Shock Wave Therapy for Calcific Shoulder

As soon as the diagnosis of calcific shoulder is mentioned in Germany, the call for shock wave therapy is already heard. But what is this therapy actually, what different techniques are used, and what should one pay attention to?

If you want to understand shock wave therapy, you unfortunately cannot avoid some basic physical explanations. Only then can you understand the range of applications, the various devices used, and the limitations of the procedure.

The term "shock wave therapy" is historically derived from shock wave lithotripsy, which was first used clinically in 1980 for the non-contact and non-surgical fragmentation of kidney stones. Shock wave therapy is often abbreviated to ESWT. E stands for extracorporeal, which means applied outside the body, SWT shock wave therapy.

The Creation of a Shock Wave

Sound always propagates in waves. This results in pressure and density fluctuations in the material in which the sound travels. If a sound wave passes through the body, for example, the body tissue is briefly compressed and then relaxes again. This all happens in a fraction of a second. Since higher pressures propagate through matter faster than lower pressures, a physical phenomenon occurs known as wave steepening. If, due to high pressures, there is not a uniform, slow pressure rise and fall but a very rapid pressure change, this is also referred to as a sound or pressure pulse.

At even higher pressures, the phenomenon of steepening becomes increasingly prominent. The process of steepening bears certain similarities to water waves crashing on a beach. Unlike waves on the water surface, pressure waves in matter or tissue cannot roll over each other; instead, there is a sudden, abrupt change in pressure - a shock wave is created.

A shock wave is characterized by an extremely rapid pressure increase of approximately 10 ns (1/100 millionth of a second) and a high peak pressure of up to 100 MPa (equivalent to 1000 times the air pressure or the water pressure at a depth of 1000 meters!!!).

There are essentially two fundamentally different ways to generate shock waves or pressure pulses:

1. Pressure pulse generation with electrical energy

2. Pressure pulse generation with mechanical energy

Pressure pulse generation with electrical energy

Four different methods are used:

* electrohydraulic

* piezoelectric

* electromagnetic, flat coil/lens

* electromagnetic, cylindrical coil/reflector

What all systems have in common is that electrical energy is converted into sound waves with great technical effort and complex technology. However, this alone is not enough. To deliver the desired energy to the tissue and generate a true shock wave, the generated sound waves must be bundled in a complex manner so that they all converge at one point (the target area). This process is called focusing. Only the collision and superposition of the generated sound waves at the focal point creates the shock wave!

Pressure pulse generation with mechanical energy

Pressure pulse generation with mechanical energy is much simpler. Similar to a jackhammer, a metal body is accelerated by air pressure, which then impacts an impacting body. The impacting body rests directly on the skin, so that the sound or pressure wave generated by the impact spreads throughout the body. Focusing does not occur in this much simpler and more cost-effective procedure. Due to the lack of focus, the sound waves spread "radially" and never reach the energy required to trigger a true shock wave. The term "shock wave therapy" should not really be used for devices that work with mechanical pressure pulse generation, since a shock wave does not occur according to the physical definition.

Summary of the Different Shock Wave / Pressure Pulse Procedures for Calcific Shoulder

Rise time: approx. 0.0002 ms approx. 0.2 ms approx. 1:1000 Compression pulse duration: approx. 3 ns approx. 200–2000 ns approx. 1:1000 Positive peak pressure: approx. 0–100 MPa approx. 0.0002 ms 10:1

	Focused Shock Wave	Pressure Wave (Unfocused, Radial Shock Wave)
Focus	yes	no
Propagation	non-linear	linear
Steering	yes	no
Energy Flux Density	0–3 mJ/mm²	0–0.3 mJ/mm² approx. 10:1

Another significant difference between the two techniques is the point of maximum energy. With focused shock waves, the shock wave is only created by the superposition of the sound waves in the target area. In other tissue structures, such as the skin, only low energies occur. With a radial shock wave device or a true radial pressure pulse device, the energy peak is at the point where the sound enters the body and then loses a significant amount of energy on its way to the desired target location, depending on tissue thickness.

How can I, as a patient, distinguish between the different shock wave devices?

Even the appearance of the sound applicators (transducers) differs significantly. Due to the significantly more complex technology used for electrical pressure pulse generation and the focusing device, the transducers for true shock wave generation are significantly larger and rounded. The sound applicator usually resembles a sphere, with one half made of metal and the other half made of a soft plastic/gel that conducts the generated sound into the body.

