Effect of shock waves

Shockwave therapy is a non-invasive treatment that promotes the healing of many types of musculoskeletal problems.


Definition of shock waves

Shock waves are acoustic waves with an extremely high energy peak.
Shock waves differ from ultrasonic waves by their pressure. In addition, ultrasound consists of periodic oscillations, while the shock wave is a single pulse.

The shock wave is based on the application of high-energy acoustic impulses to the body tissue concerned. Each shock wave treatment serves to increase metabolic activity in the vicinity of the pain area.

It stimulates the absorption of irritating calcium deposits in the tendons and the body’s natural healing process, thereby reducing pain.

Usually, three treatments with shock waves at intervals of one week are required to achieve a good result.
Treatment is carried out by directing the transducer of the shock wave device at the affected region.

The treatments last about 8 minutes and can be a bit uncomfortable.
But usually they are well tolerated by everyone.

Clinical indications

Over time, shock waves have become an effective and non-invasive method for the local treatment of musculoskeletal disorders, including:

  1. Tennis elbow
  2. plantar fasciitis,
  3. calcifications in the tendons of the shoulder,
  4. femoral head necrosis,
  5. incomplete union of bone fragments in fractures,
  6. pseudarthrosis,
  7. Burns – shock waves significantly reduce scar pain resulting from burns (so Cho et al. – 2016),
  8. osteomyelitis (Gollwitzer et al. – 2009),
  9. myofascial pain is used.

A recent study investigated the potential use of shock waves in periodontal disease (Prabhuji – 2014) and in accelerating callus formation in fractures.
Shock waves have been approved by the U.S. Food and Drug Administration for use in patients with plantar fasciitis and tennis elbow who did not improve after six months of conservative treatment (Ogden et al. – 2001).

The shock wave is an effective, non-invasive solution for chronic pain of the shoulder, foot, knee and elbow.

Development of the shock wave

The term “shock wave” refers to mechanical pressure pulses that propagate inside the human body like a wave. In 1980, the shock wave was used for the first time to remove kidney stones in a patient (Chaussy et al. – 1980).

Therapeutic effect of shock waves

Shock waves (unlike lithotripsy) are not used to dissolve tissue, but to achieve microscopic biologically intra- and extracellular effects that involve tissue regeneration.
The energy of the acoustic wave is directed from the place of origin, the wave generator, to the affected body area (Notarnicola – 2012).

How do shock waves and tissue interact during therapy?

This bombardment of the tissue produces a series of biological reactions resulting in neovascularization (development of new blood vessels), which in turn greatly accelerates the healing process.

High-intensity shock waves can be used to treat pseudoarthrosis, especially in the shin and femur; scientific studies show a cure rate of 72%.

Blood circulation is necessary to stimulate and maintain the process of regeneration of damaged tissue structures.

Shock waves cause a significant increase in:

  1. growth factor of the vascular endothelium (VEGF),
  2. nitrogen oxide (eNOS),
  3. Proliferating cell nuclear antigen (PCNA), which causes the proliferation of endothelial cells.

The result is neovascularization, i.e. the formation of new blood vessels and thus improved blood flow to the tissues.
The new blood vessels improve blood and oxygen supply, resulting in faster healing of tendons and bones (Notarnicola et al. – 2012).

This characteristic is peculiar only to shock waves, other devices used in physiotherapy do not have this property, which allows tissue regeneration.

Reduction of substance P

The concentration of substance P and prostaglandin E in the periosteum of the femur was measured.
In contrast to the femur of the other side, the release of substance P of the periosteum of the femur was:

  • higher during measurement 6 and 24 hours after extracorporeal shock wave application,
  • 6 weeks after therapy.

There was a close correlation between the release of substance P found here and the clinical course of the patient.
In fact, the pain may increase the day after therapy, while it decreases a few weeks after the application of shock waves to the tendons.

Dissolving chronic inflammation
Shock waves can change the local chemical environment. Chronic inflammation can damage healthy areas in the body and lead to chronic pain.
The activity of mast cells involved in inflammatory processes can be increased by sound waves.
Activation of mast cells can help restore normal healing and regenerative processes.

Nitric oxide plays a fundamental role in the mechanism of action of shock waves. This substance acts:

  • soothing
  • antiinflammatory
  • angiogenetic (promotes the formation of new blood vessels) (Loew et al. 1998).

The experimental results confirm that shock waves reduce the production of high-grade inflammatory mediators, i.e. substances that promote inflammation (matrix metalloproteases and interleukin) (Notarnicola – 2012).
The change in the concentration of the inflammatory mediators also supports the anti-inflammatory effect of this therapy.

Stimulation of collagen
The production of a sufficient amount of collagen is a necessary condition in the process of repairing tissues. The shock wave accelerates collagen production.
Shock waves can stimulate the proliferation of tenocytes (fibroblasts that produce extracellular matrix) and collagen synthesis.

Scientific studies have shown that treatment with shock waves increases the proliferation and differentiation of fibroblasts, stimulating the production gene:

  1. transforming growth factor β1 (TGF-β1),
  2. of collagen type I and III (Frairia et al. – 2012).

Bosch et al. (2007) found that glycosaminoglycan (GAGand protein synthesis have increased.

Femoral head necrosis
A scientific study compared necrotizing femoral heads treated with shock waves with necrotizing femoral heads without such treatment. The shock waves bring the following benefits:

  1. greater amount of living bone tissue,
  2. lower amount of necrotic bone tissue,
  3. increased cell concentration,
  4. Increase in cell activity, especially phagocytosis.

Dissolution of limescale deposits
Calcification is often the result of micro-injuries or other traumas to the detriment of the tendons. Shock waves shatter the existing calcifications.
The shock wave therapy begins with the decalcification of the calcium deposits and acts on the tendon.

Some time passes between therapy and changes that become apparent on the X-ray; therefore, a purely mechanical effect on the limescale deposits is unlikely.
Since the effect occurs delayed, one must assume a common mechanical and cellular effect that allows the absorption of calcium deposits (Perlick – 2003).

Release of trigger points
Trigger points are the main cause of pain on:

  • Back
  • Neck
  • Shoulder and limbs.

They occur in the form of palpable knots in tense muscle fiber bundles.
Here the sarcomeres are extremely contracted.
These sarcomeres contract so strongly that the blood supply decreases (Shah et al. – 2015).
Although the effects of shock waves are still somewhat unclear, it can be assumed that the sound energy switches off the calcium pump, which is located in the muscle tissue, and thus causes relaxation.

Studies show:

  • that shock waves have a better effect on the myofascial trigger points than the injection of anesthetic (Oh Hong et al. – 2017);
  • excellent results at the trigger points of the upper trapezius muscle (neck) – Min Ji et al. document an 85% reduction in pain after the 4th session.

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