REVIEW ARTICLE |
https://doi.org/10.5005/jp-journals-10040-1274 |
Application of Amniotic Membrane Allograft in the Treatment of Foot and Ankle Pathologies: A Review of the Basic Science and Clinical Evidence
1Department of Orthopedics and Rehabilitation, Tufts Medical Center, Boston, Massachusetts, United States
2Foot & Ankle Research and Innovation Lab (FARIL), Department of Orthopedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States
3Foot and Ankle Service, Department of Orthopedic Surgery, Massachusetts General Hospital, Boston, Massachusetts, United States
4The BIOS Orthopedic Institute, Sacramento, CA, United States
5Department of Orthopedics and Rehabilitation, Tufts Medical Center, Boston, Massachusetts, United States; Boston Sports & Biologics, Wellesley, Massachusetts, United States
Corresponding Author: Walter I Sussman, Department of Orthopedics and Rehabilitation, Tufts Medical Center, Boston, Massachusetts, United States; Boston Sports & Biologics, Wellesley, Massachusetts, United States, Phone: (781) 591-7855, e-mail: walter.sussman@tufts.edu
Received on: 28 August 2022; Accepted on: 26 October 2022; Published on: 31 December 2022
ABSTRACT
Background: In recent years, an increasing number of studies have investigated the use of AM for various orthopedic indications. AM allografts’ anti-inflammatory and anti-scarring properties make them a promising agent used to augment the healing of pathological soft tissue.
Purpose: The purpose of this study is to review the published studies on the use of amniotic membrane (AM)-derived allografts in human subjects for various indications in the foot and ankle.
Results: Studies suggest that when it is used for the treatment of plantar fasciitis, the efficacy of AM-derived products is at least equivocal to corticosteroid injections in the short term and superior to placebo injection in the long term. Fewer studies have investigated the application of AM-derived products in Achilles tendinitis, ankle and foot osteoarthritis (OA), or peripheral nerve pathology.
Conclusion: Additional high-quality supportive data is needed to support the efficacy and safety of AM-derived products in the foot and ankle. Furthermore, clinicians should be aware of the regulatory status of any AM-derived product before its use in clinical practice.
How to cite this article: Nakagawa H, Ashkani-Esfahani S, Waryasz GR, et al. Application of Amniotic Membrane Allograft in the Treatment of Foot and Ankle Pathologies: A Review of the Basic Science and Clinical Evidence. J Foot Ankle Surg (Asia-Pacific) 2023;10(1):13-19.
Source of support: Nil
Conflict of interest: None
Keywords: Amniotic graft, Amniotic membrane, Amniotic mesenchymal stem cells, Achilles tendonitis, Nerve wrap, Osteoarthritis, Plantar fasciitis.
INTRODUCTION
The clinical application of AM tissue dates back over a century ago.1 Since its first use in the early 1900s, AM tissue allografts have been used mainly in the field of wound care and ophthalmology.1-5 Recently, the therapeutic applications of AM tissue allografts have expanded to include a variety of orthopedic indications. This paper provides a review of the structure and function of the placenta and an overview of published studies on the use of AM-derived allografts in human subjects for the treatment of plantar fasciitis, Achilles tendonitis, and OA, as well as its application in peripheral nerve pathology. We will also discuss efficacy, safety, and regulatory concerns.
STRUCTURE AND FUNCTION OF THE PLACENTA
The placenta is a discoid fetal organ that develops during pregnancy and provides an interface between the mother and fetus. The chorionic plate represents the fetal side of the placenta and is covered by the AM. It is the innermost layer of the placenta and amniotic sac (Fig. 1). The AM is composed of two distinct layers: (1) the amnion that lines the inner surface of the amniotic sac facing the fetus; and (2) the chorion, that is, the layer in contact with the maternal tissue (decidua and myometrium) (Fig. 2). The amnion layer is composed of a simple squamous epithelium with an underlying basement membrane and a band of loose connective tissues. The connective tissues of the amnion and chorion are distinct, with the amnion layer only weakly attached to the underlying chorion (Fig. 3).6,7
Fig. 1: Diagram of amniotic sac and placenta
Fig. 2: Histology of the amniotic sac. Image provided by Jeffery Sussman, MD
Fig. 3: Amniotic membrane graft used to prevent nerve adhesion after a tarsal tunnel release. The AM graft is wrapped over the lateral/medial neve branch point of the posterior tibial nerve. Image provided by Gregory R Waryasz, MD
The umbilical cord ensures an exchange of blood between the mother and fetus, providing oxygenated blood to the fetus and removing by-products to the maternal circulation. The umbilical cord consists of the umbilical vessels (one vein and two arteries) and a bulk of mucous connective tissues known as Wharton’s jelly.8 Umbilical cord blood is the blood that remains in the placenta and umbilical cord following childbirth and is rich in hematopoietic stem cells, similar to those found in the bone marrow.9 The amniotic fluid (AF) envelopes the developing fetus within the amniotic sac and provides nutritional and immunomodulatory support to the growing fetus in the utero.7
PROCUREMENT AND PROCESSING OF THE AM AND PLACENTA
The placenta, umbilical cord, and umbilical cord blood have all emerged as an area of interest in cell-based therapy and regenerative medicine. The subject of placental-derived-tissue grafts is broad and several different formulations are available. Stromal cells isolated from each of the layers of the placenta differ, but most of the studies evaluating AM in foot and ankle pathology use the amnion layer alone, or a combination of the amnion and chorion layers.7,10,11
Amniotic membrane (AM)-derived products are harvested from donated placenta tissues with full consent from the mother.1,7,12,13 Cesarean delivery is preferred to eliminate the risk of contamination from normal flora during vaginal delivery.13 The collected placental membrane grafts are then aseptically processed, separated into individual membrane components, and then preserved.7,13,14
In the past decade, harvesting, processing, and preservation methods of AM grafts have dramatically improved, reducing the risk of disease transmission that once prevented their widespread use.1,15,16 Potential donors undergo strict screening protocols for hepatitis B and C, syphilis, cytomegalovirus, human immunodeficiency virus infection, and tuberculosis through regulation by the Federal Drug Administration (FDA) and the American Association of Tissue Banks.17,18
Methods of preservation have also led to the commercialization of placenta-derived products. Preservation methods include dehydration, cryopreservation, and lyophilization.1,19,20 The AM allografts used clinically for the nonoperative management of plantar fascia and Achilles pathology are mostly pulverized to particulate matter (i.e., micronized), cryopreserved, or lyophilized and are used as an injectable amniotic allograft.1,13 AM can also be processed to form sheets of tissues that can be used intraoperatively as tendons, ligaments, or nerve wraps.13,21 These sheets can also be deployed intratendinously during interventional procedures.
