Welcome to tendinopathy blog 14.
Here is a link to the new Modern Tendinopathy Management Lecture if you have not seen it already. 1 Hour of free content!
This week we look in detail at a biomechanical study investigating Achilles tendon load at different midportion and enthesis sites, with some very useful clinical implications. Then we examine an Achilles tendinopathy evidence translation tool and also consider how useful these tools really are, and what they tend to leave out.
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Non uniform Achilles load and why all roads lead to the seated calf raise What they did: There has been lots of interest recently in non-uniform loading of the Achilles tendon (AT) and whether this relates to injury. Here is a brief run down of key points. Strain in the soleus and gastroc has been shown to be non uniform, for example in walking there is greater superficial tendon strain (Franz 2015). This may be related simply to different moment arms, but also independent soleus and gastroc muscle function. For example, Ishikawa 2005 found eccentric action in soleus and isometric in medial gastroc. Adding to this groups have been able to successfully dissect apart the soleus and gastroc portions of the AT (Szabo 2009, Edama 2015). And recently specialized regions in some tendons ie the intra-fascicular matrix, have been found and they are known to facilitate energy storage but may also facilitate strain gradients in these energy storage tendons (Thorpe 2012), ie allow muscles like soleus and gastroc to work independently.
Hope that clarifies the background! So on with the study…a new one by Toumi et al. - they aimed to investigate whether there was evidence of differential load at the Achilles enthesis by examining the structure of the enthesis, as well as along the tendon using mathematical modelling. They carefully dissected out AT portions from the soleus and gastrocs in 12 cadavers, 6 women & 6 men. Cadavers that had calcaneal spurs seen on X-ray were excluded. They assessed the volume of the soleus and gastrocs and the structure of different parts of the tendon-bone enthesis (bone and fibrocartilage) for morphology that would suggest increased load. Finally, they used a finite element mathematical model to estimate the stress (force/cross-sectional area) throughout the length of the AT.
What they found: The AT is thickest (anteroposterior) in the midportion 3.8-6cm proximal to the calcaneum, but it also has the lowest perimeter distance in this region. This has been shown before in MRI studies. What they have added with the finite element model is that the Achilles tendon stress is greatest in a similar region of the tendon, ie the bit with the least volume or bulk, which makes sense! (4.6-7.9cm above the calcaneum) – see figure below (red = greatest stress).
They also confirm previous findings that the soleus portion of the Achilles tendon re-orientates due to twisting of the tendon – proximally the soleus is deep to gastroc, but distally the soleus ends up medial, the medial gastroc posterolateral and the lateral gastroc anterolateral (similar to findings in the Szabo dissection study seen in the figure below).
They also show that the total calf muscle volume is made of soleus mainly (43.7%), then medial gastroc (34.3%), then lateral gastroc (22.1%). This fits in withthe very high physiological cross sectional area of the soleus (Lieber 2011) and much higher forces (x bodyweight) in the soleus versus the gastroc in running (see table below showing predicted muscle forces in running at increasing speed, adapted from Dorn 2012) and
Last, but I think the most interesting finding, was that there was greater trabecular volume and fibrocartilage thickness in the medial and central portions of the enthesis. This suggests greater load in these regions.
Clinical interpretation: This study supports the idea that tendinopathy/rupture commonly occurs in the midportion because this bit has the smallest volume and is under greatest stress, not because of poor blood supply (Theobold 2005). Even accepting limitation/assumptions of the model they used, I think this is a key point for clinicians - it certainly gives justification to loading.
The study findings also support prior cadaver dissection findings that the medial Achilles enthesis is comprised mainly of tendon originating from the soleus. What they add which is new and interesting is that the medial enthesis seems to be under greater load when you consider bone volume and fibrocartilage thickness. Although this is not where we always see pathology/pain – in my experience it can be medial or lateral side enthesis pain and some have diffuse pain. Many factors may explain this, such as sensitization, or individual biomechanics (e.g. foot kinematics) or anatomy (e.g. Haglunds bumps).
