Update 2/2016 - the obscure relationship between strength, movement and injury (and more)

Dear all

Some great stuff in tendinopathy blog 2. First ainvestigating hip abduction strength in gluteal tendinopathy - provokes thought around the obscure relationship between strength, movement and injury. Then a focus on some new injections studies.

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All the best for now

Peter

This is an interesting study by Allison et al. investigating hip abductor strength in 50 individuals with unilateral gluteal tendinopathy and 50 sex and age matched controls. Strength testing was performed in supine with a hand held dynamometer. The test limb was in mid range rotation and 10 degrees abduction – as you can see in the figure below 2 fixation belts were used. No participants experienced pain during testing. They found that there were deficits in the symptomatic hip (32%) and asymptomatic hip (23%) compared with controls. There was also an 11% deficit in the symptomatic compared to asymptomatic hip of the gluteal tendinopathy group. This is consistent with Heales 2014 systematic review findings of bilateral motor changes among people with unilateral tendinopathy and it is likely they are at least partly centrally mediated. Key implications are 1) hip abductor strengthening should be considered for gluteal tendinopathy patients (as is commonplace); 2) we can’t rely on the unaffected side for a strength baseline. The authors propose to valid explanations - the strength deficit may be secondary to injury OR primary and related to dynamic valgus that is proposed as risk factor for gluteal tendinopathy. Strength and dynamic valgus have an obscure relationship, partly because strength is a poor term and may be many things eg reps to failure, isometric max, eccentric/concentric peak torque, 6rm, jump performance, etc. But also partly because poor muscle activation, length-tension issues (poor inner range strength, as suggested by Grimaldi et al.) and other factors like reduced leg stiffness may drive dynamic valgus, foot function, etc, etc, rather than classic ‘strength’ measures like max isometric. For example, a recent study by Esculier et al. found impaired Glut Med activation was related to dynamic knee valgus among females with PFP that had a rearfoot strike, but hip abductor strength (MVIC) was not related. Take home message, it is complex. We need to apply sound clinical reason in the relationship between strength, dynamic valgus and injury, ie 1) is dynamic valgus present- can we reliably assess? is it consistent?; 2) is it relevant? think kinetics ie forces and how excessive the pattern is; 3) can we identify the mechanisms with the clinic limitations of equipment, time, etc (in other words how comprehensive and valid are out strength and function assessments?); 4) can we change the mechanism? ; 5) or can we address simply by adapting to this movement pattern?

Interesting review by Tsikopoulos and co workers from Thessaloniki (a wonderful city in Northern Greece). They asked whether PRP is superior to placebo or dry needling and performed a systematic review with meta-analysis. Five RCT’s were included (2 lateral elbow, 2 rotator cuff, 1 patellar tendon) which is pretty shocking when you consider the number of case series (all showing positive results of course) that have been published on PRP – enough case series I think! They found marginal positive effects favouring PRP at 2, 3 & 6 months but only when looking at the rotator cuff studies as a subgroup. Otherwise, there was no benefit for PRP over placebo or dry needling. This study confirms, at worst, NO EVIDENCE, at best, CONFLICTING EVIDENCE for PRP compared to placebo. There is another study in the Achilles also showing no benefit over placebo (de Vos 2010) but it was excluded as there was no ultrasound confirmation of diagnosis (a bit harsh but does not really change the story). So should we use PRP clinically? The reason is it popular is that although the evidence is poor there are not really any alternatives that may not be harmful, although high volume saline injections without the potentially harmful steroid may be up and coming - read on…

Another injection study next up…Prof Nicola Maffulli et al (one of the hardest working tendon researchers I know), have added to the literature around high volume imaging guided injections. I have included this cool video of the technique, from Dr Otto Chan, a radiologist who first developed the technique with colleagues in London (it is of the Achilles (sagittal plane), but you can clearly see the fluid entering and ‘stripping’ deeper fatty away from the tendon). The injection is usually a cocktail of 1) a large volume of saline, 2) local anaesthetic, 3) steroid. There may be a mechanical ‘stripping’ effect or biochemical effect (of course the latter is very likely with steroid). RCT’s have been lacking so far. This study unfortunately is another case series, but has the longest follow up time to date. They use aprotonin instead of steroid, and patients had between 1-3 injections 2 weeks apart (mean 1.8) – the injections were repeated if symptoms and neovascularity were present 2 weeks post injection. There was a significant improvement in VISA and VAS scores at 15 months and 72% returned to their prior level of sport. This study adds to case series evidence (level 4 evidence) showing HVI may be beneficial in patellar tendinopathy – what we need is RCT’s with placebo control, including a HVI arm without steroid or aprotonin (the issue with aprotonin is that there have been negative effects reported and it is not licensed for use anymore in some countries). I know there are groups working on the holy grail RCT as we spoke, so hopefully more answers soon!

High Volume Injection Achilles from Peter Malliaras on Vimeo.

Vimeo

High Volume Injection Achilles from Peter Malliaras on Vimeo.

We continue with the medications and injections theme. This systematic review, again by Maffulli et al., included only RCT’s investigating local pharmacological treatments in Achilles tendinopathy. They rated study quality with the Coleman methodology score, and the range was 61-80/90, which is relatively high. The figure below shoes all the pharmacological agents investigated and the number of comparisons (and sample size in brackets). You can clearly see the huge number of drugs tested, but aside from PRP and autologous blood only 1 study made these comparisons in each case. Only Polidocinol showed promising results, and this was only in 1 RCT. A subsequent retrospective study failed to find positive results (van Sterkenburg 2010). There were reported short but not long term term benefit for prolotherapy, and short term benefit for skin derived fibroblasts. There were no benefits over placebo (PRP) or conflicting findings (autologous blood) reported for blood products. The very important take home message is that, at this stage, there is no strong evidence supporting the use of any local pharmacological agent in treating Achilles tendinopathy. I think a good note to end our discussion of injections.