Introduction
Diabetes mellitus (DM) is a worldwide epidemic disease. In 2019, the global diabetes prevalence was projected to be 9.3% (463 million people). The prevalence is estimated to rise to 10.2% (578 million) by 2030 and 10.9% (700 million) by 2045 [
1]. Diabetic foot ulcer (DFU) is one of the most serious and common complications of diabetes that itself can be complicated by wound infection, gangrene, and unfortunate amputation. Amputation can comprise a huge burden on the patients' quality of life and the health systems' economy [
2]. The global prevalence of DFU is 6.3%, affecting males more than females, and patients with type 2 DM more than type 1 [
3]. Diabetic foot ulcer is primarily caused by hyperglycemia that results from endothelial dysfunction, leading to vascular insufficiency and nerve injury [
4,
5].
The current DFU standard of care (SOC) involves four principles; pressure relief, debridement, infection management, and revascularization when indicated. Preventative measures such as adequate glycemic control, periodic foot inspection, as well as patient and family education are always recommended [
6,
7]. Sometimes the SOC is not enough for the management of DFUs, therefore, new trends have emerged to address this problem. These include negative pressure wound therapy, hyperbaric oxygen therapy, bioengineered skin substitutes, and shockwave therapy, among several other measures. These novel therapies have shown significant DFU clinical improvement in different subsets of DFU. However, much of the literature came from smaller trials with inconsistent patient selection and outcomes measurement, making it difficult to assess the exact clinical benefit of these treatments [
7].
Although we associate regenerative medicine with the recent decades, amnion has been used in the medical field for over a century. The first known usage for amnion was in a skin transplant, in 1910 at John Hopkins Hospital [
8]. Dehydrated human amnion-chorion membranes and placenta possess marvelous features, from the pluripotent stem cells which can differentiate into all three germ layers, to the angiogenic anti-inflammatory properties coming from a wide variety and mixture of angio-modulatory cytokines, anti-bacterial peptides, and anti-inflammatory agents [
9,
10]. These membranes are currently considered a new hope in regenerative medicine owing to their wide uses, low immunogenicity, and easy procurement from the placenta. As the placenta is a discarded tissue after parturition, the current controversies associated with the use of human embryonic stem cells are avoided [
11].
Dehydrated human amniotic and chorionic allograft (DHACA) is easier for application and commercially available. This product can be applied directly to clean the debrided wounds where the infection has been controlled and adequate vasculature and perfusion state exist, to achieve wound healing as early as possible [
12]. Many studies have shown that DHACA as a treatment for diabetic foot ulcers is more effective than standard wound care alone. For further evaluation of the efficacy and time-sensitivity of DHACAs in patients suffering from DFU, we performed this systematic review and meta-analysis study. Our study compares using DHACA plus SOC versus SOC alone.
Material and methods
We performed a systematic review and meta-analysis for clinical trials on the use of dehydrated human amnion/chorion membrane for the treatment of DFU. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines in reporting our study [
13].
Search strategy
We used four different databases for the literature search (PubMed, Scopus, Cochrane and Web of Science), and the search was conducted from their inception till October 2020. The following keywords were used (Diabetic foot ulcer, human amnion membrane, amniotic allograft, Grafix, AmnioBand, EpiFix), and MESH terms were used when applicable. We also did a manual screening of references in the included studies, searching for any relevant trials.
Inclusion and exclusion criteria
English-written human-based randomized clinical trials (RCTs) were included in our study. Diabetic patients with foot ulcers were the target population. The intervention was human amnion, chorion, placental membrane, or any brand using them like Grafix, GrafixPL PRIME, AmnioBand, Stravix, biological dressing, bio implant dressing, or EpiFix. The comparator was any effective measurement like SOC. We excluded conference abstracts, books, single-armed clinical trials, animal studies, and studies on non-diabetic patients.
Study selection
We used EndNote X8 for citation management and duplicate removal for articles identified in the searches. We selected the included studies in a two-stage screening process. In the first stage, the titles and abstracts from the electronic searches were screened independently. The second stage of full-text screening was performed to determine the final decision on studies' eligibility. The assessment of each manuscript was performed independently by at least three authors, and any disagreements about inclusion were resolved by consultation with the principal investigator of the study.
Quality assessment
The risk of bias was assessed according to the Cochrane risk of bias tool described in the Cochrane Handbook for Systematic Reviews of Interventions 5.1.0 [
14]. There are six domains in the tool: random sequence generation, allocation sequence concealment, blinding of study participants and personnel, blinding of outcome assessors, incomplete outcome data, selective outcomes reporting, and other potential sources of bias. We reported the quality of the included studies as low risk, high risk, or unclear risk of bias. In addition, we measured the publication bias through visualization of the funnel plot for any asymmetrical distribution [
15].
Each author – independently – extracted data from all the included trials. Data extraction was performed in an excel sheet that included three sections. Firstly, general data included the year of publication, protocol registration, definition of ulcers, groups and sample size, and intervention. Then, baseline data included age, race, gender, Body Mass Index (BMI), mean glycated hemoglobin, smoking, duration of wound, initial wound surface area in cm2, and wound location.
Primary and secondary outcomes
The primary outcomes were the percentage of complete wound healing by the 6th and 12th week and the mean time to heal within the 1st, 6th, and 12th weeks. The secondary outcomes included the Kaplan–Meier plot of time to heal within the 1st, 6th, and 12th week, and wound size reduction. An adverse events analysis was performed, including any unfavorable outcome that occurred to patients in each group during the time of the trial like (Cellulitis, osteomyelitis and infection of the affected extremity, development of another ulcer, deep vein thrombosis, urinary tract infection and gastrointestinal bleed).