Methods of sterilization and preservation of placental tissues render themselves safe off-the-shelf products but can damage components of the placental tissues. Dehydration, cryopreservation, and lyophilization have been shown to preserve the structures of the basement membrane, which seems to allow AM products to serve as a scaffold and allow cell adhesion.22,23 Although some cryopreservation and lyopreservation processing methods may result in products containing viable cells, most commercially available products do not contain viable cells.1,23-29
BASIC SCIENCE OF AMNIOTIC GRAFTS: IN VITRO EFFECTS AND ANIMAL MODELS
Amniotic membranes (AMs) are a rich source of stem cells, including amniotic epithelial cells (AECs) and amniotic mesenchymal stromal cells (AMSCs). AECs have markers consistent with epithelial cells and stem cells and have the ability to differentiate into all of the mature cell lineages, including mesoderm, endoderm, and ectoderm.30 AMSCs are derived from the embryonic mesoderm and also have the ability to differentiate into all three germ layers.31 While AMSCs are known to be present in AF in vivo, the majority of commercial products have shown no living AMSCs after commercial processing (i.e., decellularization).24,25 Therefore, AM grafts should not be considered a mesenchymal “stem cell” product, as the cellular component of most commercial products is no longer viable after commercial processing.
Despite a lack of viable cells in most commercial products, the clinical benefits of AM-derived products seem to be maintained, suggesting that the effects are likely mediated by matrix proteins and growth factors within the AM-derived tissue.24,25 AM products are more accurately classified as a metabolically active biologic scaffold, and clinical studies in chronic wound management have demonstrated that placental products that contain viable cells result in similar wound closure rates as devitalized products.32,33
The mechanism of action of AM products likely varies depending on the underlying pathology. AM allografts are believed to aid in tissue repair by providing key growth factors to guide the connective tissues through the different phases of tissue repair. The release of vascular endothelial growth factors promotes angiogenesis, basic fibroblast growth factors promote early tendon healing, and transforming growth factor β stimulates the production of extracellular matrix.23,34
In vitro, AM has been shown to release anti-inflammatory cytokines, such as interleukin-10 (IL-10). These cytokines downregulate the inflammatory phase of healing, which is important in guiding tissue recovery and reducing scar tissue formation. In peripheral neuropathy, local inflammation triggers a cascade of processes that results in perineural fibrosis, scar formation, and adhesion.35 Anti-inflammatory cytokines contained in AM, such as IL-1 receptor antagonist and IL-10, can also downregulate inflammation to attenuate scar formation around the nerve.14,35 Anti-inflammatory cytokines contained in AM can also downregulate inflammation to attenuate cartilage degeneration.14,35 Synovial fluid in OA contains a high concentration of inflammatory cytokines, such as IL-1 and tumor necrotic factor-α. These cytokines cause an increased production of matrix metalloproteinase (MMP) that contributes to cartilage degradation. AM releases tissue inhibitors of metalloproteinase that reduce MMP activity and inhibits further collagen degradation.23
Animal studies have varied in the type of animal models used, pathology and indications, placental cell types, tissue preparation and preservation, doses, and administration routes. It is challenging to perform a comparative analysis, and a review of these preclinical animal studies is beyond the scope of this publication. In one review of 35 animal studies using AM-derived grafts, all reviewed publications demonstrated some degree of efficacy when treated with orthopedic sports medicine indications and when compared with controls.36
APPLICATIONS IN FOOT AND ANKLE ORTHOPEDICS
The clinical literature of the use on AM-derived allografts in orthopedics and sports medicine is limited. Human studies using AM allografts have been published for the treatment of plantar fasciitis, Achilles tendonitis, and knee OA. While AM has been used clinically for the treatment of OA in the foot, ankle, and nerve wrapping, to the authors’ knowledge, there are no publications describing clinical outcomes for these indications.
