In healthcare, Extracorporeal Shockwave Therapy (ESWT) has grown more and more in popularity over the last 2 decades for the treatment and management of, primarily, tendinopathies and other chronic soft tissue pains. However, when looking at the research, the science and the products that are available to us therapists, there are systems out there that are, strictly speaking, not ESWT.
Background of ESWT – from The International Society of Medical Shockwave Treatment (ISMST)
The first systematic investigations for the use of shockwaves in medicine were performed in the 1950’s. From 1968-1971, the interaction between shockwaves and biological tissue in animals was investigated in Germany where it was observed that shockwaves create low side effects on the way through muscles, fat- and connective tissue.
These investigations lead to the idea of disintegrating kidney stones with extracorporeal generated shockwaves. In 1983, the first commercial lithotripter was installed in Stuttgart/Germany, from there to today, over 3 million patients have been treated with lithotripters for the treatment of kidney and gallstones.
During this time, it was investigated for the use of ESWT to stimulate fracture healing and also on tendinous tissues. At the beginning of the 1990’s the first reports about shockwave therapy being used for tendinitis calcarea were published. Further investigations lead to successful treatments of epicondylitis and heel spur with reported success rates between 70% and 80%. All publications agree that ESWT showed high efficiency but very low complications and side effects for the treatment of tendons and other soft tissue conditions.
For more information please visit ISMST.
What is a Shockwave?
When looking to use Shockwave therapy, it is imperative that you know what a shockwave is and its’ key characteristics.
“A shock wave is a sonic pulse that has certain physical characteristics. There is a high peak pressure, sometimes more than 100 MPa(500 bar), but more often approximately 50 to 80 MPa, a fast initial rise in pressure during a period of less than 10 ns, a low tensile amplitude (up to 10 MPa), a short life cycle of approximately 10 μs, and a broad frequency spectrum, typically in the range of 16 Hz to 20 MHz.” Ogden et al., ClinOrthopRelRes 2001;(387):8-17.
A typical pressure profile of a focused shockwave used for therapeutic purposes is shown in the figure below. Ogden JA, Tóth-KischkatA, SchultheissR: Principles of ShockWave Therapy. ClinOrthopRelatRes 2001  8-17.
A general description of a shockwave;
- A single pulse with a wide frequency range (from approx. 150 kHz up to 100 MHz),
- High pressure amplitude (up to 150 MPa),
- Low tensile wave (up to -25 MPa),
- Small pulse width,
- Short rise time of up to a few hundred nanoseconds.
If you would like to know more about the principles of Shockwave, the referenced publication below (Ogden et. al. 2001) is a good read, but the following site breaks it down into more digestible terms. Read more.
Radial vs. Focused Shockwave Therapy
There are two different types of ESWT on the UK market, Radial and Focused. It is IMPERATIVE that you know the differences between the two as it will have a big impact on;
- Clinical outcomes
- Patient buy-in
- Durability and on-going costs
We have explained what a shockwave is in the above section – the below figures show you what the differences are between radial and focused shockwave.
The comparison of three different acoustic waves are below.
There are 3 different shockwave technologies which are used in practice;
For you to read further into these technologies, visit ISMST.
In contrast to focused shockwaves generators, which can produce shockwaves at least at the focal point, radial “shockwave” generators produce “ordinary” sound waves with pressures of up to 30 MPa and much longer rise times.
Ueberle, F.; Rad, A. J.; “Ballistic Pain Therapy Devices: Measurement of Pressure Pulse Parameters”; Biomed Tech, 2012; 57 (Suppl. 1), 700-703.
There are currently two different technologies producing radial “shockwaves”. Both use the ballistic principle and consist of a hand piece with a projectile which is accelerated towards an applicator. The two variants are;
- Air pressure acceleration (Pneumatic principle). Figure 1.
- Electromagnetic acceleration. Figure 2.
When looking to use ESWT, it is important to know what you are delivering to the tissues. There are clear differences between the radial and focused shockwave therapy sources and you really need to look into the science. The ISMST website is a great resource for you to use too, and when looking into shockwave research, look at what the device is delivering as well as the efficacy publications. Really question reps and clinicians alike and ask is it really producing a true shockwave?