Are isometrics helpful for lateral elbow tendinopathy? The answer may surprise you

Hi all,

Welcome to the tendinopathy blog 9 for 2016 – the year is flying!

Enjoyed lecturing post grad podiatrists and physios this week – it was a new tendon lecture where I argue for a minimum viable management approach in tendinopathy. Will post a recording to subscribers soon. Subscribe via the homepage if you would like to see it.

A review of three new tendinopathy studies this week – isometric in lateral elbow tendinopathy, a new Achilles rehab study and a PRP study – with some interesting findings and clinical messages.

Hope you enjoy

Peter

First up is a very interesting study from Brooke Coombes and team at UQ.

What they did: They took a group of patients with lateral elbow tendinopathy (n=24, 13 men, 11 women) and performed a blinded repeated measures study. There were 3 comparison arms: 1= isometric wrist extension at 120% of pain threshold (10x15seconds); 2= isometric wrist extension at 80% of pain threshold (10x15seconds); 3= control group (they just sat there doing nothing for the same amount of time). Participants reported greater pain during the 120% vs 80% of pain threshold exercise. There was a minimum washout period of 48 hours between interventions. A dynamometer was used to ensure the appropriate force was maintained during the isometric exercise – see figure below. The order of interventions was randomised. A blinded researcher assessed pain free grip strength (dynamometer), pressure pain threshold (pressure algometer) and pain intensity (NRS) before, immediately after and 30 minutes after each intervention.

What they found: The main finding was that after the 120% of pain threshold exercise (‘supra-threshold exercise’) there was an increase in resting pain intensity immediately and at 30 minutes. There was no change in pain free grip or pressure pain threshold on either the affected or unaffected arm. This is certainly different to the pain inhibitory effects of isometrics in normal participants (known as exercise induced hypoalgesia (EIH)). Put simply, exercise, particularly isometric, has been shown to reduce experimentally induced pain (eg pressure pain threshold) for 15-30 minutes in normal people, and because it occurs at the exercised parts as well as others parts, it is probably related to central pain changes such as greater descending inhibition (Naugle 2012). Chronic pain patients seem to have an impaired EIH response – sometimes blunted or even hyperalgesic (Lannersten 2010 – in this study they looked at localised ‘myalgia’ and fibromyalgia patients). This may explain the findings in the Coombes study, ie the nervous system is wound up and instead of inhibition you get more pain with exercise. Fear, expectation and perceived pain intensity and disability may influence pain inhibition in chronic pain patients (self reported pain/disability and kinesiophobia correlated with pain during contraction in the Coombes study – see graphs below). Of course we cannot rule out an effect on local nociceptors following the isometrics (maybe tendon compression contributed to this?).

Clinical interpretation: This study indicates that the short term response to isometrics may be nothing at all (ie pain with loading-painfree grip) or negative (rest pain) in lateral elbow tendinopathy. This is different to Rio et al. 2015 who show reduced pain with single leg decline squat loading in patellar tendon following isometrics. I think the isometrics were performed with minimal or no pain (I could be wrong) so maybe even in the patellar tendon they would lead to more pain if performed suprapain threshold as in the Coombes study. Maybe the elbow is different, such as 1) greater fear/expectation of pain with load (general we see a less clear ‘warm up’ phenomenon (ie improved pain with exercise) in the elbow vs patellar tendon) or 2) different pain mechanisms given they had lingering rest pain after load in the Coombes study after exercise, which is rare in patellar tendinopathy. Remember these papers and blog focus on short term effects of isometrics on pain, long term effects are a different story.

A sensible message seems to be; address/consider fear and expectations carefully, and load very cautiously initially to gauge response. Would love to hear others interpretations and thoughts too.

This study by Vaegter 2015 is relevant and worth mentioning here (thanks to the PT Inquest podcast where I first heard about it - definitely worth a listen. Hosted by Eric Meira @erikmeira and JW Matheson @EIPConsult). In the study they divided 61 chronic pain patients (including some with lateral elbow tendinopathy) into two groups based on pressure pain thresholds (lower pain thresholds=higher pain sensitivity). The main finding was EIH was partly impaired in the group with higher pain sensitivity. This suggests we may need to modify exercise in people with higher pain sensitivity.

Second we have a study by McCormack et al. out of Rocky Mountain University of Health Professions and Indiana

What they did: These authors have performed a randomised controlled trial comparing eccentrics with eccentrics + Astym in the management of Achilles tendinopathy. They focused on the insertional because the current literature suggests it is more difficult to manage. The eccentrics were your typical 3 sets of 15 for 12 weeks. The Astym group was seen an additional twice per week for 12 visits for a 20-30 minute Astym treatment – as I know nothing about Astym here is how they describe it – ‘During each treatment session, a progression of instruments with decreasing areas of surface contact was used (see figure of instruments below – they don’t look that nasty). They tried to control for regular contact in the Astym group by phoning the control group was weekly to see how they were progressing.

What they found: There were 9 participants in the eccentric only and 7 in the Astym group. As expected VISA improved at short and long term, but the really interesting thing was that the Astym group had a significantly greater VISA change at pretty much every outcome point i.e. 4, 8, 12, 26, 52 weeks (despite the very small numbers) – see the graph below. Numeric pain rating also improved but was not significantly different between groups at any timepoint.

Clinical interpretation: On the surface this seems like a very positive result for a manual adjunct, in this case instrumented tissue manipulation. Possible mechanisms that are discussed in regards to Astym are regeneration and remodelling of soft tissue, in other words a cellular anabolic effect but there is little evidence to support this in humans, and an effect on the nervous system and pain would seem the most likely. The huge obvious issue with this study is a lack of adequate placebo control. The closer physical contact with the therapist in the Astym group may have influenced fear, motivation, confidence, compliance, encouragement, etc. So it is very hard to overlook this bias.

Lastly onto a very common but dividing treatment in tendinopathy: platelet rich plasma (PRP). Or platelet rich placebo as some people refer to it. A recent study by Kaux et al. took a slightly different approach. They investigated the effect of 1 PRP injections versus a closely followed second injection. In a well designed randomised controlled trial they found that there was no benefit to adding the second injection. See the graph below which shoes a similar change in VISA-P (pain and function) over the twelve month follow up in both groups. The black line is the group that had only 1 injection and you can see that they appear to have a better short term benefit although it was reported as not significant. All participants performed an eccentric decline squat program but there was no exercise only group - probably because all patients had previously failed classic treatments including rehab.

Clinical interpretation: PRP involves spinning blood to concentrate platelets and growth factors that are thought to have a healing effect when injected into tendon. We know, however, that PRP does not appear to contribute to improved tendon structure over and above rehab (de Vos 2011) and what the PRP may simply do is cause short term cellular response (Lane 2013). We also know that remodelling of tendon requires loading. As with many treatments, case studies show that it is a wonder drug, whereas RCT show it may have little effect over placebo (Tsirkopoulos 2016). Despite this it is still very popular clinically and that is because other options are either harmful or associated with poor long term outcomes (steroid) or, as with PRP, also not evidence based. The big argument from the supporters of PRP is trials do not show the effect because we are not doing it properly – i.e. platelet concentrations vary, too many leukocytes that may impair healing, not the right number of injections etc. This study answers some of that criticism and suggests 2 injections is not better than 1 – but I guess the search for the perfect potion and delivery will continue!

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Keep joining the dots

Peter