Extracorporeal Shockwave Therapy (SWT)
Extracorporeal shockwave therapy (ESWT) is a noninvasive medical treatment that utilizes acoustic waves to address various conditions, including kidney stones, tendinitis, and pain in the neck and lower back. The therapy employs a device known as a shockwave gun, which transmits low-energy shockwaves to the affected area through the skin, often with the aid of a topical gel. Sessions typically last between 5 to 15 minutes, and while side effects are minimal, some patients may experience discomfort during treatment.
Originating from research on the use of shockwaves for kidney stone lithotripsy in the 1980s, ESWT has evolved to support the healing of soft tissue and bone injuries. It is categorized into focused, radial, and defocused applications, with focused ESWT being the most effective for targeted regeneration. However, focused applications require skilled administration and ultrasound guidance, making them more costly.
While the FDA has approved ESWT for several conditions, coverage by insurance can vary. The precise mechanisms of how ESWT promotes healing and pain relief are still under investigation, but it is thought to stimulate cell signaling and blood vessel formation, leading to reduced inflammation and pain management. ESWT is also being explored for additional applications, including cosmetic treatments and erectile dysfunction.
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Extracorporeal shockwave therapy (ESWT)
Extracorporeal shockwave therapy (ESTW) is a noninvasive treatment for a variety of conditions including kidney stones, tendinitis, and neck and lower back pain. It uses acoustic waves generated by a device often called a shockwave gun. Treatment generally takes several minutes and leads to few side effects. ESTW offers several advantages, including its noninvasive nature and accelerated healing of soft tissues. Despite its benefits, insurance companies often will not approve ESTW for treatment of some conditions.
Background
Researchers first began investigating the potential use of acoustic shockwaves to treat human tissue during the 1960s and 1970s. By the early 1980s, extracorporeal (meaning “outside the body”) shockwave lithotripsy came into common use. Lithotripsy uses shockwaves to break up kidney stones in the kidney and ureter (the tube that carries urine from the kidneys to the bladder). It was the first noninvasive technique to treat conditions of human tissues—that is, the treatment is external to the body but treats a condition internal to the body.
Given the newness of the technology and lack of underlying research, scientists were concerned about the effect of the shockwaves on bone, particularly hip bones, which are situated below the kidneys. This concern led to research on the effect of shockwaves on bony tissue, which showed that the shockwaves had a regenerative effect on bone formation.
ESWT also showed a healing effect on soft tissue. This discovery led to further research into the other potential uses of shockwave therapy, resulting in the development of ESWT for an increasing number of conditions. ESWT remains a common treatment for kidney stones and is often used to accelerate the healing of injuries to soft tissue, such as tendinopathies, tendinitis, and plantar fasciitis.
Overview
ESWT transmits low-energy acoustic waves via an instrument commonly known as a shockwave gun that is placed on the patient’s skin in the treatment area; a topical gel applied to the skin assists in the transference of energy. Early devices used an electrohydraulic mechanism, while later devices used electropneumatic (compressed air), piezo-electric (the same mechanics used in a cigarette lighter), or electromagnetic force to accelerate a projectile within a guiding tube up to 50 to 60 mph (80 to 96 kph). The projectile then impacts a metal applicator. The kinetic energy created by the impact is converted by a transducer into a radio shockwave.
Treatment with ESWT usually lasts 5 to 15 minutes with few side effects. Although most patients do not have any associated pain, some may experience discomfort at the application site. The US Food and Drug Administration has approved the use of ESWT to treat numerous conditions, but some conditions may not be covered by insurance. ESWT should only be applied by a highly skilled clinician, as misapplication can lead to adverse effects.
ESWT can be applied as a focused, radial, or defocused therapy. Focused application of ESWT uses the highest energy level; it can pinpoint a specific target to within 0.04 inches (1 mm). It can penetrate tissue more than 4 inches (10 cm). Radial ESWT provides a lower level of energy across a broader area and can penetrate about 0.6 inches (1.5 cm). Defocused ESWT, also called planar or softwaves, uses the lowest level of energy with broad dispersal and minimum penetration. It is mostly used for cosmetic treatments, for example, to treat cellulite. Focused application of ESWT has the most regenerative effects—roughly 70 percent and 50 percent higher than radial and defocused applications, respectively.
Despite its effectiveness, focused ESWT has some disadvantages. First, due to the necessity for precision, focused ESWT must be applied with the guidance of ultrasound, creating the need for a highly skilled clinician. Second, it is more expensive than radial or defocused ESWT. The primary disadvantage of radial application is that the shockwaves dissipate rapidly and do not penetrate very deeply. In fact, researchers have debated whether radial and defocused applications are accurately described as ESWT because the low-energy shockwaves dissipate so quickly. However, evidence shows that radial and defocused ESWT are effective treatments for some conditions, particularly spasticity (for example, in cases of stroke or multiple sclerosis) and cosmetic improvements, respectively.
The mechanics of ESWT are not well understood, but researchers have hypothesized that the healing effects of the therapy occur in four stages. First, in the physical phase, the shockwaves stimulate the transmission of energy to cells and tissue. Second, in the physiochemical phase, ESWT prompts the release of biomolecules that activate the cell signaling pathways. Third, in the chemical phase, the shockwaves alter the function of ion channels in cell membranes. Finally, in the biological phase, ESWT causes angiogenesis (the formation of new blood vessels), which positively influences the healing of bone and soft tissue.
The reason that ESWT can reduce or eliminate pain is also unclear. Researchers have suggested two possibilities. First, the shockwaves may decrease the formation of nerve fibers, thus also decreasing the development of pro-inflammatories, leading to reduced inflammation and pain. Second, the shockwaves may trigger the release of endorphins, which have an analgesic (pain-reducing) effect.
Besides its use to break up kidney stones, all other applications of ESWT are regenerative. The list of conditions ESWT can be used to treat include shoulder tendinopathy, lateral epicondylosis/epicondylitis, greater trochanteric pain syndrome, hamstring tendinopathy, patellar tendinopathy, medial tibial stress syndrome, myofascia (the dense, tough material that covers bones and muscles) pain, carpal tunnel disorder, Achilles tendinopathy, plantar fasciitis, knee osteoarthritis, non-union fracture, scars, bone edema, neck and lower back pain, trigger points, tennis elbow, and spasticity of spinal and supraspinal origin (stroke, brain injury, multiple sclerosis, cerebral palsy). ESWT has also been studied as a noninvasive way to treat erectile dysfunction.
Bibliography
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