While FSW and RPW both impact tissue via acoustic waves, they are generated by different mechanisms and have unique physical characteristics. FSW machines generate shock waves using either electrohydraulic, electromagnetic, or piezoelectric technology. The waves are focused through a lens and transmitted into the tissue via the handpiece. The focused waves allow for targeted application and for deep tissues to be reached up to about 4.7”. Focused shockwaves are characterized by a single positive pressure pulse (usually in the range of 10-100 MPa) and then followed by a small negative tensile wave. 2
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Shockwave
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Radial Pressure Wave
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Time (us)
Radial pressure waves, on the other hand, have a significantly lower peak pressure pulse (usually 0.1 to 1 MPa) so they are not technically a shockwave in physics terms. 2 Most RPW machines generate radial pressure waves using a pneumatic system. During use, compressed air is released via a valve into the barrel of a hand-held applicator which contains a small projectile. The projectile is driven by the compressed air into a transmitter at the end of the applicator where the kinetic energy is converted into acoustic waves at the skin surface. The waves then travel radially into the adjacent tissue, hence the name radial pressure wave. Because these waves propagate outward from the transmitter, they stay closer to the surface of the skin affecting more superficial tissues.
Wave Generation:
Electrohydraulic Piezoelectric Electromagnetic
Pneumatic
Focus Shockwave
Radial Pressure Wave
Waves stay closer to the surface
Waves reach greatest depth
Skin Surface
Target Zone
Target Zone
Convergent Waves
Divergent Waves
It can be confusing that RPW falls under the umbrella term of ESWT since it is not an actual shockwave. However, since FSW and RPW affect tissue in the same way, and they can produce similar results when used at the same dose for musculoskeletal conditions, 3 both waveforms are commonly referred to as shockwaves. Regardless of terminology, the critical point to understand is that both FSW and RPW have a wealth of studies demonstrating their effectiveness in treating multiple musculoskeletal conditions, 3,4 and they have made a name for themselves in the rehabilitation, physical therapy, and chiropractic fields. Read on for summaries of recent research supporting the use of shockwave therapy for common clinical conditions.
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