Human Amniotic Membrane Injections for Plantar Fasciitis
When I first read about using placenta tissue to treat plantar fasciitis, I thought whaaat!? Are we getting that desperate to find a better way to treat plantar fasciitis? Who would be interested in this treatment? And how does it work? After reading more around the history of its use in medicine which dates back to the early 20th century where it was used to treat wounds and burns, I became intrigued to know more. This article reviews the use of amniotic membrane injections for plantar fasciitis.
What is Human Amniotic membrane?
Human amniotic membrane is a reproductive tissue composed of amnion and chorion. The amniotic membrane is formed after conception during the fetal maturation process. Amnion serves as the principle tissue separation between mother and child during pregnancy. The recovery of the placenta does not affect the baby or the delivery process. All donors are tested for infectious diseases, similar to the testing done for blood donation, and additional sterility testing is performed once the tissue has been processed.
Amniotic membrane in its native form has inherent properties that enhance the healing process. These properties include being immunoprivileged, modulating inflammation and reducing scar tissue formation. It is also recognized that amniotic membrane is a reservoir of multiple growth factors involved with tissue growth and regeneration. For these reasons amniotic membrane has been used for its therapeutic potential for wound healing, tissue repair, and regenerative therapy.
As amniotic membrane injections are a new form of treatment for plantar fasciitis, there currently isn't much evidence to prove its efficacy. Nonetheless, there are a few studies that have investigated this.
A study in 2013 by Zelen and colleagues (2013) compared amniotic membrane injections with placebo. In total there were 45 people included in the study. and participants were randomised into 1 of 3 groups with 15 in each group.
group 1 - local anaesthetic injection followed by an injection of saline (sterile water)
group 2 - local anaesthetic injection followed by an injection of 0.5 cc of amniotic membrane (small dose)
group 3 - local anaesthetic injection followed by an injection of 1.25cc amniotic membrane (larger dose)
The participants were reviewed on a weekly basis for 8 weeks. The table below demonstrates the group average amount of change in their reported pain scores week on week. As displayed, there is a significant difference between the placebo group level of improved compared with the two other groups that received the amniotic membrane injection.
(Zelen et al 2013)
There are a few drawbacks with this study. The authors received financial support from the company that produces the amniotic membrane product which increases bias. Participants in each group were all issued a night splint and orthotics in addition to receiving an injection. The study findings are limited to a short term follow up of just 8 weeks. It is not known whether the participants continued to get better or whether their symptoms recurred in the long term.
Another study compared amniotic membrane injections with steroid injections (Hanselman et al 2014). This study was a double blind randomised controlled trial, which means neither the researchers or the participants knew which type injection each participant received. This helps to reduce bias. There were 21 participants included in the study separated into two groups:
Group 1 - steroid injection = 14 participants
Group 2 - amniotic membrane injection = 7 participants
Participants were asked to grade their level of improvement (0% = no improvement 100% = fully resolved) at 6 weeks and 12 weeks post injection. At the 6 week follow up the steroid group outperformed the amniotic membrane group with an average improvement of 81% vs 65% respectively, however at the 12 week follow up the amniotic membrane group outperformed the steroid group with an average improvement of 87% vs 60%.
The most recent study compared amniotic membrane injections to saline (sterile water) injections in patients diagnosed with plantar fasciitis (Cazzell et al 2018). This was a level 1 study meaning that it was a high quality study. There were 145 patients randomly divided into 2 groups:
73 patients in the amniotic membrane injection group
72 patients in the placebo group
Prior to treatment, both groups were asked to score their pain using the visual analogue scale (VAS). Patients scored their pain from 0 (no pain up to 100 (worst imaginable pain). The amniotic membrane group scored their pain as an average of 71/100 which reduced to 17/100 at 3 months after receiving treatment. The placebo group scored their pain as an average of 70/100 which reduced at 3 months to 38/100. These findings demonstrate a significant difference between the two groups with the amniotic membrane injections proving to be more effective than placebo. One thing to point out is that in addition to receiving injections, both groups were also issued with a night splint as treatment. This of course, could have provided additional pain relief which makes it difficult to determine how much of the improvement was due to the injection alone. Another drawback from this study is that similar to the previous study by Zelen and colleagues, the authors of this study also received financial support for the research, authorship, and publication. This increases the possibility of bias due to a conflict of interest.
The concept of using amniotic membrane injections as a form of regenerative medicine in plantar fasciitis is both novel and exciting. Currently there are just 3 studies investigating the efficacy of these injections. All 3 of these studies are were RCT's which help strengthen the quality of the findings, however all 3 studies are not without their limitations. For example they were all funded by the producers of the amniotic membrane products. In my humble opinion, this early evidence supports the use of amniotic membrane injections for plantar fasciitis as all 3 studies demonstrated significant improvements across various outcome measures. An additional positive is the safety of the treatment with no negative side effects on the health of the plantar fascia tissue, unlike steroid injections. Also amniotic membrane injections are believed to help with the degenerative process involved in plantar fasciitis. As our knowledge around the underlying disease process of plantar fasciitis continues to improve, more and more treatments aimed at treating the degenerative process are becoming more readily available for example, shockwave therapy and PRP injections. Amniotic membrane injections may be another that we can add to the list.
Thanks for reading. Comments welcome.