What Is Extracorporeal Shock-Wave Therapy?
Extracorporeal shockwave therapy (ESWT) is a non-invasive treatment that uses acoustic shockwaves to provide therapeutic benefits in various musculoskeletal conditions. Shockwaves are sound waves characterized by a rapid spike in positive pressure followed by a negative pressure phase. They can be generated using electromagnetic, electrohydraulic, or piezoelectric systems and delivered to the target tissue via a probe applied to the skin.
Extracorporeal shockwave therapy (ESWT) has become an increasingly utilized treatment approach in orthopedics and rehabilitation over the past few decades. This article provides an overview of ESWT, including the history of its development, proposed mechanisms of action, and current clinical applications.
How Was Extracorporeal Shock-Wave Therapy First Developed?
ESWT originated in the early 1980s as an extracorporeal technology for breaking up kidney stones, also known as extracorporeal shockwave lithotripsy (ESWL). The focused shockwaves transmit mechanical energy deep into the tissue, generating forces strong enough to fragment urinary calculi. Orthopedists soon realized ESWT had potential applications for musculoskeletal conditions as well. Early animal research in the 1980s indicated that ESWT could aid in the loosening of prosthetic cement, the improvement of bone-cement interfaces, and the enhancement of bone repair. In the 1990s and 2000s, most orthopedic research shifted from bone to soft tissue applications, exploring the use of ESWT for tendinopathies, fasciopathies, and other extremity conditions. Though protocols remain varied, ESWT is now primarily used as a non-invasive treatment approach for chronic tendinopathies and other common orthopedic conditions.
What Are the Biological Effects of Extracorporeal Shock-Wave Therapy on the Body?
The shockwaves from ESWT cause physical forces on the cells. The physical energy from ESWT sets off a molecular cascade in the cells through mechanotransduction. The shockwaves activate parts of the cell, like the cytoskeleton and nuclei. This makes the cell release healing proteins and growth factors.
Some main effects are:
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More growth factors tell cells to grow and divide.
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Stem cells are activated and multiply.
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Bone density improves, and bone tissue regenerates.
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Cartilage, tendons, and wounds heal better.
What Is the Mechanism of Action Of Extracorporeal Shock-Wave Therapy?
Shockwaves are acoustic waves characterized by a rapid initial spike in positive pressure, followed by a lower amplitude negative pressure phase. As the wave propagates through tissue, the positive phase generates direct mechanical forces while the negative phase forms transient cavitation bubbles. The combination of these mechanical and cavitation effects appears to trigger a biological response.
The exact mechanisms through which ESWT provides clinical benefits remain partially elucidated. Proposed mechanisms include:
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The shockwaves may promote neovascularization – the formation of new blood vessels – in chronically degenerated tendons and other tissues. The improved blood supply brings oxygen, nutrients, and reparative cells to kickstart healing.
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ESWT has been shown to stimulate the proliferation and differentiation of tenocytes, osteoprogenitors, and other cells involved in regeneration. By activating these cell populations, ESWT boosts the number of cells available for repair.
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The mechanical forces and cavitation effects of shockwaves seem to trigger a mild inflammatory response, marked by increased inflammatory mediators and infiltration of leukocytes. This controlled inflammatory phase is a key step in healing injured or degenerated tissue.
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Studies demonstrate that ESWT amplifies the synthesis of endogenous growth factors like VEGF, BMP-2, and IGF-1. These proteins play crucial roles in tissue regeneration by signaling cells to proliferate, differentiate, and migrate to the site of injury.
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ESWT appears to regulate matrix remodeling through effects on MMP activity and collagen synthesis. MMPs break down pathological matrices while new collagen production restores the proper tissue structure.
What Are the Clinical Applications of Extracorporeal Shock-Wave Therapy?
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Tendinopathies in both the upper and lower extremities are the main location of application, including rotator cuff tendinitis (shoulder tendon inflammation), Achilles tendinitis (ankle tendon inflammation), and patellar tendinitis (knee tendon inflammation). The shockwaves target chronic degeneration and micro ruptures within the tendon to provoke a healing response.
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Fasciopathies, especially plantar fasciitis are another well-studied application. Plantar fasciitis is inflammation of the band of tissue running along the bottom of the foot. ESWT can help when other treatments fail to relieve heel pain from plantar fasciitis.
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ESWT is also used to treat deeper tissue issues like gluteal tendon inflammation and medial tibial stress syndrome. Gluteal tendon inflammation (greater trochanteric pain syndrome) causes pain in the outer hip/pelvis area due to irritated tendons. Medial tibial stress syndrome is an overuse injury of the posteromedial tibia.
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In terms of bone disorders, ESWT can treat delayed fracture healing and non-union (failure to heal broken bones) by stimulating osteoblast activity and bone formation. There is also early evidence that it may help with avascular necrosis (death of bone tissue due to lack of blood supply).
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Osteoarthritis is a common joint disease causing cartilage breakdown and inflammation. ESWT has improved pain, function, and quality of life in knee osteoarthritis patients. It may regenerate cartilage and reduce inflammation.
What Are the Contraindications of Extracorporeal Shock-Wave Therapy?
Though a non-invasive treatment, ESWT does have some contraindications where it should be avoided.
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Over-Sensitive Areas Like Growth Plates in Children or Teens- It should not be applied over sensitive areas like growth plates in children and teenagers whose bones are still maturing.
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Pregnancy- It is a contraindication due to unknown effects on the fetus.
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Pacemakers or Implants- Those with pacemakers, defibrillators, or joint implants are also not candidates because the shockwaves may interfere with these devices.
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Anticoagulation- Patients on anticoagulation medications are at higher risk of bleeding from ESWT.
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Local Tumors- The treatment should also be avoided around local tumors and infections to prevent spreading.
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Local Infection- Open wounds should be avoided as well until healed due to infection risk.
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Neuropathy- Those with neuropathy or numbness in the area may not feel pain that could cause further injury.
Conclusion
In conclusion, extracorporeal shockwave therapy is a promising treatment approach for various chronic musculoskeletal conditions. Though originally developed for breaking up kidney stones, orthopedic applications now predominate. Research continues to uncover its mechanisms of action, which appear to involve neovascularization, cell proliferation, inflammatory signaling, and matrix remodeling. While treatment protocols are still being optimized, ESWT provides a non-invasive option for tendinopathies, fascial disorders, bone healing, and osteoarthritis. Further high-quality studies will refine appropriate usage and standardize parameters. However, the existing evidence supports ESWT as an effective therapy for common orthopedic issues where conservative care has failed.
