Extracorporeal Shockwave Therapy

Precision Energy. Targeted Healing. Proven Results.

Extracorporeal Shockwave Therapy (ESWT) is a non-invasive treatment that uses high-energy sound (acoustic) waves to promote healing and reduce pain in various musculoskeletal conditions. It is particularly effective for patients suffering from chronic pain in areas such as the shoulders, elbows, neck, back, knees, hips, and feet, including conditions like rotator cuff tendinitis, tennis elbow (lateral epicondylitis) and golfer’s elbow (medial epicondylitis), patellar tendinitis, greater trochanteric tendinopathy, Achilles tendinopathy, plantar fasciitis, and painful trigger points or myofascial adhesions found throughout the body.

During an ESWT session, a specialized device delivers targeted shockwaves to the affected area, stimulating circulation, breaking down scar tissue, and encouraging the regeneration of damaged tissues. The shockwaves help to activate the body’s natural healing processes, reduce inflammation, and relieve pain, all without the need for surgery or long recovery periods.

ESWT has a high success rate in reducing pain and improving mobility, allowing patients to return to their daily activities faster and with long-lasting results. The procedure is typically quick, with most sessions lasting around 10 to 15 minutes, and patients can usually resume normal activities immediately after treatment.  Most patients require 4 to 6 visits to achieve relief, with more chronic and severe cases requiring further treatment.

As a safe, effective alternative to invasive procedures, ESWT offers patients an opportunity for recovery with minimal risk and downtime!

How Extracorporeal Shockwave Therapy (ESWT) Works:

ESWT is the therapeutic use of powerful, deep-penetrating sound (acoustic) waves.  This treatment utilizes the same technology used in hospital systems worldwide to resolve kidney and gall stones in a process known as lithotripsy, including in the United States where the technology is FDA approved for this purpose.  Shockwave therapy has been used in Europe for decades to treat a variety of painful orthopedic conditions.  These waves allow for the breaking apart of soft tissue calcifications and dysfunctions in the tendons, ligaments, muscles and joints of the body.  In our clinic, we use shockwave devices manufactured by Storz Medical in Switzerland, widely considered to be the global “gold standard” in shockwave technology.  

Mechanistically, the acoustic waves produced by the ESWT device create healing in the body via a process known as mechanotransduction.  The acoustic waves create a rapid change in pressure at the tissue-level.  This mechanical energy is oftentimes sufficient to break apart painful calcium deposits and dysfunctional tissue, all while leaving healthy tissue unharmed.  This mechanical stimulus is also transformed into cellular and biological activity by stimulating mechano-sensitive cells such as fibroblasts, stem cells and osteocytes.  When molecular pathways in these cells are activated, angiogenesis, tissue remodeling, and long-term healing and regeneration will follow, as well as a decrease in inflammation and pain.  In essence, the ESWT device harnesses the human body’s natural repair mechanisms to fix damaged tissue.

Difference Between Radial and Focused ESWT:

Radial and focused shockwaves have different physical properties, modes of generation, tissue penetration depth, and also standard parameters used such as pressure amplitude, pulse duration, and impact.

Radial pressure waves are often referred to as radial shockwaves, although this is not the correct term as used in physics.  A pressure wave is a sound wave that causes fluctuations in pressure within a medium.  Radial shockwaves are produced by a pneumatic system.  With the use of compressed air, a projectile is accelerated and then rapidly decelerated by the transmitter, which is applied to the treated area.  The kinetic energy is then transmitted to the tissue in the form of radial waves, which lose power as they travel deeper into the body.  These waves have overall low energy density and slow impulse.  This treatment is mostly appropriate for larger treatment areas that tend to be more superficial, as treatment depth is 3-4 cm.  Conditions that benefit from radial shockwave include plantar fasciitis, tennis elbow, Achilles tendinopathy, and any superficial adhesions and trigger points in the musculoskeletal system.

