Extracorporeal Shock Wave Therapy (ESWT)

Extracorporeal Shock Wave Therapy (ESWT) is a new technology using shockwaves to treat chronic, painful conditions of the musculoskeletal system.  A shockwave is an intense, but very short energy wave traveling faster than the speed of sound.  The word “Extra-corporeal” means “outside the body” and refers to the fact that the shockwaves are generated outside the body.

What is the origin of ESWT?

The basic science behind ESWT is analogous to lithotripsy, the technology that uses acoustic shockwaves to break up kidney stones without surgery. The technique of using shockwaves to break up kidney stones has been around for a nearly a quarter century now, and in the process of treating thousands and thousands of patients, it was found that many people undergoing the procedure had other unrelated aches and pains disappear. It was at this point that scientists began to consider that shockwaves may have an effect to heal other sorts of tissues.

Specialized machines were then developed specifically with the idea of using these shockwaves on other parts of the body, and this is the origin of ESWT.

The type of shockwave therapy we use, then, is specialized to specifically help treat musculoskeletal conditions.

What conditions can you treat with ESWT?

Extracorporeal Shock Wave Therapy can be used to treat a wide variety of musculoskeletal conditions, particularly those involving where major connective tissues attach to bone.

Complaints involving attachment points for tendons and ligaments in major joints like the shoulder (such as the rotator cuff), elbow (epicondylitis or tennis elbow), hip, and knee (tendinitis or “jumper’s knee) are common sites for ESWT.

One of the areas most frequently treated with ESWT, however, is the foot. This is our specialty.Some conditions in the foot that have been treated with ESWT include:
Plantar Fasciitis or Fasciosis (Strained Arch)
Achilles Tendinitis or Tendinosis
Calcific Tendinitis or Tendinosis
Connective Tissue Pain and degeneration
Muscle Pain and Injuries
Joint Injuries
Morton’s Neuromas

And as ESWT encourages bone healing, it has been used to help treat:
Stress Fractures
Avascular Necrosis (A dead portion of bone)
Slow-healing bone (Delayed unions)
Non-healing bone (Non-unions)

There are also urological conditions that respond to ESWT, such as Peyronie’s Disease.

Research presented at the 2005 International Conference on ESWT in Vienna and the 2006 International Conference in Rio de Janeiro demonstrated that ESWT is also being studied for use for a wide variety of other conditions as disparate as skin ulcers and other chronic dermatological lesions, infections, angina, arthritis, reflex sympathetic dystrophy (RSD), and certain neurological conditions.

When is ESWT considered as a treatment for these sorts of conditions?

Shock Wave Therapy is generally considered when the following criteria are met:
When patient has a diagnosis that is considered to be responsive to ESWT.
When simpler and less expensive treatment alternatives have failed or aren’t appropriate for some reason.
When surgery or other more invasive treatments are alternatives.
When the patient fully understands the procedure.
When there are no known contraindications to the procedure.

When can’t you use ESWT?

ESWT is not typically used in the presence of bone tumours, certain metabolic bone conditions, and certain nerve or circulation disorders.  ESWT isn’t typically used in pregnant patients and locations of an open growth plate, (where the bone is still growing).  It’s not currently used in areas where an infection is present, (though there is some early research suggesting ESWT may actually help with infection).  It also shouldn’t be used in conditions or locations where gas or air is present in the body, (rare in the locations where ESWT is typically used)–or for other conditions as determined by your doctor.

Assuming you have an injury appropriate to extra-corporeal shockwave technology treatment, most recent independent studies suggest somewhere between a 65% and a 95% “success” range, with values around 80% being the most commonly cited number.  And it’s important to note that most of these studies have success rates as determined by the patient, himself, in terms of pain and function.

How fast does ESWT work?

We find that many patients get an initial degree of improvement almost immediately following treatment. This effect is usually (but not always) temporary, and is associated with an anesthesia effect from the hyperstimulation of the tissue from the ESWT.

It takes several days for injuries to begin to heal, and many patients see an improvement before the end of the second week.  Depending upon your diagnosis, the healing process may take several weeks or even months to be completed, but pain relief often precedes the completion of the healing process.

How safe is ESWT?

The basic technology involved with extracorporeal shockwave technology has been used for decades now on quite literally millions of people. The technology has been used most extensively in Europe, particularly the German-speaking countries, where this technology originates. In all its use, ESWT of the musculoskeletal system has been found to have virtually no serious side-effects.  In fact, even mild side effects like tingling, aching, redness, or bruising are relatively rare, modest and short-lived.

Further, effects like these appear to be more common with higher energy treatments, particularly those from earlier generations of ESWT technology than that which we use.  We’ll discuss more about the different ESWT technologies below.

