Shockwave therapy for tendons - an expensive placebo or a valid adjunct to treatment?

Today we look at one of the treatment options for tendinopathy (not tendonitis!) – Shockwave Therapy (also known as ECSWT = Extracorporeal Shockwave Therapy).

Shockwave Therapy is a machine that fires an ‘acoustic pulse’ – basically a dense sound wave – into the tendon, with the idea of reducing pain an perhaps stimulating some sort of ‘healing response’ in the abnormal tendon

 

A shockwave machine looks something like this (image from prpinjection.blogspot.com)

A shockwave machine looks something like this (image from prpinjection.blogspot.com)

And the 'gun' on the shockwave machine looks like this (from prpinjection.blogspot.com)

And the 'gun' on the shockwave machine looks like this (from prpinjection.blogspot.com)

 

This forms one of the ‘passive’ treatment options for tendons, which includes other interventions such as blood injections (PRP, or Platelet Rich Plasma, or ABI, Autologous Blood Injection), other injections (Corticosteroid, a sclerosing agent such as Polydocinol), massage, dry needling, interferential, ice and heat therapy…. the list goes on.  Perhaps a topic for another day, but most of these passive treatment options have either been proven ineffectual or have limited research supporting them.

(PRP in particular has come under a lot of criticism with no high level research supporting it and some vocal criticism highlighting evidence against PRP!)

PRP was (is!) considered a panacea for tendon pain (and several other conditions) by some. The research at this stage doesn't support this!

PRP was (is!) considered a panacea for tendon pain (and several other conditions) by some. The research at this stage doesn't support this!

In Australian physiotherapy circles at least, most of the rehabilitation for tendinopathy is based around a loading (or structured strength) program.  I agree – and this forms perhaps 80-90% of the treatment advice I provide during a consultation.

 

So back to Shockwave Therapy – is it an anomaly from the above list and does it provide a real treatment benefit? Shockwave Therapy was derived from lithotripsy, which is a medical procedure used to destruct calcifications such as kidney stones. Based off this it has been suggested that Shockwave Therapy would be helpful for the tendon injuries that involve calcific deposits.  This of course assumes that the calcific deposits in tendons are a contributor to the pain and again this hasn’t been demonstrated with research that I am aware of.

Regardless, it can be quite expensive, with clinics charging up to $120 for a session (lasting 5-10 minutes) and 3-5 sessions recommended (about 5-8 days apart).

 

An article from the Equine Veterinary Journal (of course!!) from 2009 (http://www.ncbi.nlm.nih.gov/pubmed/19562893) has suggested at the potential mechanism of Shockwave Therapy.

In this study, the researchers used 6 ponies with ‘normal’ tendons. The ponies were treated with shockwave (600 shocks, we often use 2400-3000 but at various intensities) on two locations (one tendon and one ligament interestingly), and then 6 weeks later treated on two separate tendons. Three hours later they were euthanised (you can see why the study was on horses now!) and their tendons examined.

Before we go onto results, it’s important to know what a ‘normal’ tendon looks like. A normal tendon is largely composed of overlapping filaments of collagen, which are like the building blocks of tendon tissues. These overlap a bit like long bricks in a wall. It’s a bit more complicated than that, with several other structures comprising a tendon, and multiple types of collagen, but that’s enough for the purpose of this article).

This is a picture of a normal tendon (taken from the Bosch paper) where you can see the collagen layout.

This is a picture of a normal tendon (taken from the Bosch paper) where you can see the collagen layout.

 

So, what happened after the shockwave? The researchers had the benefit of seeing tendons that had very recent (3 hours) and more distant (6 weeks ago) shockwave therapy.

 

At 3 hours, there were very significant changes! The tendon had lost its normal ‘bricks in a wall’ type pattern (more so at 3 hours than 6 weeks. 

There was a significant increase in the amount of degraded collagen at 3 hours, and a significant decrease in degraded collagen (both compared to the opposite, control leg of the ponies) at 6 weeks.

The researchers also measured gene expression levels for a substance that indicates collagen disruption (called MMP3) and also one that indicates collagen remodeling (MMP14).

At 3 hours after shockwave, there was a significant down regulation of MMP3 at 3 hours, and a significant up regulation of MMP14 at 6 weeks. This, on the surface, appears to correlate with the visual (histological) findings of collagen disruption at 3 hours and collagen ‘healing’ at 6 weeks.

So, although these studies are on healthy tendons (not pathological tendons), there is certainly some evidence to suggest that shockwave a) causes some initial disruption of the tendon matrix, and b) some reformation of the tendon matrix.  What hasn’t been shown in this article is if shockwave has a positive effect on pathological (unhealthy) tendons.

Also, what we need to remember from this article is that the positive effects of shockwave take around six weeks to work (assuming that a healthier looking tendon on histological examination correlates to less pain, which is certainly at least a partial assumption).  It is probably wise too to suggest that patients rest from exercise (particularly those involving high tendon loads such as running, jumping etc.) for at least a day or so after shockwave treatment while the initial (likely cellular or biochemical) reaction to the shockwave treatment.

Interestingly, when using shockwave at the clinic we often see an immediate pain improvement, this is often quite significant (30-50% pain reduction or more). I’m sure this is too much to be placebo! It’s hypothesised that the shockwave acts somehow to immediately reduce the pain from the tendon. Tendon pain is still not that well understood – this is currently the subject of quite a lot of research!  Perhaps the pain reduction is due to introducing a second painful stimulus – shockwave is quite uncomfortable – in a similar way to how acupuncture can give short term pain relief.

So, take home messages

1.      Shockwave may be a useful adjunct to treating chronic tendinopathies.

2.      Full effects of shockwave may take up to six weeks

3.      It’s prudent to ‘take it easy’ for a day or so after shockwave

4.      The shockwave can have an immediate pain reducing effect which allows the patient to do more rehab (more my interpretation of anecdotal treatment here.

Thanks to Ebonie Rio (@tendonpain on Twitter) for the link to the article and Jill Cook (@ProfJillCook) for her ongoing thought provoking research and discussions on tendon.

I'm on Twitter @aidanrich - Google + here and LinkedIn here

(cover image from www.sport-injury-info.com)