The Research Behind Shock Wave Therapy

In the last few months, shock wave therapy (ESWT, or extracorporeal shock wave therapy) has come up in multiple platforms and conversations. Are you using shock wave or referring patients for shockwave therapy? Perhaps you’re considering it but feel you don’t yet have enough information? Onlinepethealth has done two Research Refresh summaries on this modality, including the effect of extracorporeal shock wave therapy (ESWT) on supraspinatus and infraspinatus injury on our small animal platform, and the effect of ESWT on back pain on the equine platform.

Several papers have been written on the modality, revealing valuable information on its mechanism of action and effects.  Here are the important take-away points from six papers on ESWT. The first two appeared in our Research Refresh series:  

3 take-home points for pain in the equine back

Trager et al., 2019, examined different pathologies in the equine spine, specifically in the thoracic and lumbar areas. They performed three treatments of ESWT at two-week intervals, measuring pain at set time points throughout the period and beyond. They concluded the following:

1. Shock wave will provide pain relief in the equine with back pain and pathology.
2. Horses may need fewer treatments in the thoracic area than in the lumbar area, as the thoracic area responded to ESWT after one treatment, while the lumbar area required three treatments.
3. Shock wave treatment should be accompanied by a rehab plan to address the other goals of rehab, such as strengthening spinal stabilisers and improving posture and mobility.

3 take-home points for treatment of the canine supraspinatus and infraspinatus

I learnt so much about the conditions of supraspinatus and infraspinatus while working on this Research Refresh, that I wrote a blog focusing on these conditions. Leeman et al., 2016, performed a retrospective study and evaluated several aspects of these conditions, comparing dogs that received ESWT treatment only with dogs that received ESWT together with a therapeutic exercise programme. They concluded the following:

1. 75% of dogs no longer needed pain medication at the end of the study period.
2. The best outcomes were reported in moderate and severe cases.
3. There was no difference in results between the group receiving only ESWT and those receiving ESWT together with therapeutic exercise.

For more details on those two papers, head over to the equine and small animals members’ portals, and find the recordings in the Research Refresh library.

I have recently read two more papers that highlight some interesting points with regard to the use of this modality in practice. Let’s take a look at some of the take-home points from each:

Extracorporeal shockwave therapy improves short-term limb use after canine tibial plateau levelling osteotomy (TPLO)

Barnes et al., 2019, compared cranial cruciate ligament ruptures (CCLR) in dogs treated with TPLO only with dogs treated with both TPLO and ESWT. The results were as follows:

1. Weight bearing increased faster amongst dogs treated with ESWT.
2. There was no difference between the two groups when it came to the occurrence of post-op complications.
3. There was no difference in many of the outcome measures, including stifle circumference, goniometry measurements, and subjective pain scores at all evaluated time points.
4. Ground reaction force values improved in the ESWT treatment group, and decreased in the group with TPLO only at the two-week mark.
5. At the two-week mark, the TPLO group had a reduced ground reaction force, while the ESWT group had an improved GRF compared to the pre-operative level.

So, very interestingly, ESWT impacted the amount of weight bearing in a positive manner, but had no impact on the other outcome measures. It is possible that the pain-relieving effect of ESWT enabled the dogs to increase their weight bearing in the first two weeks post-op. As the research on equine back pain concluded, it is necessary to include other therapeutic modalities in order to address and improve other specific outcomes, such as stifle circumference.

Review of the application and efficacy of extracorporeal shock wave therapy in equine tendon and ligament injuries

Yocom et al., 2019, performed a literature review covering research on several aspects of ESWT; the underlying physics of the modality, the molecular changes, the combination of ESWT with regenerative medicine, safety aspects, analgesia, equipment needed, specific soft tissue injuries including suspensory ligament desmitis, superficial digital flexor tendonitis, accessory ligament of the DDFT, and back pain. It also makes further literature recommendations.

As you can see, this is a comprehensive paper yielding many valuable points. Take-home points for me were the following:  

1. ESWT treatment for soft tissue injuries in horses does have healing effects and provides pain relief.
2. When it comes to proximal suspensory injuries, ESWT can aid in returning horses to sport faster, and filling in defects in the tendon sooner.
3. For a superficial digital flexor tendinopathy, ESWT may help to fill in the defect faster, but whether or not there is an effect on the lameness score or a faster return to function is still inconclusive.
4. ESWT does provide pain relief for back pain. In many studies ESWT is combined with other therapies, and so the true effect of ESWT is not clear.
5. Specific treatment protocols still need to be validated.

Other research

Two other research papers are worth mentioning here. Kieves et al., 2015, studied the effect of shockwave therapy on bone healing, concluding that electro-hydraulic ESWT applied post-osteotomy improved bone healing at the 8-week mark.

Jessica Dahlberg’s thesis is especially interesting. She assessed the efficacy of ESWT on osteoarthritis and analgesia in animal models, and discusses the modality in its various forms in detail, including the in-vitro and in-vivo effects on bone, tendons, ligaments, joints and other areas. She also discusses findings specific to pain relief, the mechanisms by which pain relief is achieved, and the duration for which it is achieved. In this regard she says:

Numerous hypotheses have been proposed as to the mode of analgesic action induced by ESWT. None, however, have been truly proven. The presence of anesthesia after ESWT in horses has not yet been defined. The importance of this data applies to both horse and rider, as risks may be involved if pain comprehension by the horse is absent during performance. Regulations based on empirical data have been implemented in multiple horse racing jurisdictions due to these dangers. Therefore, further objective evaluations of the analgesic period following ESWT in horses are needed in the literature. The main objective of the manuscript in Chapter 4 is to measure the duration of acute analgesia following a single session of ESWT in horses with naturally occurring unilateral forelimb lameness.

A valuable tool for our toolbox

It seems clear that ESWT is a valuable tool for our toolbox, but that we still lack much information on specific treatment protocols for different conditions, and on the therapeutic effects on specific tissues. It is important to know how ESWT combines with other modalities such as therapeutic exercise and manual therapy, as well as regenerative medicine. Whether the effect is to provide pain relief or to improve healing in specific tissues, ESWT clearly has a positive effect on canine CCLR and supraspinatus and infraspinatus injuries, on bone healing and on equine back pain and ligament and tendon injuries.  We can certainly include ESWT as a part of our multimodal approach to treating challenging (and maybe not so challenging) pathologies in both canine and equine cases.

What device?

In most of the research showing positive outcomes, an electro hydraulic device was used. It is important to familiarise ourselves with the various kinds of shock wave devices available and their levels of proven efficacy before either purchasing a device or referring to a practitioner who uses a particular device. Pulsevet have a great article that covers the range of shock wave therapy devices available.

I would love to hear your take on this modality. How are you using it, if at all? If you’re not using it, is that decision based on your lack of access to the modality, or do you have a clinical reason for excluding it from your toolbox? I would love your feedback and thoughts!