The Swiss DolorClast® Principle
EMS began researching the effect of pneumatically generated shock waves on bone tissue as early as 1990. Based on the Swiss LithoClast – a highly effective extracorporeal lithotripsy device used in urology with over 8,000 units in daily use – EMS introduced the Swiss DolorClast and set a new standard in extracorporeal shock wave therapy.
Based on an entirely new concept in the treatment of musculoskeletal soft tissue pain, the Swiss DolorClast is a modified Swiss LithoClast device, producing shock waves in the low to medium energy range, similar to those used in intracorporeal lithotripsy.
A projectile in the handpiece is accelerated at high speed using a precisely controlled pulse of compressed air. The projectile is directed with a tolerance of a few micrometers. When the projectile strikes the applicator inside the handpiece its kinetic energy is converted into mechanical energy.
This energy is transmitted along the applicator. At the end of the applicator, the shock wave is coupled to human tissue. To minimize transmission losses - which would occur in the air between applicator and skin interface – contact gel is used to guide the shock wave.
Among 202 physicians surveyed worldwide on their use of Swiss Dolorclast, more than 90% stated they would choose to use the therapy again. Asked whether they would accept to repeat the treatment, an overwhelming 91% of patients responded in the affirmative due to the therapy’s remarkable decrease in pain after a short time.
How does Swiss DolorClast work?
Physical Principles
Shock waves are defined as transient pressure oscillations that propagate in three dimensions and typically bring about a clear increase in pressure within a very short time. In most units used in medicine, such maximum pressure is reached within a few nanoseconds. Besides this very rapidly rising positive pressure impulse, shock waves are also characterized by a tension phase with negative pressure following the pressure phase. A complete shock wave lasts from a few microseconds to milliseconds; the frequency spectrum ranges from 16 Hz to 20 MHz.
All methods used to generate shock waves aim to couple the pressure impulse to the tissue while minimizing energy loss. One of the latest but also very common methods is the mechanical generation of shock waves. Based on ballistics, compressed air accelerates a projectile which hits an applicator placed on the skin at very high kinetic energy. By using a coupling gel, such impact pressure is delivered directly to the tissue in the form of a pressure wave. This wave travels in a radial fashion, thus the term “radial shock wave”.
In radial shock wave generation, the applicator surface constitutes the geometric point of highest pressure and highest energy density. Due to radial expansion, the pressure and energy density of the shock wave drop steadily upon leaving the applicator as it passes through tissue. Radial shock wave therapy is therefore highly appropriate to treat indications near the surface. In contrast, focused technologies are required to treat deep areas.
Typically, a shock wave features a very steep and short ascent until maximum pressure results from asymmetric attenuation when traveling through tissue. Referred to as steepening, this phenomenon is the result of differences in attenuation of individual frequency parts of the shock wave front and of pressure- and temperature-dependent acoustic conduction velocity. Different tissue media respond differently to impedance, the tissue-typical resistance to acoustic conductivity. Such impedance differences occur at the interface of tissue media with different physical properties such as calcium deposit/soft tissue or bone/soft tissue interfaces.
At these acoustic interfaces, acoustic energy is transformed into mechanical energy. The release of mechanical energy leads to mechanical effects such as calcium deposit disintegration. The portion of acoustic energy transformed into mechanical energy varies with the difference in impedance. If, for example, a shock wave travels through water with an average impedance of 1.49 Ns/m3 and reaches a medium of higher impedance such as kidney stones (up to 15 Ns/m3), most of the acoustic energy is transmitted to the stone. A difference in impedance amplitude determines the direct mechanical effect of the shock wave.
The mechanical pressure and tension force brought to bear on the affected tissue creates an increase in cell membrane permeability, thereby increasing microscopic circulation to the tissues and the metabolism within the treated tissues, both of which promote healing and subsequent dissolution of pathological calcific deposits.
An important indirect mechanism is the induction of cavitation. Cavitation is defined as the occurrence of gas-filled bubbles if negative pressure gradients exist. Such negative pressure cavities occur if cohesion of liquid media, such as water, is below positive pressure forces. The predominant negative pressure causes the liquid to evaporate at the edge of the cavitation bubble, thus causing cavitation bubbles to increase even further. When the pressure wave has passed the tissue, pressure returns to normal isobar conditions and the bubble collapses again. As thousands of these bubbles burst, the resultant force is strong enough to help break down pathological deposits of calcification in soft tissues.
Biological (Molecular/Cellular) Mechanisms
Beyond breaking down pathological calcific deposits, ESWT has been shown to stimulate osteoblasts, responsible for bone healing and new bone formation, and to stimulate fibroblasts, responsible for the healing of connective tissues such as tendons, ligaments and fasciae.
ESWT also diminishes pain. It initially reduces pain through what is known as hyperstimulation anesthesia. The nerves sending pain signals to the brain are stimulated to such an extent that their activity diminishes, thereby decreasing or eliminating pain.
When activated, the so-called C nerve fibers – responsible for transmitting pain – release substance P in the tissue as well as in the spinal cord. Substance P – a pain mediator and growth factor – is responsible for causing slight discomfort during and after shock wave treatment. However, with prolonged activation, C nerve fibers become incapable for some time of releasing substance P and causing pain.
Shock waves lead to the depletion of substance P from free nerve endings. Less substance P in the tissue leads to reduced pain. But less substance P also causes so-called neurogenic inflammation to decline. A decline in neurogenic inflammation may in turn smooth the way to healing – together with the release of growth factors such as bone morphogenetic protein (BMP), vascular endothelial growth factor (VEGF) and proliferating cell nuclear antigen (PCNA), and the activation of stem cells in the treated tissue. While the process explains the long-lasting analgesic effect of shock waves, substance P has also been shown to stimulate angiogenesis and capillarization, stimulate neovascularization and contribute to tissue regeneration and new bone formation.
Extracorporeal shock waves produce a regenerative or tissue-repairing effect in musculoskeletal tissues, not merely a mechanical disintegrating effect. They appear to stimulate the release of angiogenic growth factors and the ingrowth of neovascularization and improvement in blood supply leading to repair of tendon and bone.
