(photo credit: Elvation/de)
Today's blog post is all about pressure! and sound...and the modality known as Shockwave! (formally known as Extracorporeal Shockwave Therapy or ESWT) If Therapeutic Ultrasound is a classical artist, then ESWT is the Rockstar of the sound modalities.
ESWT was born in the 80's and had its origin in treating kidney stones in patients by using high frequency sound waves to break apart stones to the size that they can pass without more invasive surgery. It quickly became a mainstream non invasive treatment method for uroliths and soon was investigated for its usefulness in orthopedics. Animal studies in the 80's showed that the treatment was effective in augmenting the bone-cement interface (as with cemented hip replacement systems,) in fracture healing and in treating tendinopathies, fasciopathies and soft tissue conditions.
Shockwaves are sound waves that have specific physical characteristics. They have nonlinearity, high peak pressure followed by low tensile amplitude, short rise time, and short duration (10 ms.) They have a single pulse, a wide frequency range (0-20 MHz), and a high pressure amplitude (0-120 MPa) These characteristics produce a positive and negative phase of shockwave. The positive phase produces direct mechanical forces, whereas the negative phase generates cavitation and gas bubbles that subsequently implode at high speeds, generating a second wave of shockwaves.
When compared with ultrasound waves, shockwave peak pressure is approximately 1000 times greater than the peak pressure of an ultrasound wave. Therapeutic Ultrasound has higher frequency waves that produce thermal and non thermal effects, where as ESWT waves do not generate heat.
The Mechanism of Action of ESWT is currently unknown but theoretical explanations are the following:
- promotion of neovascularization of bone-tendon junction
- stimulates proliferation of tenocytes and osteoprogenitor differentiation
- increased leukocyte infiltration
- amplify growth factor and protein synthesis to stimulate collagen synthesis and tissue remodeling
So what do we currently use ESWT for in veterinary rehab medicine?
- Upper and lower extremity tendinopathies
- Malunion and non union fracture sites
- Lumbosacral disease and other back pain in dogs
- Shoulder instability
When should we not use ESWT? It is contraindicated in the following conditions:
- Over major blood vessels and nerves
- Pacemakers or other implanted devices
- Open wounds
- Joint replacements
- Blood clotting disorders including thrombosis
- Cancerous tissues
Not sure if ESWT can help your pet's condition? Contact your veterinary rehabilitation therapist and find out if this would be a beneficial part of your pet's treatment plan!