Definition and Overview
Extracorporeal shock wave therapy (ESWT) is a non-invasive regenerative treatment that induces tissue regeneration, pain relief, and angiogenesis by delivering high-energy acoustic waves (shock waves) generated outside the body using electrohydraulic, piezoelectric, or electromagnetic methods to target tissues in a focused or radial form.
A shock wave is a single acoustic pulse in which pressure rapidly rises and then falls, and unlike a sine wave, it has a short waveform in the microsecond unit. This physical property transmits mechanical stimulation to biological tissues and triggers cellular responses.
Since ESWT was first used to crush urinary stones in the 1980s, its indications have expanded to include musculoskeletal diseases, and it is currently established as a major non-invasive treatment for chronic musculoskeletal pain such as plantar fasciitis, calcific tendinitis, and tendinopathy.
Mechanism of Action
The main biological mechanisms of ESWT are as follows.
Mechanotransduction is the process by which the mechanical stimulation of shock waves is converted into biochemical signals through cellular receptors. Through this, the secretion of growth factors (TGF-β, VEGF, IGF-1) is promoted, leading to collagen synthesis and tissue regeneration.
Angiogenesis is achieved through increased secretion of VEGF (vascular endothelial growth factor) and contributes to improving blood flow to chronic tendinopathy tissues.
Pain control mechanisms have been proposed to include hyperpolarization of unmyelinated C-fibers and Aδ-fibers, reduction of neuropeptides (substance P), and increase of pain threshold.
The cavitation phenomenon causes local mechanical effects as fine bubbles are formed and collapsed during the shock wave transmission process, and is involved in lime decomposition in calcific tendinitis.
Indications
The main indications for ESWT are as follows.
Plantar fasciitis is a representative indication for ESWT, which is applied to chronic plantar fasciitis that does not respond to conservative treatment (stretching, insoles, physical therapy). In the study, pain improvement of approximately 60-80% was reported at 3-month follow-up.
In calcific tendinitis, the effect of promoting calcium decomposition and absorption has been confirmed, and Gerdesmeyer et al. (2003), in a randomized controlled trial, significant pain reduction and calcium disappearance were observed compared to placebo.
Tendinopathy applies to lateral epicondylitis (tennis elbow), Achilles tendinopathy, and patellar tendinopathy (jumper's knee).
Other applications for chronic musculoskeletal pain, myofascial pain syndrome, and in the research phase, erectile dysfunction, peripheral vascular disease, and nerve regeneration are also being explored.
Treatment method
Before the procedure, the treatment target area is accurately confirmed through ultrasound or clinical examination.
Focused ESWT uses a focused transducer to focus energy at the target tissue depth. Energy flux density (EFD) and impulse count are set according to the protocol.
Radial ESWT generates shock waves by accelerating a projectile with compressed air by placing the handpiece in direct contact with the skin. Energy is distributed close to the skin surface.
The standard treatment protocol is generally once a week, 3 to 5 times, and each treatment delivers 1,000 to 3,000 shocks. The treatment time is approximately 10 to 20 minutes.
Effectiveness and Evidence
In a study by Rompe et al. for plantar fasciitis, ESWT significantly reduced pain in patients who failed conservative treatment. The effectiveness of ESWT for plantar fasciitis has been consistently confirmed in several meta-analyses.
For calcific tendinitis, Gerdesmeyer et al. (2003) in a multicenter RCT showed statistically significant superiority of high-energy ESWT compared to placebo in terms of pain score (VAS) and calcium loss.
For tendinopathy, Maffulli et al. (2011)'s review confirmed that ESWT has a significant pain and functional improvement effect in chronic tendinopathy such as Achilles tendinopathy.
Low-energy ESWT may be less effective than high-energy, but its safety is higher.
Precautions and contraindications
Absolute contraindications include blood coagulation disorders, taking anticoagulants (warfarin, etc.), local infection at the procedure site, malignant tumor (cancer), and pregnancy.
Relative contraindications include surgery near the epiphyseal plate (growth plate) under the age of 18, on implanted metal fixtures, and in areas with decreased sensation due to neurological disease.
Precautions after the procedure include resting the treated area for a few days after the procedure, limiting strenuous exercise, and avoiding concurrent steroid injections as much as possible as this can reduce the effectiveness.
Complications of the procedure are rare, but bruising (petechiae) at the procedure site, temporary increased pain, and rarely skin damage have been reported.
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