Devices with mechanical pressure pulse generation (not a true shock wave) are usually shaped like a thick pen with a rounded metal tip at the end that is applied to the skin.

How do shock waves or pressure pulses work?

It is undisputed that shock waves and pressure pulses have a biological effect that can be used therapeutically.

A leading manufacturer writes about the effect of radial shock waves: "The currently known mechanisms of action of radial shock waves summarized mean: In the treated (pain) zone, analgesia, increased blood circulation, and reparative processes in various tissue types occur." EMS - to the corresponding page

Can shock wave treatment treat calcific shoulder? heal?

The statement: The shock wave dissolves a calcification is incorrect.

Since we are dealing with sound waves, a shock wave is not capable of dissolving anything.

The statement: The focused shock wave can contribute to the self-dissolution of calcium in the body by activating processes in the body.

Due to the fundamental differences, the radial shock wave must be clearly separated from the focused shock wave in relation to calcific shoulder.

The Radial Shock Wave for the Treatment of Calcific Shoulder

The so-called radial shock wave device (rESWT) is currently most commonly used in Germany. However, this device is not, as the name incorrectly suggests, a device for generating shock waves. In this device, mechanical energy is used to generate unfocused pressure pulses. However, to avoid confusion, we will refer to the radial shock wave (although incorrectly) from now on, rather than the correct radial pressure pulse.

During therapy, the ultrasound probe, shaped like an oversized pen with a metal tip, is moved over the painful area of ​​the shoulder. Typically, not just a single point is treated, but often a small area corresponding to the tendon insertions or an entire tendon.

Many studies have reported a significant reduction in pain after treating patients with calcific tendonitis with radial shock waves. This phenomenon is observed in many patients who experience pain in tendons or tendon insertions. For this reason, radial shock waves are a good therapy for treating, for example, chronic tendon insertion pain. However, whether radial shock waves can contribute to the dissolution of calcification has not been clearly proven in good, larger studies. It should be noted that the natural course of a calcific tendon is accompanied by the spontaneous dissolution of the calcium. The data on calcium dissolution obtained in various studies did not statistically prove that the natural course of the disease, which involves spontaneous dissolution, was superior. Many experts assume that the energy introduced into the tissue and the calcification focus by the radial shock wave is not sufficient to directly dissolve the calcification focus.

Conditions in which the calcification focus does not dissolve are problematic. Since the trigger factor of tendon pain remains, the symptoms recur after a short period of pain relief.

The high-energy, focused shock wave for the treatment of calcific tendon pain

With these devices, a complex process of generating an increase in pressure using electrical energy is carried out, which is then concentrated in the tissue by a special focusing device. The therapeutic shock wave is only created at the focal point in the tissue through superposition. These devices are usually significantly more expensive than radial shock wave devices and are therefore used much less frequently for therapy. Since a very significant amount of energy is applied in this therapy (approximately 10-30 times more than with radial shock waves), the treatment is also significantly more painful. For this reason, anesthesia is often used to make the treatment more bearable.

Because the energy is applied at a clearly defined point, the precise localization of the treatment point is necessary for focused shock waves. If you want to treat a calcification in a shoulder tendon, you ideally want the center of the energy to be in the calcification and at its borders. An X-ray image or a simple ultrasound image is far from sufficient for targeting. To enable precise targeting, the patient must first be "positioned" so that the patient, and especially the arm, cannot be moved during treatment. Movement of the arm at the shoulder would negate all previous targeting measures! Then, the calcification must be localized. Ultrasound devices or mobile X-ray machines can be used for this purpose. Once the location of the calcification has been precisely determined, the distance from the skin surface to the calcification must be determined. Only then can the shock wave applicator be adjusted so that the focus is on the calcification.

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Only by following this very complex procedure is it possible to treat the calcification precisely. Even the practitioner's considerable personal experience with shock waves can in no way replace imaging-assisted localization. Without the complex targeting, therapy is carried out "in the dark," with a pre-programmed, scientifically proven, significantly reduced success rate.

Scientific studies demonstrate a success rate for the high-energy, focused shock wave in terms of calcium dissolution that is significantly higher than the natural course. However, different studies reach very different results. The success rates for complete calcium dissolution in most studies are 20-50%.