I have to be honest and admit that the use of platelet rich plasma (PRP) for plantar fasciitis is something that I have had no more than a superficial interest in. I pretty much scanned the abstracts of the studies and systematic reviews as they are published of it in this thread and the one comparing it to other interventions on Podiatry Arena. I also note comments in social media on it from those whose views I respect. From my superficial understanding, it works, it does not work, it works, it does not work … a lot of the studies that compare it to other treatments do not do the “other” treatment very well (ie wrong dosing), which can easily bias the study to PRP being better. Some of the comments in social media from people who I consider real experts, especially in the context of tendinopathy are that it does not work, yet a lot of people claim it does. Yes, I know that the “plantar fasica” is not a “tendon” and it may or may not be appropriate to translate “tendinopathy” research to “plantar fasciitis” (not that this stops people doing so or not doing so if the research on it matches their pre-conceived biases!).
I do note that the most recent meta-analysis of PRP concludes that it is as effective as other interventions. I do note when I glance at most of the studies that do get included in the systematic reviews and meta-analyses that there does appear to be some methodological issue with almost all of them, so how much weight should be given to them?
Anyway, as you can see, I really do not know much about PRP for plantar fasciitis except for that superficial understanding of the evidence and listening to those whose views I normally respect. However, my interest in PRP picked up a week ago when at the AAPSM meeting in San Francisco in which there was a presentation on the topic.
I stand to be corrected and have not verified this by searching the literature, but he said two things in the presentation that I think I interpreted correctly that really got me interested:
1) Local anaesthetic deactivates the PRP. What this means is that if a lot of local was infiltrated in the area vs just a small superficial amount prior to the PRP injection then this may affect the clinical effectiveness of the PRP. Of more importance, if a lot of local was used in a study of PRP, then that would bias the study in the direction of the PRP not being effective. That study is unlikely to be excluded from a meta-analysis or systematic review if all the other methodological issues are sound (ie sample size, blinding etc).
2) The effectiveness of PRP in tendons (he did not mention this in the context of the plantar fascia) might depend on the leucocyte concentration in the PRP. I have not checked the literature on this, but I think he said the PRP works in tendons if the leucocyte concentration is high and does not work in tendons if the leucocyte concentration is low. If this is correct, then it is easy to see how a study could be biased against it working if the leukocyte concentration is low. Those low leucocyte concentration studies will be included the in the meta-analyses and biases them in the direction of PRP not being effective for tendons.
Again, I no expert (or even have a little knowledge) in this and I only superficially aware of the literature in this, but even I can see the issues here. The use of small vs high amounts of local before injecting the PRP and the effectiveness of high vs low concentration of leukocytes in the PRP are issues that need to be resolved and potentially could have huge impacts on the results of individual studies, systematic reviews and meta-analyses; and, more importantly, policy recommendations and clinical guidelines that grow out of that. I see this as a serious problem.
It may well be that if studies are repeated on the local anaesthetic dose and the leucocyte concentration that it does not affect the outcome and then will not bias the systematic reviews and meta-analyses. It is, however, an issue that should be resolved.
Does PRP work for plantar fasciitis? My conclusion is that we do not yet know.
Does this sound familiar? Its the same issues I wrote about on foot orthotic dosing … or am I just being biased or using the logical fallacy of ‘special pleading’?
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