via downregulation of TNF-a and IL-10, increased bone and tissue healing via increased secretion of BMP2, TGF-b, VEGF, PCNA, and eNOS, and decreased bone via release of serotonin in the dorsal horn of the spinal cord, leading to descending inhibition. Additional medical effects of ESWT can be disruption of biological biofilm, resulting in a bactericidal effect, decreased cartilage degradation, and a temporary analgesic effect, lasting 3–4 days in one equine study. Studies have revealed beneficial effects of ESWT in treating delayed and non-union fractures, leading to 76% success in healing delayed unions (as compared to 79% success with reoperation). Used preemptively, a significant decrease was found in the incidence of nonunions in high risk fractures. In a fracture healing study in canine fracture gap models, the use of ESWT lead to significantly greater callus and significantly more cortical bone at 12 weeks postop. In a clinical canine study reported in VCOT in 2002, four of 6 dogs with non-union fractures were treated with ESWT. Three of the 4 treated dogs healed.

ESWT is used to treat osteoarthritis as well as fractures. A study reported in VCOT in 2005 showed a trend over the 14 weeks of treatment toward improved range of motion with no change in peak vertical force (PVF) in the treated group while the control group showed a significant loss of PVF. Another study in 2010 reported a significant increase in PVF in elbow OA patients treated with ESWT. This magnitude of change in PVF was similar to that seen in patients treated with NSAIDs. A study reported in Vet Surgery in 2012 showed a significant decrease in patellar ligament thickening at 6 and 8 weeks post-surgery in TPLO patients treated with ESWT. Cauda equina cases treated with ESWT resulted in an 87.5% positive response with a median duration of 13.6 months. A study out of Tufts University in 2015 revealed excellent short-term results in treating dogs with chronic lameness due to shoulder disease. Another study published in Vet Record in 2016 looked at ESWT and therapeutic exercise for supraspinatus tendinopathies. Eighty-five percent (85%) of these cases had good or excellent outcomes in both short-term and long-term follow up. Equine studies have shown decreased lameness and improved ROM 2 months post ESWT for carpal joint osteoarthritis.

Application of ESWT requires proper patient preparation. Sedation is recommended as the device creates noise and can cause some pain. It is recommended to shave the area and wipe with alcohol. Ultrasound gel is used as a medium to provide optimal sound wave transmission. The trode is moved around the treatment area, angling the head as needed to reach the target tissue. Generally, 500 to 1000 pulses are applied to each treatment area. The devices can generate 48- pulses per minute, so most treatments take approximately 2 minutes per site. The patient can be discharged as soon as recovered from sedation. The analgesic effect of this therapy necessitates limiting patient activity for 3 to 5 days post-treatment. NSAIDs may be used, but this may reduce the desired brief inflammatory healing effect.

Patients are reevaluated every 2 weeks and retreated as needed. Most indications get the best results with two to three treatments.


Speaker Information
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Janet B. Van Dyke, DVM, DACVSMR
Canine Rehabilitation Institute, Inc.
Wellington, FL, USA

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