Extracorporeal shock wave therapy (ESWT) is a safe therapy with just a few documented adverse effects, such as pain during ESWT and small hematomata, but no serious consequences can be expected if administered according to the instructions.
The effect mechanism of ESWT is still being studied, but as far as we can tell, it works in a similar way to a mechano-transduction-triggered cascade: mechanical energy causes changes in the cellular skeleton, which causes a reaction of the cell core to influence diverse cell structures, resulting in an enzymatic response that improves the healing process.
To improve the outcome, the use of ESWT should be taught. Because the legislative framework circumstances vary from one country to the next, courses should be offered by national organizations.
The following musculoskeletal indications (primarily bone and tendons) are addressed in this update: pseudoarthrosis, delayed fracture healing, bone marrow edema and osteonecrosis in its early stages, insertional tendinopathies such as plantar fasciitis and Achilles’ tendon fasciitis, rotator cuff calcifying tendonitis, tennis elbow, and wound healing problems.
Extracorporeal shock wave therapy (ESWT) is a non-invasive treatment method that evolved from ESWL extracorporeal shock wave lithotripsy. The development of EWST, as well as the physical theoretical foundation knowledge and various devices for application, such as focusing devices (electro-hydraulic, piezo-electric, electro-magnetic flat, electro-magnetic cylindric) and radial devices, also known as ballistic, began with initial applications that were tested on bones by orthopedic surgeons and traumatologists in Germany and Bulgaria. Several researchers in various areas independently discovered and attempted to use the effects of shock waves on bones. Many new indications for ESWT have evolved quite fast in orthopedics, in addition to the application to the bone, and ESWT has grown significantly.
In 1997, the unbridled enthusiasm for ESWT as a type of therapy, combined with a lack of verified proof, led to skepticism of the therapy, particularly in the country where ESWT is most commonly used. The report of the Federal Committee of Doctors and Health Insurance Funds’ ‘Medical Treatment’ working committee on consultations from the year 1998 for the evaluation of extracorporeal shock wave therapy for orthopedic, surgical, and pain therapeutic purposes resulted in the elimination of payment for this treatment by health insurance funds in Germany.
Extracorporeal shock wave lithotripsy gave rise to extracorporeal shock wave therapy (ESWL). Studies on the impact of shock waves on the various tissues of the body that come into direct or indirect contact with shock waves have also focused on bones and other musculoskeletal tissues, demonstrating that shock waves can have a favorable influence on a wide variety of tissues.
Devices Used for Extracorporeal Shock Wave Therapy
The development of ESWT devices is inextricably related to the development of ESWL devices (Fig. 1). The electro-hydraulic devices were first introduced to the market, followed by the piezoelectric and different electromagnetic devices (with flat coil or cylindrical coil). All of these devices generate pressure pulses that concentrate. There are significant variances in the quality of the sound fields, particularly the focus zones, yet shock waves can be generated with any of these devices at the greatest energy levels. The radial devices use compressed air or electromagnetic forces to accelerate a ‘projectile’ within the device, which then transfers its energy to the tissue when it collides with an applicator.
The transmission of a shock wave or a pressure wave causes tissue consequences. A cascade process is akin to the transfer of physical energy into a biological response. The activation of the cell skeletal annexes causes the release of mRNA from the cell nucleus. This is followed by the activation of cell organs such as the mitochondria and endoplasmic reticulum, as well as cell vesicles, which release the healing-specific proteins. Wang’s research team demonstrated many working mechanisms that fit into the theory of mechano-transduction, as ESWT users refer to the cascade. ESWT generates free radicals and oxygen radicals in animal models, which cause the creation of a variety of growth factors.
A biomechanical issue is the fixed action of screws or implants in osteoporotic bone. To prevent osteoporosis, several treatments such as bone impaction, angular stable plates, coatings, and cement augmentation have been tested. Local bone induction is another possibility. Local shock wave therapy was used in a rat study, and it was discovered that there was an increase in bone density evaluated in micro-CT not just in the area of the screws, but also far away from them. In the pull-out test (3000 unfocused shock waves with an energy density of 0.3 mg/mm2), increased stability was also found.
ESWL has been used by urologists to break up kidney stones. The remaining uses are all regenerative. This must be explained to the patient, and it also has an impact on the post-ESWT recommendations. If ESWT is used to treat tendons or bones, for example, proper precautions must be taken to ensure that stress does not interfere with the healing process. ESWT can speed tissue healing, as can be shown from the mechanisms of action, but essential rules must still be followed, such as immobilization during bone repair, or regenerate tissue would be damaged with every movement of the fracture gap. It’s critical to emphasize to the patient that recovery takes time.
Extracorporeal shock wave therapy is a non-invasive treatment for musculoskeletal diseases that evolved from extracorporeal shock wave lithotripsy. This review article covers the fundamentals of ESWT, including its historical evolution, physical theoretical foundations, and many application devices. The effect of ESWT on cells and its molecular mechanisms are discussed in the portion of the text. Non-union, delayed healing, osteochondrosis dissecans, osteonecrosis, bone marrow edema, plantar fasciitis, Achilles tendinopathy, epicondylitis radialis, and trigger points are all examples of bony indications. ESWT, in our opinion, is a viable conservative therapeutic option for the conditions discussed in this review. This option, however, should only be used by orthopedic doctors who are knowledgeable about this therapy and these indications. Nonetheless, more randomized studies are needed in some areas to strengthen the evidence.