Definition and Overview
Extracorporeal shock wave therapy (ESWT) is a non-invasive regenerative treatment that delivers high-energy acoustic waves (shock waves) generated by electrohydraulic, piezoelectric, or electromagnetic methods in focused or radial form to target tissues, inducing tissue regeneration, pain relief, and angiogenesis.
A shock wave is a single acoustic pulse characterized by rapid pressure rise and fall, with microsecond-duration waveforms unlike sinusoidal waves. This physical property delivers mechanical stimulation to biological tissues, triggering cellular responses.
ESWT was first used for urolithiasis fragmentation in the 1980s, and its indications have since expanded to musculoskeletal conditions. It is now an established non-invasive treatment for chronic musculoskeletal pain including plantar fasciitis, calcific tendinitis, and tendinopathy.
Mechanism of Action
The main biological mechanisms of ESWT include:
Mechanotransduction: mechanical stimulation from shock waves is converted into biochemical signals through cell receptors, promoting growth factor (TGF-beta, VEGF, IGF-1) secretion and inducing collagen synthesis and tissue regeneration.
Angiogenesis: achieved through increased VEGF secretion, contributing to improved blood supply in chronic tendinopathy tissue.
Pain modulation mechanisms include hyperpolarization of unmyelinated C-fibers and A-delta fibers, decreased neuropeptide (substance P) levels, and elevated pain thresholds [4].
Cavitation: microbubble formation and collapse during shock wave delivery produces localized mechanical effects, involved in calcification breakdown in calcific tendinitis.
Indications
Plantar fasciitis is the prototypical ESWT indication, applied for chronic plantar fasciitis that fails conservative treatment (stretching, insoles, physical therapy). Studies report approximately 60-80% pain improvement at 3-month follow-up [1].
For calcific tendinitis, calcification breakdown and absorption are confirmed. Gerdesmeyer et al. (2003) demonstrated significant pain reduction and calcification resolution versus placebo in a randomized controlled trial [2].
Tendinopathy indications include lateral epicondylitis (tennis elbow), Achilles tendinopathy, and patellar tendinopathy (jumper's knee) [4].
Other applications include chronic musculoskeletal pain, myofascial pain syndrome, and research-stage applications for erectile dysfunction, peripheral vascular disease, and nerve regeneration.
Procedure
Pre-procedure ultrasound or clinical examination precisely identifies the treatment target area.
Focused ESWT uses a focused transducer to concentrate energy at the target tissue depth, with energy flux density (EFD) and impulse count set per protocol.
Radial ESWT uses a handpiece applied directly to the skin, generating shock waves by accelerating a projectile with compressed air. Energy disperses near the skin surface.
Standard protocols typically involve weekly sessions, 3-5 treatments total, delivering 1,000-3,000 impulses per session. Treatment time is approximately 10-20 minutes.
Efficacy and Evidence
For plantar fasciitis, Rompe et al. demonstrated significant pain reduction with ESWT in patients failing conservative treatment [1]. Multiple meta-analyses consistently confirm ESWT efficacy for plantar fasciitis.
For calcific tendinitis, Gerdesmeyer et al. (2003) multicenter RCT showed statistically significant superiority of high-energy ESWT over placebo in VAS pain scores and calcification resolution [2].
For tendinopathy, Maffulli et al. (2011) review confirmed significant pain and functional improvement with ESWT for chronic tendinopathies including Achilles tendinopathy [4].
Low-energy ESWT may be less effective than high-energy but has a better safety profile [3].
Precautions and Contraindications
Absolute contraindications include bleeding disorders, anticoagulant use (warfarin), local infection at the treatment site, malignancy (cancer), and pregnancy.
Relative contraindications include treatment near open growth plates in patients under 18, over implanted metal hardware, and areas with neurological sensory deficits.
Post-procedure: rest the treatment area for several days, limit vigorous exercise, and avoid concurrent steroid injections as they may reduce effectiveness.
Complications are rare but may include bruising (petechiae), temporary pain increase, and rarely skin damage.