Focused shockwaves can be generated by several means, including electrohydraulic, piezoelectric or electromagnetic shock wave generators.  In our clinic, we use the electromagnetic approach, where shockwaves are generated electromagnetically through a cylindrical coil creating opposing magnetic fields when current is applied.  Focused shockwaves, in contrast to radial shockwaves, are true shockwaves and not pressure waves.  Focused shockwaves are very high-pressure sound waves that create a sudden and significant change in pressure.  Most people are familiar with shock waves that occur when a supersonic aircraft breaks the sound barrier or when there is an explosive event like a detonation or lightning strike, and these events are known for transmitting energy from the point or generation to a remote region such as when window panes shatter.  Compared to radial shockwaves, focused shockwaves allow for greater accuracy and treatment depth.  Electromagnetically-generated focused shockwaves have a smaller focal point that allows for precise energy delivery to the desired area with minimal overall pain.  Focused shockwaves also have superior treatment depth, up to 12 cm!  This arrangement allows for better penetration into deeper tissues, and for all of the shockwave power to be applied at the required depth.  Stand off applicators can be used to alter the depth of energy delivery.  The amount of energy dispersed is minimal at the site of actual wave generation, so there is minimal damage to the skin and underlying soft tissues.  In contrast to radial shockwaves, focused shockwaves offer high energy density and fast impulse.  Focused shockwaves are optimal when targeting deep tissues such as tissue close to bone, calcifications, or delayed unions and non unions.  Additionally, patients unable to tolerate radial shockwave treatment for acute injuries due to acute pain can find focused shockwave therapy more tolerable.

Both forms of ESWT, radial and focused, increase the cell wall permeability, stimulate microcirculation and vasodilation, and release the substance P neurotransmitter responsible for pain modulation.  The focused shockwaves offer extra cavitation release of nitric oxide, causing increased cellular metabolism, neoangiogenesis (new blood vessel formation), tissue regeneration, and stimulation of growth factors.  Focused shockwaves have also been found to aid in stem cell proliferation and produce potent anti-inflammatory effects.  

Both forms of ESWT rely on continuous patient feedback during treatment to confirm delivery of shockwaves to the source of pain.  A combination of focused and radial shockwaves has also proven to be optimally effective for many conditions, and ESWT can work well in conjunction with therapeutic exercises and stretches.

Focused Extracorporeal Shockwave Therapy (ESWT)

Differences Between Ultrasound and Focused ESWT: 

ESWT has several major differences when compared with ultrasound.  Shockwaves have substantially higher pressure amplitudes.  Further, most ultrasound waves are high-frequency (several MHz) periodic oscillations with a narrow bandwidth.  Conversely, shock waves are characterized by a single, mostly positive pressure pulse followed by a comparatively small tensile wave component (a negative pressure pulse).  The effect of focused shockwaves is determined by, among other factors, a forward-directed force effect (in the direction of shockwave propagation) that causes momentum transfer to the tissue interface.  This force effect can be increased to such an extent that kidney stones can even be destroyed.  

Propagation of Focused Shockwaves:

As shockwaves are acoustic waves, they require a medium such as water or air for propagation.  Medically-used shockwaves are generated by the instrument and then transmitted to the biological tissue.  A coupling water-based gel is applied between the instrument and biological tissue to eliminate any trapped air, which could potentially significantly diminish the effectiveness of shockwaves.  Because tissue consists mostly of water and thus has very similar sound transmission properties as water, shockwaves are easily transmitted to the biological tissue.  Acoustic interfaces exist when acoustic properties (e.g., density) change.  At these locations, many phenomena familiar from the field of optics can occur such as reflection, refraction, scatter and diffraction, causing the shockwaves to deviate from a straight line of propagation.  While the various soft tissues (skin, fat, muscles, tendons, etc.) have inhomogeneous acoustic properties and thus present acoustic interfaces, the differences in acoustic properties are rather small and so propagation should be minimally impacted.