Plantar Fasciitis
Current treatment for plantar fasciitis is typically conservative and can include rest, physical therapy, orthoses, nonsteroidal anti-inflammatory drugs (NSAIDs), and corticosteroid injections.37,38 In 90% of the cases, symptoms are self-limiting and are resolved within 12 months with conservative treatments.39 Operative treatment is indicated in recalcitrant cases, although there is no consensus on the preferred operative technique since no procedure has demonstrated superior results.40
Several randomized controlled trials have shown a significant improvement in function and pain with AM graft injections for the treatment of chronic plantar fasciitis. Zelen et al. performed a randomized single-center clinical trial consisting of 45 patients, who were randomly divided into a control group (normal saline) and two treatment groups that received different volumes of acellular human AF. Both treatment groups had a significant improvement in pain and function as assessed by the American Orthopaedic Foot and Ankle Society (AOFAS) Hindfoot scores and Short Form 36 Standard Health Survey from their respective baseline levels at all-time points when compared to the control group, and the improvement was maintained at the 8-week follow-up.41 There are several concerns with this study. First, this was a small study with a relatively short follow-up and was funded by the AM manufacturer MiMedex. After the injections, the subjects were managed with orthosis, night splints, and tramadol, which could have potentially affected the outcomes.
Cazzell et al. conducted a prospective randomized multicenter clinical trial consisting of 145 patients, comparing a control group (normal saline injections) to a group that received micronized dehydrated human amnion/chorion membrane (mdHACM) injections. The patients were followed at various points over a year. The micronized amniotic injection group had significant improvement in pain and function as measured by the foot function index-revised (FFI-R) scores.37 This study is the largest randomized controlled study to date with an adequate follow-up and showed statistically significant improvements in pain and function. However, similar concerns exist for this study, including the fact that all patients were instructed to off-load their heels and to use night splints or orthotics. This study was also funded by MiMedex.
Hanselman et al. compared the efficacy of acellular human AF injections to that of corticosteroid injections and there was no significant difference in pain or function between the groups at the 6, 12, or 18-week follow-up.42 This study suggested that the efficacy of AM for the treatment of plantar fasciitis is at least comparable to that of corticosteroid injection, in terms of providing pain relief in the short and intermediate terms. However, unlike corticosteroid injections, AM may stimulate a reparative process that can provide long-term benefits with continued improvement seen at the long-term follow-up. This study was a low-powered pilot study (only 23 patients) with a short follow-up period. Patients were instructed to perform stretching exercises for the plantar fascia and calf at least five times a day, which may have had impactful results. This study was also funded by an AM manufacturer Amniox Medical, Inc.
Although there is promising evidence for using AM for plantar fasciitis, further high-quality studies are needed to establish its clinical utility. Overall, three randomized trials exist, but only one of these studies was adequately powered and reported long-term follow-up data. These studies suggest AM-derived products are either superior to placebo or noninferior over corticosteroid injections, but the results need to be interpreted carefully as various postintervention treatments were also used following the injections. Furthermore, all these studies were funded by manufacturers of AM.
Achilles Tendinopathy
Conservative treatments for Achilles tendonitis include physical therapy, rest, stretch exercise, NSAIDs, and steroid injections.43,44 Until recently, the use of AM graft for tendon repair was limited to in vivo studies.
In the past few years, several human clinical trials have been published, mostly as case series. In a series of patients (n = 44) experiencing recalcitrant Achilles tendinosis, Werber applied 1.0 mL of AM allograft along the tendon under ultrasound guidance. There was a significant reduction in pain scores starting in 4th week after the treatment, and most patients reported only mild pain by the 12thweek.43
Lullove published a series of 10 patients with various chronic tendon pathologies treated with human placental tissue. The composition of the placental tissue allograft was not reported in this publication or on the manufacturer’s website. All 10 patients had complete resolution of pain 5 weeks after the treatment. The study included two patients with Achilles tendonitis.
In a similar study, Gellhorn and Han conducted a case series of 40 patients with various chronic tendinosis or arthropathy who received mdHACM injections. This study included two patients with Achilles tendonitis. The cohort showed a significant reduction in average pain, starting 1 month after the procedure, with a significant improvement in functional levels. No serious adverse events occurred during the study.45
Finally, Spector et al. published a case series of 32 patients with Achilles tendinopathy treated with mdHACM. The study only reported short-term follow-ups. They found that while 97% of the patients reported severe or moderate pain prior to the intervention, 66% of treated patients reported complete symptom resolution, and the remaining reported partial improvement at the 45-day follow-up.46
The existing data seems to suggest that AM-derived products may be effective for chronic Achilles tendinopathy, but further high-quality studies are needed. The existing studies lack power and provide no long-term follow-up. No randomized controlled trials exist to date.