How does ESWT work?

Simply put, extracorporeal shockwaves stimulate certain components within the body so the body is able to heal.  And ESWT is able to accomplish this even in chronic cases, when the body has demonstrated a previous unwillingness or inability to do so by itself.

In addition to stimulating the healing process, ESWT seems to have a direct effect on nerves, diminishing pain.

Many traditional therapies–such as anti-inflammatory medications, steroid injections, physiotherapy, massage, acupuncture, and so forth–can assist the body during the early, acute phase of an injury.  However, they are much less effective in assisting the body to heal when an injury becomes chronic.  As an example, many patients can relate to a history where a steroid injection (like cortisone) seemed to be effective in resolving pain early in their healing process, but subsequent injections were much less effective. This isn’t really surprising when you realize that a chronic-state, degenerative injury isn’t likely to respond well to a medication designed to affect an acute-phase, inflammatory condition.

What makes ESWT unique is that it is one of the very few technologies in any field of medicine that seems to work best when an injury reaches the chronic, non-healing state.  ESWT appears to be able to jump start the healing process in chronic, non-healing injuries and move them back into the acute phase of healing.

Medicinal effects:

First, this shockwave exerts a mechanical pressure and tension force on the afflicted tissue.  This has been shown to create an increase in cell membrane permeability, thereby increasing microscopic circulation (right) to the tissues and the metabolism within the treated tissues, both of which promote healing and subsequent dissolution of pathological calcific deposits.

Second, the ESWT shock waves pressure front creates behind it what are known as “cavitation bubbles”.  An example of a single cavitation bubble is pictured to the right.

Cavitation bubbles are simply small empty cavities created behind an energy front.  They tend to expand to a maximum size, then collapse, much like a bubble popping.

As these bubbles burst, a resultant force is created.  In the human body, this force is strong enough to help break down pathological deposits of calcification in soft tissues.

Third, as cavitation bubbles collapse, they create smaller, secondary energy waves known as microjets.  You can see how a microjet forms in the diagram to the right, and you can see it pictured in the center of the cavitation bubble in the photograph immediately above.

These microjets also create a lot of force that also breaks down pathological deposits of calcification in the soft tissues through direct, mechanical means.

In the application of an ESWT treatment in a medical setting, however, it’s not just one cavitation bubble or just a few cavitation bubbles being produced, but hundreds and thousands.

To the right you can see what hundreds of cavitation bubbles formed from a single shockwave looks like.

Multiply this by several thousand shockwaves being administered to an injured tissue through a course of ESWT treatment and you can imagine the forces that can be mustered to break down deposits of calcification that are found in joints, soft tissues and spurs.

Beyond breaking down pathological calcification deposits, ESWT has been shown to stimulate cells in the body known as osteoblasts.  These bone cells, (pictured to the right), are responsible for bone healing and new bone production, so stimulating them obviously enhances the healing process of bone.

ESWT shockwaves have also been shown to stimulate fibroblasts, (pictured to the right).  Fibroblasts are the cells responsible for the healing of connective tissues such as tendon, ligaments, and fasica.

ESWT also diminishes pain.  It does so in two ways.  First, as mentioned above, ESWT initially diminishes pain through what is known as hyperstimulation anesthesia.  This is where the nerves sending signals of pain to the brain are stimulated so much that their activity diminishes, thereby decreasing or eliminating pain. This effect is usually, (but not always), short lived.

ESWT is also believed to diminish pain over longer periods of time through the stimulation of what is known as the “gate-control” mechanism, where nerves can be stimulated to “close the gate” to pain impulses sent to the brain.  It is sometimes thought of as activating a sort of “reset” button that recalibrates pain perception.

Interestingly, and in apparent support of this theory, it was demonstrated by research presented at the 2005 conference in Vienna that using anesthesia with ESWT alters the sensor input – motor output balance of nerve fibres, inhibiting the pain-killing effect of ESWT.

In other words, ESWT appears to be most helpful for patients who are not anesthetized.   (This explains why some early studies where anesthesia was used before the administration of extracorporeal shockwave therapy did not get results as good as what is found in patients where no anesthesia is used.)

As the piezoelectric version of shockwave we use does not require anesthesia, this serves as one explanation as to why piezoelectric shockwave works so well.

While ESWT is used on a wide variety of body tissues and medical conditions (see “What conditions can you treat with ESWT?” section above), the effects of shockwaves are best documented in areas of changes in tissue density, such as where tendon attaches to bone (enthesiopathies) and where bone attaches to ligaments (desmopathies).  For this reason, it is very effective for painful connective tissue pain in such locations as the foot, knee, hip, elbow, and shoulder.