Focused Shockwave Parameters:

Medically-used focused shockwaves typically have a peak pressure of 10-100 megapascals (MPa), which is equivalent to 100-1000 times Earth’s atmospheric pressure.  Rise times (defined as the time it takes for the shockwaves to increase from 10% to 90% of its maximum pressure) are very brief at around 10-100 nanoseconds.  The pulse duration is approximately 1 microsecond, much shorter than that of medically-used radial pressure waves.

Focused Shockwave Energy and Momentum:

Shockwave energy and energy flux density are key parameters in medical applications.  Shockwaves can only have an effect on tissue when certain energy thresholds are exceeded.  The energy delivered is proportional to the utilized pressure squared integrated over time.  Energy flux density is a measure of the energy concentration delivered and is equal to the total shockwave energy delivered divided by the area over which this energy is applied.

Shockwaves also possess momentum, which is proportional to the utilized pressure integrated over time.  The momentum of shockwaves is the means by which forces are exerted upon the biological tissue.  If a shockwave is propagated in biological tissue, wave interference will be minimal if it does not strike tissue interfaces that feature abrupt changes in acoustic impedance (e.g., tissue density).  At such interfaces, wave momentum is divided into two components: one component passes right through the interface, and the other component is reflected back from it.  At harder interfaces like stones, a greater degree of the wave is reflected.  At softer interfaces like tendons and muscle fibers, a lesser degree of the wave is reflected.  This momentum, and its shifts at tissue interfaces, is of crucial importance for high-energy stone fragmentation and for low-energy medico-biological stimulation of healing damaged soft tissues.  This is because directly related to momentum are the forces which will be exerted at these interfaces, and can be used to fragment material amenable to breakage (e.g., calculi) and to stimulate elastic materials including soft tissues.  

Effects of Focused ESWT:

The physical and biological effects of focused shockwaves include direct effects on interfaces and indirect effects, notably cavitation.

The mechanism of action of shockwaves on contact with different tissue interfaces is the basis for various medical applications.  Shockwaves can pass through many types of tissue without causing damage, but at tissue interfaces there is a physical mechanism of momentum transfer and a resulting therapeutic release of force that may even fragment calculi.  These force effects occur at interfaces due to discontinuities in the acoustic impedance (which is a product of a medium’s density and the speed of sound in said medium), but hardly ever in homogeneous media (e.g., tissue or water).  Thus, focused shockwaves are the ideal means for creating healing effects in deep tissue without causing damage to the tissue that the waves pass on their way to the target area.  The focusing of shockwaves further allows the desired effect to be confined to the target area, so that side effects outside the treatment zone can be reduced or even completely avoided.  The forces arising at tissue interfaces during momentum transfer (by means of transmission and selective reflection) allow for slight movements of these interfaces.  This motion ensures that layers of cells are stretched and deformed, briefly becoming permeable to ions and certain molecules.  This process takes place over the physiologically-effective milliseconds, which allows for the exchange of biochemical substances through briefly opened pores in stretched membranes.  This mechanism, known as mechanotransduction, is paramount in promoting the medical effects of focused shockwaves.  This is specifically because mechanotransduction explains why several biochemical substances (e.g., nitric oxide [NO], growth factors, substance P) are released. The orthopedic outcomes that can be achieved via these effects include the destruction of structures amenable to breakage (e.g. calculi as in calcific tendonitis) and the irritation and stimulation of tissue structures with consequential tissue healing.  The full list of biological reactions that result from the shear and pressure forces from focused shockwave therapy-induced mechanotransduction is vast, and includes increase in cell permeability, stimulation of microcirculation (blood and lymph), release of substance P, reduction of non-myelinated nerve fibers, release of growth hormones (that stimulate the formation of blood vessels, epithelium, bone, collagen, etc.), stimulation of stem cells, stimulation of neurons, and release of nitric oxide (NO), which leads to vasodilation, increased metabolic activity, angiogenesis, and in general anti-inflammation.