Osteoarthritis
Conventional management for OA includes weight loss, low impact aerobic exercise, physical therapy, NSAIDs, and steroid or hyaluronic acid injection.47 Surgical intervention is performed when these conventional managements are unsuccessful.47 Most of the studies using AM for the treatment of OA are for the knee and used micronized lyophilized, cryopreserved, or dehydrated AM or AF.45,48-52 Overall, these studies suggest that there is promising evidence for using AM to treat knee OA. Complications were limited to localized pain and swelling in a very small number of subjects. The one randomized trial by Gomoll et al. for knee OA has adequate power with an adequate follow-up period. This study suggested that AM may be superior to hyaluronic acid injection. It is important to note that most of these studies were funded by manufacturers of AM, and no studies have been published on AM allograft injections for ankle or foot OA.
Nerve Entrapment or Injury
Several in vivo studies have demonstrated AM’s anti-inflammatory and antifibrotic properties when used for peripheral nerve pathology.53-55 Autologous nerve grafts are a standard surgical technique for partial or complete loss of nerve function.54 Postoperative perineural scar formation and undesired adhesion can result in painful dysesthesias with progressive functional loss of the nerve.53 AM allografts’ anti-inflammatory and anti-scarring properties make AM allografts a promising candidate for nerve wrapping, but studies in human subjects remain limited. While the application of AM nerve allografts has not been reported in the foot and ankle literature, this application has been studied in the upper extremity. Gaspar et al. treated entrapped radial nerve sensory branch (n = 2) and cubital tunnel syndrome (n = 8) using revision neurolysis with AM nerve wrapping and demonstrated improvements in subjective pain and functional scores (Table 1).35,56
| Pathology | Study type | Allograft type | Duration | Summary | |
|---|---|---|---|---|---|
| Zelen et al.41 | Plantar fasciitis | Prospective, randomized (N = 45) | mdHACM a(AmnioFix Injectable, MiMedx) | 8 weeks | AOFAS and pain scores improved with the treatment within 1 week of treatment compared to saline injections. No adverse events related to the treatments were observed. |
| Hanselman et al.42 | Plantar fasciitis | Prospective, randomized (N = 23) | mdHACM (Clarix FLO, Medcore Biologix) | 12 weeks | No difference between cryopreserved AM and corticosteroid injections. No adverse events related to the treatments were observed. |
| Werber43 | Plantar fasciitis and Achilles tendonitis | Case series (N = 44) | Cryopreserved human AM-AF (PalinGen SportFLOW, Amnio Technology) | 12 weeks | Pain scores improved 4 weeks after the treatment with AM-AF. No adverse events related to the treatments were observed. |
| Lullove65 | Various tendinopathies | Retrospective case series (N = 10) | Human placental tissue b(PX50, Human Regenerative Technologies LLC) | 6 weeks | By the 5th week, all 10 patients had resolved their pain. |
| Gellhorn and Han45 | Various tendon and joint pathologies | Case series (N = 40) | mdHACM a(AmnioFix Injectable, MiMedx) | 12 weeks | Pain scores improved 4 weeks after the treatment. No serious adverse events related to the treatments were observed. |
| Cazzell et al.37 | Plantar fasciitis | Prospective, randomized (N = 145) | mdHACM a(AmnioFix Injectable, MiMedx) | 12 weeks | FFI-R and pain scores improved 3 months after the treatment compared to placebo. No adverse events related to the treatments were observed. |
| Spector et al.46 | Achilles tendonitis | Retrospective case series (N = 32) | mdHACM a(AmnioFix Injectable, MiMedx) | 4 weeks | All patients reported either complete symptom resolution or partial symptom improvement after the treatment. No adverse events related to the treatments were observed. |
| Chin and LaViolette66 | Achilles tendonitis | Retrospective case series (N = 10) | mdHACM (Clarix FLO, Medcore Biologix) | 12 months | Pain scores improved 4 weeks after the treatment. No adverse events related to the treatments were observed. |
aNo longer available in the market; bFormulation not clear in the publication or on the manufacturer’s website
APPLICATIONS OUTSIDE OF ORTHOPEDIC PRACTICE
Based on the number of clinical trials and publications, orthopedics is the field in which AM is the second most used. AM tissue has been most used in the field of dermatology and wound care.57 AM allograft, when applied to wound tissue, has been found to promote collagen secretion and angiogenesis.58,59 Other fields that use AM include ophthalmology, urology, neurology, dentistry, otolaryngology, and hematology/oncology.57
SAFETY OF AM ALLOGRAFTS
Concerns over the safety of AM-derived products include a lack of standardization in both the content and administration of these products.60 The content of commercially available AM grafts has not been well studied, and equivalency cannot be assumed among the different commercial manufacturers.25 The level of growth factors has been shown to be lower in commercially available AM-derived products than in unprocessed AF.25 AM products represent varying mixtures of different tissue components, and there appears to be no unified approach to preparation or storage.12 In addition, some of the products used in many of the clinical studies (i.e., AmnioFix Injectables) are no longer commercially available, and thus, clinicians need to be cautious about making generalized conclusions from the published studies.