Statistical analysis
We conducted the meta-analyses using the Review Manager (RevMan) computer program (Version 5.4. Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration, 2014). Regarding pooling of the study outcomes, risk ratio (RR) with the 95% confidence interval (CI) were used for dichotomous variables, while the mean difference (MD) and the 95% CI were presented for continuous variables. Cochrane's P values and the I2 were tested to examine heterogeneity among the included studies. High heterogeneity existed in some analyses most likely due to clinical and methodological factors, therefore, the random effect model was adopted in these analyses. Funnel plots and the Egger regression test were conducted and measured through visualization of the funnel plot. Besides, a sensitivity analysis was performed by sequentially deleting trials to check for the stability of the primary outcomes.
Discussion
This systematic review and meta-analysis is based on ten published RCTs [
12,
17,
18,
20‐
26] and one unpublished RCT (NCT03547635) that compared DHACA with SOC versus SOC alone in the treatment of DFUs. A total of 655 patients suffering from DFU were included in this systematic review. The meta-analysis findings showed that using DHACA with SOC is more effective and safer than the SOC alone for treating chronic DFUs. The pooled effect estimate of the 11 RCTs showed the superiority of the DHACA regarding complete wound healing in both the 6
th and 12
th weeks. The mean time for healing was not significantly different between the two groups at the 4
th and 6
th weeks, while a significant reduction in healing time was observed in the 12
th week favoring DHACA. Kaplan–Meier's plot of time to heal was significantly better in DHACA with SOC than SOC alone in the 1
st, 6
th, and 12
th weeks. Moreover, the current meta-analysis results revealed that DHACA can significantly reduce the wound size with a low risk of adverse events compared to SOC alone.
Similar to our findings, a previous meta-analysis [
27] reported that the incomplete wound healing outcomes are less associated with DHACA plus SOC group than SOC only group at the 4
th, 6
th, and 12
th weeks with significant P values of < 0.0001, < 0.0001, and < 0.0001 respectively. This meta-analysis was conducted on seven studies with a total sample size of 347 patients and was limited by assessing a single outcome (wound healing). Contrary to the previous meta-analysis [
27], our meta-analysis evaluated five outcomes: the percentage of complete wound healing, mean time to heal, Kaplan–Meier plot of time to heal, wound size reduction, and adverse events.
The human amniotic membrane is structured from three types of material: active cells, collagen fibers, extracellular matrix, and regenerative molecules. The amniotic membrane has been studied to investigate its effects on the wound healing process [
28]. DiDomenico et al. 2016 [
22] demonstrated that the mean and median time for wound healing is 12 weeks in the DHACA group, which was faster than most of the other cellular and/or tissue-based products (CTPs) reported in other RCTs [
21,
25,
28‐
35]. In the multicenter trial Reyzelman et al. [
31], 69.6% of the allograft has healed. While in Niezgoda et al. [
34] 49% of small intestine submucosal CTP has healed. These findings reflect that DHACA might be promising and the most effective CTPs available.
Wound infections developed in DFU patients have 56 times the risk of requiring hospitalization and 155 times the risk of requiring amputation when compared to other wounds [
36] . Once the patient’s foot or leg is amputated, an increase in the risk of repeated infections and ulcers arises [
37]. To achieve wound healing, a 100% epithelialization must occur without drainage or need for dressing [
23]. The main goal of DFU treatment is to enhance and facilitate complete wound healing; therefore, reducing the risk of complications such as infection, amputation, and delayed wound healing [
27].
For our included studies, Zelen et al. [
21] reported that complete wound healing occurred in 73%, 97%, and 51% of patients treated with bioengineered skin substitutes (BSS), dHACM, and SOC alone within 12 weeks, respectively. DiDomenico et al. 2016 [
23] & DiDomenico et al. 2018 [
22] showed that at the 12
th week, 85% of the DHACA-treated DFUs healed compared with 25% and 33% when treated with SOC alone, respectively. The mean time to heal ranged between 36 and 70 days in DiDomenico et al. 2016 [
23] and between 37 and 67 days in DiDomenico et al. 2018 [
22]. In addition, they concluded that the DHACA graft might have a sufficient clinical effect to be used in patients with more complex deep wounds that reach tendon and bone.
Lavery et al. [
25] reported that the incidence of adverse events was 44% in Grafix group versus 66% in the SOC group, and the wound-related infections were fewer in the Grafix group (18%) than in the SOC group (36.2%). Similar to these findings, Zelen et al. 2013 [
17] findings demonstrated that of patients who experienced DFU-related complications, 92% have healed with dehydrated human amniotic membrane allografts (EpiFix), while only 8% have healed with SOC alone. Zelen et al. 2015 [
24] compared the median time to wound healing in DFPs using EpiFix, Apligraf, and SOC, they found that the healing time was significantly faster in EpiFix (13 days) compared to Apligraf (49 days) or standard care (49 days).
This meta-analysis is based on RCTs, which is considered a point of strength, the findings should be cautiously interpreted due to several concerns. The first concern is that dietary factors that could vary in other populations might have affected the generalizability of the studies' results. The second concern is about the possibility of patients' overlap in included studies. The third concern is the high heterogeneity in some outcomes that could not be resolved. Including English studies only could be considered a limitation of the current review. In addition, a possible concern can arise in studies by Zelen et al. 2013 [
17], Zelen et al. 2015 [
24], and Zelen et al. 2016 [
21], also in DiDomenico et al. 2016 [
23] and DiDomenico et al. 2018 [
22] since these studies were conducted by the same authors. Therefore, future studies from different countries/populations are necessary to explore the effect of DHACA in treating DFUs in other populations.
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