In addition to the direct force effect of shockwaves on interfaces, focused shockwaves also promote cavitation in water and, to a certain extent, biological tissue.  After the alternating pressure/tension load of a shockwave has passed through the medium, cavitation bubbles form for about 100 microseconds.  The bubbles then violently collapse and emit secondary spherical shockwaves.  When close to tissue interfaces, these cavitation bubbles collapse asymmetrically while developing a microjet, which is directed at the tissue interface at a velocity of several hundred meters per second.  The microjets contain a high amount of energy and penetrative power, making them able to erode the hard interfaces of calculi.  Further, focused shockwaves passing through a medium can release gas dissolved in blood or tissue, a process deemed “soft cavitation” that results in bubble formation.  These bubbles form in a way that can cause micro-bleeding or membrane perforation, which per above also stimulates the healing response.  Due to the nature of focused ESWT, this phenomenon remains mostly limited to the focal treatment zone.  In general, effective communication between medical provider and patient is essential to identify the point of maximum pain.  This biofeedback method helps to localize many superficial and deep treatment points.  

Radial Extracorporeal Shockwave Therapy (ESWT)

Generation and Propagation of Radial Pressure Waves:

Radial ESWT, more appropriately referred to as radial pressure waves as these are not true shockwaves, involves the transmission of mechanical energy – in the form of an acoustic pressure wave – into the body tissue and pain region by means of specially shaped transmitters.  Ballistically-generated radial pressure waves feature much longer pulse lengths compared to focused shockwaves (0.15-1.5 m vs. 1.5 mm), which explains why focused shockwaves can be much more easily focused.  

Radial pressure waves are generated by the collision of solid bodies.  A projectile is accelerated using compressed air to a speed of several meters per second and then abruptly slowed by hitting a transmitter.  The elastically-suspended transmitter is brought into direct contact with the patient’s skin above the area to be treated, with a layer of ultrasound coupling gel between the skin and transmitter.  When the projectile strikes the transmitter, some of its kinetic energy is transmitted to the transmitter, which then performs a translational movement over a short distance (typically less than a millimeter) at a significantly slower speed (typically less than 1 meter per second) until the coupled tissue or the handpiece stops the transmitter movement.  The motion of the transmitter is transmitted to the tissue at the point of contact, from where it propagates divergently in the form of a radial pressure wave.

The duration of the pressure pulse is typically ~0.2-5 ms, which is approximately 1000-fold longer than those of focused shockwaves.  Typical peak pressures of radial pressure waves are 0.1-1 MPa, which is lower, by about 100-fold, than those of focused shockwaves.  The collision of the projectile with the transmitter also generates a higher-frequency acoustic wave; however, due to the large difference between the two acoustic impedances (metal, water), only a minimal portion (~10%) of this acoustic wave energy is transmitted to the tissue.  This energy transmitted from the high-frequency acoustic wave is significantly smaller than the energy of the low-frequency pressure pulse described above.

Pressure waves originate from the application point of the impact body and travel radially into the adjacent tissue.  The energy density of the induced pressure wave rapidly drops with increasing distance from the application point, meaning that the strongest effect is at the application point of the transmitter (i.e., at the skin surface).

Physical and Biological Effects of Pressure Waves:

Radial pressure waves generate oscillations in tissue which lead to improved microcirculation and increased metabolic activity.  Radial pressure waves are ideal for the treatment of superficial pain.  In the treatment of myofascial pain syndromes, radial pressure waves are indispensable for smoothing muscles and/or fascia before or after focused shockwave application.

Focused Shockwaves vs. Radial Pressure Waves

Similarities in the effects of focused shockwaves and radial pressure waves can be explained in terms of mechanotransduction as the underlying mechanism in both cases.  When focused shockwaves are applied, their short wavelength makes it possible for the effects of the stimulation pulse to be specifically exerted either superficially or at depth; conversely, radial pressure waves cannot be focused and can thus only achieve this effect at the surface, with the effect at depth significantly diminished.  Focused shockwaves should be used to treat local painful spots, chronic enthesopathies and deep trigger points.