There are limited human studies assessing the safety of AM-derived products for musculoskeletal indications. AM tissue is characterized by its low immunogenicity, which theoretically improves its safety profile. During gestation, AM tissues arise from the inner cell mass and should theoretically be recognized as foreign tissue in the maternal environment. However, the maternal immune system demonstrates tolerance for AM tissue.5 The immunomodulatory properties of AM appear to be due to the lack of major histocompatible antigens (human leukocyte antigens A, B, C, or DR) on the surface epithelial cells.61,62 Current literature suggests that acute rejection does not occur even when used for severely immunocompromised patients.43 In another study, when a monolayer of human AEC was transplanted into healthy volunteers, there was no evidence of acute rejections.63
Despite the privileged immune status of AM-derived cells and existing literature, there is some concern that commercially available products may retain either viable or fractured cells, which may result in an immune cascade of unknown consequence.27,60 Further high-quality supportive data on safety are necessary to address these concerns.
REGULATORY CONSIDERATIONS
In 2017, the United States FDA published a framework for regulating regenerative medicine products under the authority of the Public Health Service Act (PHSA).64 These regulations govern human cells, tissues, and cellular and tissue-based products (HCT/Ps), defined as “articles containing or consisting of human cells or tissues that are intended for implantation, transplantation, infusion, or transfer into a human recipient.”64 HCT/P can be allografts (grafts taken from a donor, i.e., placenta-derived products) or autologous grafts taken from the patient’s own body (i.e., autologous whole blood, platelet-rich plasma, bone marrow concentrate, and adipose-derived grafts).
The regulations set forth in the Code of Federal Regulations, Title 21, Part 1271 regulate whether the HCT/P product is classified and regulated as a biologic drug (Section 351 of the PHSA) or whether the product can be used without premarket approval from the FDA (Section 361 of the PHSA).64 Products that are deemed a “361 HCT/P” must satisfy the following four criteria set forth by the FDA and can avoid the costly and time-consuming process of an FDA review and licensure. These criteria include: (1) minimal manipulation; (2) homologous use; (3) not combined with drugs or devices; (4) and not reliant on cell metabolic activity as a primary function.65 If the product does not meet all these criteria, the product is deemed a “351 HCT/P,” and these products constitute a “biologic product” that requires FDA review and licensure under the PHSA.66
Currently, there are no 351 HCT/P placenta-based biological drugs that have been approved by the FDA in the United States. AM-derived products that are flowable or micronized formulations are considered beyond minimal manipulation and, as of 31st May 2021, require FDA review under Section 351. These 351 HCT/Ps are now required to file for an Investigational New Drug (IND) application and conduct phase 1–2 clinical trials. At this time, no flowable amniotic product, umbilical cord blood, Wharton jelly, or exosomes should be administered to a patient that is not enrolled in an IND study with the physician acting as a listed investigator on the study. AM-derived allograft products that are minimally manipulated and used for homologous use (i.e., “repair, reconstruction, replacement, or supplementation of a recipient’s cells or tissues via implantation, transplantation, infusion, or transfer into a human recipient”) are regulated as 361 HCT/P products. These products include sheet amnion, sheet chorion, and sheet amnion/chorion products.
The regulatory status of individual AM-derived products may change as companies pursue approval for various biologic products through the Center for Biologics Evaluation and Research. Clinicians in the United States should be aware of the regulatory environment and the status of any AM-derived product before using the product in clinical practice. Furthermore, as AM remains an investigational drug, it is difficult to comment on its cost implications at this time. The direct cost of AM allografts is typically not covered by insurance.
CONCLUSION
Amniotic membrane (AM)-derived products have shown promise in the field of orthopedics and sports medicine, although the literature remains limited. The existing studies suggest that the efficacy of AM-derived products is at least equivocal to corticosteroid injections in the short-term and demonstrated superiority to placebo injections for plantar fasciitis in long-term follow-up (i.e., 1 year). Fewer studies have explored the application of AM-derived products in Achilles tendinitis, ankle and foot OA, or peripheral nerve pathology. Additional high-quality supportive data is needed to support the efficacy and safety of AM-derived products in foot and ankle pathology. Despite promising preclinical data and clinical interest in AM-derived products, regulatory concerns in the United States may limit the clinical application of AM-derived products. Currently, no commercially available AM products have been approved by the FDA as a “biologic drug,” and clinicians should be aware of the regulatory status of any AM-derived product before use in clinical practice.
ORCID
Hirotaka Nakagawa https://orcid.org/0000-0002-7491-4986
Soheil Ashkani-Esfahani https://orcid.org/0000-0003-2299-6278
REFERENCES
1. Ang J, Liou CD, Schneider HP. The role of placental membrane allografts in the surgical treatment of tendinopathies. Clin Podiatr Med Surg 2018;35(3):311–321. DOI: 10.1016/j.cpm.2018.02.004
2. Rahman I, Said DG, Maharajan VS, et al. Amniotic membrane in ophthalmology: indications and limitations. Eye (Lond) 2009;23(10):1954–1961. DOI: 10.1038/eye.2008.410
3. Malhotra C, Jain AK. Human amniotic membrane transplantation: different modalities of its use in ophthalmology. World J Transplant 2014;4(2):111–121. DOI: 10.5500/wjt.v4.i2.111
4. Lintzeris D, Yarrow K, Johnson L, et al. Use of a dehydrated amniotic membrane allograft on lower extremity ulcers in patients with challenging wounds: a retrospective case series. Ostomy Wound Manage 2015;61(10):30–36. PMID: 26479124.
