What Studies Say About Shockwave Therapy

By David Zuckerman, DPM

As podiatric physicians and surgeons, we would like to treat chronic plantar fasciitis without the risks and complications that are inherent to common plantar fascia releases. We have studied lower extremity biomechanics and have been taught that with all surgical procedures, we must understand and respect the function of the human foot and how each surgical procedure changes its specific function and stability.
However, studies of extracorporeal shockwave therapy (ESWT) have proven that we can cure chronic, insertional plantar fasciitis without exposing patients to any of the known risks (ranging from infection and nerve entrapment to reflex sympathetic dystrophy (RSD) and calcaneal-cuboid syndrome) associated with any type of surgical plantar fascia release.

How Do Shockwaves Work?
So how does this noninvasive treatment work? Well, there is nothing mystical or cryptic about a shockwave. It is nothing more than a sonic boom. A shockwave is produced by electromagnets generating a signal through water. The signal is directed through a lens to direct all of the energy to a single focal point. Using an ESWT device enables you to place the patient’s foot on that focal point, where it receives all the directed energy to the damaged tissue.
A shockwave has certain physical characteristics. There is a high peak pressure (sometimes more than 100 Mpa), but the average pressure of shockwaves is approximately 50 Mpa with a short lifecycle of approximately 10 ns. In addition, there is, by definition, a fast initial rise in pressure of less than 10 ns and a broad frequency spectrum that is typically in the range of 16-20 Hz.
When a shockwave enters tissue, it may break up and reflect the absorption of kinetic energy by the precise body structures (bone, fat, tendon, ligaments), which are exposed to the shockwave.1 All techniques of shockwave production (electrohydraulic, electromagnetic and piezoelectric) depend on the conversion of electrical energy to mechanical energy.1
When a sound wave is transmitted into tissue, there are two levels of transmission: low energy and high energy. Low energy has an analgesic effect by either disrupting the cell membranes partially or completely. When high energy (any energy greater then 0.28mJ/mm2) comes in contact with the damaged tissue, there is a direct biological interaction. The body will react by increasing blood flow to the area, initiating vascular neogenesis and a reparative cycle. When you apply high energy to the insertion of a damaged plantar fascia, the reparative healing begins. This process leads to fibroblastic production and new healthy tissue in the area that was once avascular tissue.

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