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Influence of the setting: frequency

Most clinical studies have been conducted with a frequency ranging from 6 to 10 Hz. Recent studies now use a frequency ranging from 10 to 15Hz. The influence of the frequency has not yet been clinically assessed except for its influence on treatment duration.
The trend is to treat tendinopathies with a frequency in the range of 10 to 12Hz, enthesiopathies with a frequency in the range of 12 to 15Hz, and muscle with a frequency in the range of 12 to 20Hz, depending on the skin surface above the indication and the number of impulses.

Influence of the setting: number of pulses

Schmitz et al. (20152) showed that a good protocol is 2,000 impulses per treatment. Nevertheless, this is for a high energy per pulse, sticking to the painful point. The modern approach to shock wave treatment tends to increase the number of impulses to 2,500-4,000 depending on the skin surface above the indication to be treated, and moving around the painful spot.

References:
2) Schmitz C, Császár NB, Milz S, Schieker M, Maffulli N, Rompe JD, Furia JP. Efficacy and safety of extracorporeal shock wave therapy for orthopedic conditions: a systematic review on studies listed in the PEDro database. Br Med Bull 2015;116:115-138.

Influence of the setting: applicators

The diameter and therefore the weight of the applicator influence the energy flux density and the cavitation field delivered. As a rule of thumb, the smaller the diameter, the higher the intensity and the smaller the cavitation field. Keep in mind that the maximum energy density is at the tip of the applicator.

Influence of the setting: spring pressure

It is also called the second pressure setting. By gently compressing the spring, you get closer to the pathology spot and thus deliver more energy to the target tissue. In addition, it absorbs part of the refracted wave. Only BTL and EMS have this feature.It is also called the second pressure setting. By gently compressing the spring, you get closer to the pathology spot and thus deliver more energy to the target tissue. In addition, it absorbs part of the refracted wave. Only BTL and EMS have this feature.

Move the handpiece or keep it static?

Most of the clinical studies do not test this parameter by keeping the applicator static on the spot. In terms of energy delivered it is efficient but no so good from the standpoint of patient satisfaction. A good approach is to start away from the most painful spot and gently move toward the most painful spot.

Do we have to try other conservative treatments before using shock wave?

In the early days of ESWT shock waves were considered a “Line 2” or even “Line 3” treatment, i.e., indicated only after application of other conservative treatment protocols without success (for a very prominent example see the “Plantar Heel Pain Treatment Ladder” by Thomas et al., 20103) (Fig. 4 therein). The main reasons for these recommendations were (i) the belief that approximately 80% of all tendinopathies heal within one year without any treatment; (ii) the relatively high costs of ESWT compared to other treatment modalities; (iii) the fact that unlike ESWT, certain treatment modalities (such as cortisone injections) were reimbursed in countries where research on ESWT was performed; and (iv) the possibility to charge the same patient several times for inefficient types of treatment, which was not possible anymore after performing just a few ESWT sessions. However, more recent studies performed in countries with another reimbursement system (China, Korea) have shown that excellent results can be achieved with ESWT on newly diagnosed patients. However, in case the pathology is in the acute phase, it is recommended to wait 1 or 2 weeks in order not to be in the acute phase anymore.

References:
3) Thomas JL, Christensen JC, Kravitz SR, Mendicino RW, Schuberth JM, Vanore JV, Weil LS Sr, Zlotoff HJ, Bouché R, Baker J; American College of Foot and Ankle Surgeons heel pain committee. The diagnosis and treatment of heel pain: a clinical practice guideline-revision 2010. J Foot Ankle Surg. 2010;49:S1-S19.

Although it was originally developed to be used in urology, can it break bones? What about snapping tendons?

No it does not break bones or tendons because the energy density delivered is below 0.6 mJ/mm2 (even with the Power+ handpiece on 4 bar with the 15 mm focus). Breaking of bones with shock waves was shown to occur in experimental studies on dogs with energy flux densities of 5 mJ/mm2.

Should a shock wave treatment hurt?
 

It should not hurt but should be uncomfortable ((VAS score < 7)).

Can I use local anaesthetics with shock waves?

Yes, local anesthetics can be used and are not harmful. However, in case of chronic plantar fasciopathy it was shown in two independent studies that repetitive low-energy ESWT without local anesthesia is more efficient than repetitive low-energy ESWT with local anesthesia (Labek et al., 20054; Rompe et al., 20055). The reason is that local anesthetics block peripheral nerve fibers including C nerve fibers. However, you cannot block C nerve fibers with local anesthetics and activate them with shock waves (Maier et al., 20036) at the same time. Furthermore, the application of local anesthetics limits and may even prevent biofeedback from the patient during treatment.

References:
4) Labek G, Auersperg V, Ziernhöld M, Poulios N, Böhler N. Einfluss von Lokalanasthesie und Energieflussdichte bei niederenergetischer extrakorporaler Stosswellentherapie der chronischen Plantaren Fasziitis – Eine prospektiv-randomisierte klinische Studie. [Influence of local anesthesia and energy level on the clinical outcome of extracorporeal shock wave-treatment of chronic plantar fasciitis] [Article in German]. Z Orthop Ihre Grenzgeb 2005;143:240-246.
5) Rompe JD, Meurer A, Nafe B, Hofmann A, Gerdesmeyer L. Repetitive low-energy shock wave application without local anesthesia is more efficient than repetitive low-energy shock wave application with local anesthesia in the treatment of chronic plantar fasciitis. J Orthop Res 2005;23:931-941.
6) Maier M, Averbeck B, Milz S, Refior HJ, Schmitz C. Substance P and prostaglandin E2 release after shock wave application to the rabbit femur. Clin Orthop Relat Res 2003;406:237-245.

Can I combine ESWT with other conservative types of treatment?

Yes, you can. In case of chronic midportion Achilles tendinopathy, it was shown that the combination of radial ESWT and eccentric loading resulted in a statistically significant improvement in clinical outcome compared to eccentric loading alone (Rompe et al., 20097), radial ESWT being as effective as eccentric loading for this indication (Rompe et al., 20078). The same was shown for the combination of radial ESWT and plantar fascia-specific stretching in case of chronic plantar fasciopathy (Rompe et al., 20159).

References:
7) Rompe JD, Furia JP, Maffulli N. Eccentric loading versus eccentric loading plus shock-wave treatment for midportion Achilles tendinopathy: a randomized controlled trial. Am J Sports Med 2009;37:463-470.
8) Rompe JD, Furia JP, Maffulli N. Eccentric loading compared with shock wave treatment for chronic insertional Achilles tendinopathy. A randomized, controlled trial. J Bone Joint Surg Am 2008;90:52-61.
9) Rompe JD, Furia J, Cacchio A, Schmitz C, Maffulli N. Radial shock wave treatment alone is less efficient than radial shock wave treatment combined with tissue-specific plantar fascia-stretching in patients with chronic plantar heel pain. Int J Surg 2015;24:135-142.