5. Liu J, Sheha H, Fu Y, et al. Update on amniotic membrane transplantation. Expert Rev Ophthalmol 2010;5(5):645–661. DOI: 10.1586/eop.10.63
6. Strauss JF 3rd. Extracellular matrix dynamics and fetal membrane rupture. Reprod Sci 2013;20(2):140–153. DOI: 10.1177/1933719111424454
7. Hanselman AE, Lalli TA, Santrock RD. Topical review: use of fetal tissue in foot and ankle surgery. Foot Ankle Spec 2015;8(4):297–304. DOI: 10.1177/1938640015578513
8. Ferguson VL, Dodson RB. Bioengineering aspects of the umbilical cord. Eur J Obstet Gynecol Reprod Biol 2009;144(Suppl 1):S108–S113. DOI: 10.1016/j.ejogrb.2009.02.024
9. Harris DT, Rogers I. Umbilical cord blood: a unique source of pluripotent stem cells for regenerative medicine. Curr Stem Cell Res Ther 2007;2(4):301–309. DOI: 10.2174/157488807782793790
10. Choi YS, Park YB, Ha CW, et al. Different characteristics of mesenchymal stem cells isolated from different layers of full term placenta. PLoS One 2017;12(2):e0172642. DOI: 10.1371/journal.pone.0172642
11. Indumathi S, Harikrishnan R, Mishra R, et al. Comparison of feto-maternal organ derived stem cells in facets of immunophenotype, proliferation and differentiation. Tissue Cell 2013;45(6):434–442. DOI: 10.1016/j.tice.2013.07.007
12. Riboh JC, Saltzman BM, Yanke AB, et al. Human amniotic membrane-derived products in sports medicine: basic science, early results, and potential clinical applications. Am J Sports Med 2016;44(9):2425–2434. DOI: 10.1177/0363546515612750
13. Leal-Marin S, Kern T, Hofmann N, et al. Human amniotic membrane: a review on tissue engineering, application, and storage. J Biomed Mater Res B Appl Biomater 2021;109(8):1198–1215. DOI: 10.1002/jbm.b.34782
14. Huddleston HP, Cohn MR, Haunschild ED, et al. Amniotic product treatments: clinical and basic science evidence. Curr Rev Musculoskelet Med 2020;13(2):148–154. DOI: 10.1007/s12178-020-09614-2
15. John T. Human amniotic membrane transplantation: past, present, and future. Ophthalmol Clin North Am 2003;16(1):43–65. DOI: 10.1016/s0896-1549(02)00110-4
16. Fetterolf DE, Snyder RJ. Scientific and clinical support for the use of dehydrated amniotic membrane in wound management. Wounds 2012;24(10):299–307. PMID: 25876055.
17. Kesting MR, Wolff KD, Hohlweg-Majert B, et al. The role of allogenic amniotic membrane in burn treatment. J Burn Care Res 2008;29(6):907–916. DOI: 10.1097/BCR.0b013e31818b9e40
18. Food and Drug Administration, HHS. Current good tissue practice for human cell, tissue, and cellular and tissue-based product establishments; inspection and enforcement. Final rule. Fed Regist 2004;69(226):68611–68688. PMID: 15562555
19. Rodriguez-Ares MT, Lopez-Valladares MJ, Tourino R, et al. Effects of lyophilization on human amniotic membrane. Acta Ophthalmol 2009;87(4):396–403. DOI: 10.1111/j.1755-3768.2008.01261.x
20. Nakamura T, Yoshitani M, Rigby H, et al. Sterilized, freeze-dried amniotic membrane: a useful substrate for ocular surface reconstruction. Invest Ophthalmol Vis Sci 2004;45(1):93–99. DOI: 10.1167/iovs.03-0752
21. Liu C, Bai J, Yu K, et al. Biological amnion prevents flexor tendon adhesion in zone II: a controlled, multicentre clinical trial. Biomed Res Int 2019;2019:2354325. DOI: 10.1155/2019/2354325
22. Niknejad H, Deihim T, Solati-Hashjin M, et al. The effects of preservation procedures on amniotic membrane’s ability to serve as a substrate for cultivation of endothelial cells. Cryobiology 2011;63(3):145–151. DOI: 10.1016/j.cryobiol.2011.08.003
23. Koob TJ, Rennert R, Zabek N, et al. Biological properties of dehydrated human amnion/chorion composite graft: implications for chronic wound healing. Int Wound J 2013;10(5):493–500. DOI: 10.1111/iwj.12140
24. Becktell L, Matuska AM, Hon S, et al. Proteomic analysis and cell viability of nine amnion, chorion, umbilical cord, and amniotic fluid-derived products. Cartilage 2021;13(2):495S–507S. DOI: 10.1177/1947603520976767
25. Panero AJ, Hirahara AM, Andersen WJ, et al. Are amniotic fluid products stem cell therapies? A study of amniotic fluid preparations for mesenchymal stem cells with bone marrow comparison. Am J Sports Med 2019;47(5):1230–1235. DOI: 10.1177/0363546519829034
26. Hennerbichler S, Reichl B, Pleiner D, et al. The influence of various storage conditions on cell viability in amniotic membrane. Cell Tissue Bank 2007;8(1):1–8. DOI: 10.1007/s10561-006-9002-3
