Cath Lab Digest

   The piezoelectric principle employs a high voltage current, which is applied to a substantial number of piezo crystals mounted on the inside of a sphere. The piezoelectric effect causes deformation of the crystals, inducing a shockwave. The focal point or area of maximal therapeutics is at some fixed distance away from the shock wave generator in the electrohydraulic, electromagnetic and piezoelectric machines.

   The radial principle has a focal point that differs from the other three technologies. The focal point of the radial principle is directly at the device-skin interface and is dispersed in a megaphone fashion from the head of the radial device.

   There have been several proposed theories when it comes to the mechanism of action of shockwave. Research by Wang described the mechanism of MSK-ESWT as multiple microtraumas that promote neovascularization to the tissue that one is treating. Others have compared the process to that of tenderizing meat whereby repeated pounding on the meat will break up the interstitial fascia or scar tissue, and make the meat more pliable.

   In a study of the Achilles tendons of mongrel dogs versus a placebo, Wang showed that shockwave not only promotes neovascularizaton but also facilitates the release of growth factors PCNA, VEGF and eNOS. Shockwave treatments have been employed for several different MSK applications including the treatment of tendonitis, calcifying tendonitis, periarticular shoulder calcification, plantar fasciitis, medial and lateral epicondylitis, osseous non-unions and avascular necrosis.

   Currently, there is no consensus on the use of low-energy shockwaves, which do not require local anesthesia, and high-energy shockwaves, which require local or regional anesthesia for the treatment of chronic plantar fasciitis. There is no consensus for differentiating between low-energy and high-energy shockwaves as multiple physical parameters are involved.

   While the clinical effect of both protocols appears to be comparable, there is clear evidence of increasing side effects as the energy level increases. Although these side effects do not appear to be significant from a macroscopic view, local tissue and nerve tissue may be affected. No local anesthesia is required for low-energy shockwaves so related side effects are lacking.

   The only “disadvantage” of low-energy shockwaves is that one has to provide a repeat application. A comparison of the effectiveness of low-energy and high-energy shockwaves has not been studied.

Shockwave Therapy Or Surgery For Chronic Plantar Fasciitis?

   Why have surgeons continued to change their procedure of choice over the years despite citing literature with good to excellent early results? It is probably the same reason why there are over 100 bunion operations. They are searching for the procedure that is predictable over the long term with the least amount of complications and disability for the patient.

   We have certainly heard surgeons proclaim minimally invasive surgery as being 95 percent successful with immediate weightbearing and no complications. Certainly, those statistics are far from reality. Whenever one performs invasive surgery, there are risks. It is not uncommon to hear of the patient who underwent an endoscopic plantar fasciotomy (EPF) and wound up having severe nerve injury to branches of the plantar nerve.

   We have also encountered the patient who had open sectioning of the plantar fascia and removal of the bone spur only to wind up in severe pain for months, unable to work or pursue normal activities over that time frame. While these scenarios may be unusual, they are certainly more common than we would like.