For me the best message from this study and a good point to finish on is a reminder that soleus is a powerhouse, and we must address it in Achilles rehab. Check out Seth O’Neills blog which expands on the role of soleus. His research also highlights soleus functional deficits in Achilles tendinopathy. Below is a slide of patients doing seated calf raise in various ways, a great exercise for soleus!! (PS even though the slide shows double leg, always go for single leg!) Listen to my new 1 hour Modern tendinopathy management lecture to hear their stories!
What is best practice for Achilles tendinopathy? What they did: This study by Ezzat et al. examined the use of the Achilles tendinopathy ‘toolkit’ (ATT) by physiotherapists in British Columbia. It caught my interest mainly to raise awareness of the toolkit. A ‘toolkit’ is a common knowledge synthesis tool that is defined as ‘the packaging of multiple resources that codify explicit knowledge, such as templates, pocket cards, guidelines, algorithms, summaries, and that are geared to share knowledge, educate, and/or facilitate behavior change’ (Barac 2014). Clinicians are able to decide which of the ‘translated’ evidence in the toolkit they use for an individual patient, rather than having a recipe. The ATT is freely available and includes a treatment algorithm and evidence summary for physical therapy interventions – you can check it out here (see screenshot below).
The authors of this study were interested in physios perceptions of the ATT, and whether it influenced best practice in managing Achilles tendinopathy. Members of the Physiotherapy Association of British Columbia were emailed a survey. The 28 question survey included demographic info, exposure, awareness, perceptions, usability and applicability to clinical practice of the ATT, as well as the physios knowledge, attitudes and a clinical case scenario that allowed them apply their knowledge.
What they they found: The response rate was close to 10% (pretty low) when considering those that completed the full survey and they were representative of the population, although slightly younger. Of the respondents, 81% had heard of the ATT, and 53% had explored the toolkit and most had positive perception – eg they agreed the toolkit provided enough information to treat an Achilles patient. In regards to improving the ATT, participants suggested additional treatment strategies – which suggests clinicians do not feel they have enough options, or are not able to apply what they have adequately. Participants who had explored the ATT were 2.8 times more likely to follow ‘best practice’ recommendations when answering the clinical scenario. Physios that were above 50 and had been practicing for more than 20 years were less likely to follow ‘best practice’ recommendations.
Clinical interpretation: The main finding of this study was that physios exposed to the ATT were more likely to follow ‘best practice’ recommendations. This is real positive reinforcement of knowledge translation tools like this. But there are limitations...
The key message from the ATT is the only thing we can really be sure about is exercise, so this must be in your treatment plan for Achilles tendinopathy patients. In my opinion the other key factors are education and load modification, but these do not come across in the research so are not highlighted in the ATT. Education on pathology and pain, as well as setting patient expectations of time frames, response to exercise, addressing cognitive-emotional factors such as fear avoidance/beliefs, etc, etc are so critical, they can often be the difference between success and failure. What is also lacking is principles of how to apply and monitor rehab. I strongly believe that we often go wrong by following set exercise programs rather than understanding (the actually quite simple) principles that allow us to individualise rehab on a daily basis. Again, check out the Modern Tendinopathy Lecture for details of all this.
Aside from exercises, evidence for the remaining interventions in the ATT is either lacking or limited or conflicting – welcome to the world of physical therapy! You could make arguments either way for most. You can argue manual therapy, orthotics, tape, heel wedges, needling, ESWT have biological plausibility because they often have an immediate effect on pain. Whereas interventions like ultrasound and low level laser therapy (LLLT) I would discourage (LLLT is encouraged in the ATT) because they are based on tissue healing/mechanisms which we have little biological evidence for. In the end these are all adjuncts to be used alongside exercise and what you decide to use will be shaped by patient expectations and preferences, as well as resources and skills of the clinician.
Over and out until next time..
Keep joining the dots people, and keep enjoying your tendons!
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