27. Mao Y, Hoffman T, Dhall S, et al. Endogenous viable cells in lyopreserved amnion retain differentiation potential and anti-fibrotic activity in vitro. Acta Biomater 2019;94:330–339. DOI: 10.1016/j.actbio.2019.06.002
28. Jacob V, Johnson N, Lerch A, et al. Structural and functional equivalency between lyopreserved and cryopreserved chorions with viable cells. Adv Wound Care (New Rochelle) 2020;9(9):502–515. DOI: 10.1089/wound.2019.1041
29. Johnson A, Gyurdieva A, Dhall S, et al. Understanding the impact of preservation methods on the integrity and functionality of placental allografts. Ann Plast Surg 2017;79(2):203–213. DOI: 10.1097/sap.0000000000001101
30. Miki T. Stem cell characteristics and the therapeutic potential of amniotic epithelial cells. Am J Reprod Immunol 2018;80(4):e13003. DOI: 10.1111/aji.13003
31. Zhang Y, Li C, Jiang X, et al. Human placenta-derived mesenchymal progenitor cells support culture expansion of long-term culture-initiating cells from cord blood CD34+ cells. Exp Hematol 2004;32(7):657–664. DOI: 10.1016/j.exphem.2004.04.001
32. Lavery LA, Fulmer J, Shebetka KA, et al. The efficacy and safety of Grafix(®) for the treatment of chronic diabetic foot ulcers: results of a multi-centre, controlled, randomised, blinded, clinical trial. Int Wound J 2014;11(5):554–560. DOI: 10.1111/iwj.12329
33. Frykberg RG, Gibbons GW, Walters JL, et al. A prospective, multicentre, open-label, single-arm clinical trial for treatment of chronic complex diabetic foot wounds with exposed tendon and/or bone: positive clinical outcomes of viable cryopreserved human placental membrane. Int Wound J 2017;14(3):569–577. DOI: 10.1111/iwj.12649
34. Koob TJ, Lim JJ, Massee M, et al. Angiogenic properties of dehydrated human amnion/chorion allografts: therapeutic potential for soft tissue repair and regeneration. Vasc Cell 2014;6:10. DOI: 10.1186/2045-824X-6-10
35. Gaspar MP, Abdelfattah HM, Welch IW, et al. Recurrent cubital tunnel syndrome treated with revision neurolysis and amniotic membrane nerve wrapping. J Shoulder Elbow Surg 2016;25(12):2057–2065. DOI: 10.1016/j.jse.2016.09.013
36. McIntyre JA, Jones IA, Danilkovich A, et al. The placenta: applications in orthopaedic sports medicine. Am J Sports Med 2018;46(1):234–247. DOI: 10.1177/0363546517697682
37. Cazzell S, Stewart J, Agnew PS, et al. Randomized controlled trial of micronized dehydrated human amnion/chorion membrane (dHACM) injection compared to placebo for the treatment of plantar fasciitis. Foot Ankle Int 2018;39(10):1151–1161. DOI: 10.1177/1071100718788549
38. Radwan YA, Mansour AM, Badawy WS. Resistant plantar fasciopathy: shock wave versus endoscopic plantar fascial release. Int Orthop 2012;36(10):2147–2156. DOI: 10.1007/s00264-012-1608-4
39. Monteagudo M, de Albornoz PM, Gutierrez B, et al. Plantar fasciopathy: a current concepts review. EFORT Open Rev 2018;3(8):485–493. DOI: 10.1302/2058-5241.3.170080
40. Latt LD, Jaffe DE, Tang Y, et al. Evaluation and treatment of chronic plantar fasciitis. Foot Ankle Orthop 2020;5(1):2473011419896763. DOI: 10.1177/2473011419896763
41. Zelen CM, Poka A, Andrews J. Prospective, randomized, blinded, comparative study of injectable micronized dehydrated amniotic/chorionic membrane allograft for plantar fasciitis–a feasibility study. Foot Ankle Int 2013;34(10):1332–1339. DOI: 10.1177/1071100713502179
42. Hanselman AE, Tidwell JE, Santrock RD. Cryopreserved human amniotic membrane injection for plantar fasciitis: a randomized, controlled, double-blind pilot study. Foot Ankle Int 2015;36(2):151–158. DOI: 10.1177/1071100714552824
43. Werber B. Amniotic tissues for the treatment of chronic plantar fasciosis and Achilles tendinosis. J Sports Med (Hindawi Publ Corp) 2015;2015:219896. DOI: 10.1155/2015/219896
44. Skjong CC, Meininger AK, Ho SS. Tendinopathy treatment: where is the evidence? Clin Sports Med 2012;31(2):329–350. DOI: 10.1016/j.csm.2011.11.003
45. Gellhorn AC, Han A. The use of dehydrated human amnion/chorion membrane allograft injection for the treatment of tendinopathy or arthritis: a case series involving 40 patients. PM R 2017;9(12):1236–1243. DOI: 10.1016/j.pmrj.2017.04.011
46. Spector JE, Hubbs B, Kot K, et al. Micronized dehydrated human amnion/chorion membrane injection in the treatment of chronic Achilles tendinitis. J Am Podiatr Med Assoc 2021;111(6). DOI: 10.7547/19-170
47. Jang S, Lee K, Ju JH. Recent updates of diagnosis, pathophysiology, and treatment on osteoarthritis of the knee. Int J Mol Sci 2021;22(5):2619. DOI: 10.3390/ijms22052619
48. Vines JB, Aliprantis AO, Gomoll AH, et al. Cryopreserved amniotic suspension for the treatment of knee osteoarthritis. J Knee Surg 2016;29(6):443–450. DOI: 10.1055/s-0035-1569481
49. Farr J, Gomoll AH, Yanke AB, et al. A randomized controlled single-blind study demonstrating superiority of amniotic suspension allograft injection over hyaluronic acid and saline control for modification of knee osteoarthritis symptoms. J Knee Surg 2019;32(11):1143–1154. DOI: 10.1055/s-0039-1696672
50. Gomoll AH, Farr J, Cole BJ, et al. Safety and efficacy of an amniotic suspension allograft injection over 12 months in a single-blinded, randomized controlled trial for symptomatic osteoarthritis of the knee. Arthroscopy 2021;37(7):2246–2257. DOI: 10.1016/j.arthro.2021.02.044
51. Alden KJ, Harris S, Hubbs B, et al. Micronized dehydrated human amnion chorion membrane injection in the treatment of knee osteoarthritis-a large retrospective case series. J Knee Surg 2021;34(8):841–845. DOI: 10.1055/s-0039-3400951
52. Castellanos R, Tighe S. Injectable amniotic membrane/umbilical cord particulate for knee osteoarthritis: a prospective, single-center pilot study. Pain Med 2019;20(11):2283–2291. DOI: 10.1093/pm/pnz143
53. Kim SS, Sohn SK, Lee KY, et al. Use of human amniotic membrane wrap in reducing perineural adhesions in a rabbit model of ulnar nerve neurorrhaphy. J Hand Surg Eur Vol 2010;35(3):214–219. DOI: 10.1177/1753193409352410
54. Meng H, Li M, You F, et al. Assessment of processed human amniotic membrane as a protective barrier in rat model of sciatic nerve injury. Neurosci Lett 2011;496(1):48–53. DOI: 10.1016/j.neulet.2011.03.090
55. Ozgenel GY, Fílíz G. Combined application of human amniotic membrane wrapping and hyaluronic acid injection in epineurectomized rat sciatic nerve. J Reconstr Microsurg 2004;20(2):153–157. DOI: 10.1055/s-2004-820772
56. Gaspar MP, Kane PM, Vosbikian MM, et al. Neurolysis with amniotic membrane nerve wrapping for treatment of secondary Wartenberg syndrome: a preliminary report. J Hand Surg Asian Pac Vol 2017;22(2):222–228. DOI: 10.1142/S0218810417200015
57. Nejad AR, Hamidieh AA, Amirkhani MA, et al. Update review on five top clinical applications of human amniotic membrane in regenerative medicine. Placenta 2021;103:104–119. DOI: 10.1016/j.placenta.2020.10.026
58. Ghalei S, Nourmohammadi J, Solouk A, et al. Enhanced cellular response elicited by addition of amniotic fluid to alginate hydrogel-electrospun silk fibroin fibers for potential wound dressing application. Colloids Surf B Biointerfaces 2018;172:82–89. DOI: 10.1016/j.colsurfb.2018.08.028
59. Gholipourmalekabadi M, Samadikuchaksaraei A, Seifalian AM, et al. Silk fibroin/amniotic membrane 3D bi-layered artificial skin. Biomed Mater 2018;13(3):035003. DOI: 10.1088/1748-605X/aa999b
60. Noridian. Amniotic Product Injections for Musculoskeletal Indications, Non-Wound Carrier Advisory Committee (CAC) Meeting - May 12, 2021. Accessed 4/26/2022, 2022. https://med.noridianmedicare.com/web/jea/policies/lcd/cac/cac-transcript-051221
61. Adinolfi M, Akle CA, McColl I, et al. Expression of HLA antigens, beta 2-microglobulin and enzymes by human amniotic epithelial cells. Nature 1982;295(5847):325–327. DOI: 10.1038/295325a0
62. Hsi BL, Yeh CJ, Faulk WP. Human amniochorion: tissue-specific markers, transferrin receptors and histocompatibility antigens. Placenta 1982;3(1):1–12. DOI: 10.1016/s0143-4004(82)80012-x
63. Akle CA, Adinolfi M, Welsh KI, et al. Immunogenicity of human amniotic epithelial cells after transplantation into volunteers. Lancet 1981;2(8254):1003–1005. DOI: 10.1016/s0140-6736(81)91212-5
64. CFR - Code of Federal Regulations Title 21. https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?CFRPart=1271&showFR=1
65. Lullove E. A flowable placental tissue matrix allograft in lower extremity injuries: a pilot study. Cureus 2015;7(6):e275. DOI: 10.7759/cureus.275
66. Chin MJ, LaViolette K. Amniotic membrane/ umbilical cord particulate injection for Achilles tendinopathy with or without a partial tear. FASTRC 2022;2(2):100169. DOI: 10.1016/j.fastrc.2022.100169
________________________
© The Author(s). 2023 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted use, distribution, and non-commercial reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.